Journal articles on the topic 'Petrologic analysis'
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1
Russell, J. K., and J. Nicholls. "Analysis of petrologic hypotheses with Pearce element ratios." Contributions to Mineralogy and Petrology 99, no. 1 (May 1988): 25–35. http://dx.doi.org/10.1007/bf00399362.
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Licht, Kathy J., and Sidney R. Hemming. "Analysis of Antarctic glacigenic sediment provenance through geochemical and petrologic applications." Quaternary Science Reviews 164 (May 2017): 1–24. http://dx.doi.org/10.1016/j.quascirev.2017.03.009.
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Cui, Tao. "Research Progress of Bauxite in WZD Area, Northern Guizhou, China." Advanced Materials Research 989-994 (July 2014): 1392–95. http://dx.doi.org/10.4028/www.scientific.net/amr.989-994.1392.
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This paper has a comprehensive analysis on the bauxite in Wuchuan-Zheng, an-Daozhen (WZD) area, northern Guizhou, China through synthesize former research. The understanding of mineralogic, petrologic and geochemical characteristics is deep, and sedimentary environment, parent rock and mineralization process have been defined. Main questions need further research as follow: minerogenetic epoch; migration mechanism of elements; genesis of rare earth mineral.
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Matarrese, Alejandra, Violeta Di Prado, and Daniel Gustavo Poiré. "Petrologic analysis of mineral pigments from hunter-gatherers archaeological contexts (Southeastern Pampean region, Argentina)." Quaternary International 245, no. 1 (November 2011): 2–12. http://dx.doi.org/10.1016/j.quaint.2010.11.005.
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Cantner, Kathleen, Steven Carey, and Paraskevi Nomikou. "Integrated volcanologic and petrologic analysis of the 1650AD eruption of Kolumbo submarine volcano, Greece." Journal of Volcanology and Geothermal Research 269 (January 2014): 28–43. http://dx.doi.org/10.1016/j.jvolgeores.2013.10.004.
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Seixas, Teresa M., Bruno Almeida, Maria H. Mendes, Manuel A. Salgueiro da Silva, José F. Santos, Fernando Almeida, Zenaida Diogo, Augusto B. Lopes, and Joaquim M. Vieira. "XRD, SEM and Petrologic Characterization of a L4-L5 Ordinary Chondrite Meteorite." Materials Science Forum 730-732 (November 2012): 170–75. http://dx.doi.org/10.4028/www.scientific.net/msf.730-732.170.
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In this work, a meteorite sample recovered in Morocco is characterized by detailed petrographic observations in transmitted and reflected light optical microscopy and by using XRD and SEM and it is tentatively classified. VIS/NIR spectral analysis of the same meteorite in a previous study suggested that it is seemingly related to the HAMLET meteorite, which was classified as LL4 chondrite. From the obtained results in the refinement of the analysis of the present study, this meteorite is classified as L4 to L5 chondrite. Composition maps across selected chondrules and in the matrix are presented.
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Ruda, Natalia. "WORD-FORMING TYPES OF ROCKS AND MINERALS NAMES IN UKRAINIAN PETROLOGY." Bulletin of Taras Shevchenko National University of Kyiv. Literary Studies. Linguistics. Folklore Studies, no. 31 (2022): 66–69. http://dx.doi.org/10.17721/1728-2659.2022.31.13.
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Dynamic development of petrology leads to the intensification of the processes of terms formation. The need to organize the system of rocks and minerals names in the Ukrainian language in accordance with international standards, to unify and to standardize it is becoming increasingly important. A number of problems related to the functioning and development of Ukrainian (and international) petrological terminology, including the transcription of international names in the national language, constant changes in spelling, the existence of doublet terminological elements, synonymy of terms, etc. require the attention of not only naturalists but also linguists. The article considers the issues of petrological terms formation in the Ukrainian language. Attention is focused on the description and analysis of the main word-forming types of rocks and minerals names. The main problems of rocks and minerals names formation in modern Ukrainian petrology are highlighted. It was found that in modern petrology occurs an extremely branched paradigm of means, types and models of rocks and minerals names formation, which, on the one hand, helps to create the most appropriate name, but on the other hand, causes the emergence of large number of synonyms. It is determined that the terminological derivation in Ukrainian petrology, as well as in international, is based on terminological elements of Greek-Latin origin, to use them properly petrologist needs to know ancient Greek and Latin. The most productive were proved to be suffixal word-forming types; the main prefixal and compositional types were also analyzed. Despite the high productivity of suffixal types, the largest number of irrational, scientifically uninformative names is created through the use of suffixes, while prefixation and composition prevail in the word formation of rational nomenclature.
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Berezhnoy, A. A., N. Hasebe, M. Kobayashi, G. G. Michael, O. Okudaira, and N. Yamashita. "A three end-member model for petrologic analysis of lunar prospector gamma-ray spectrometer data." Planetary and Space Science 53, no. 11 (September 2005): 1097–108. http://dx.doi.org/10.1016/j.pss.2005.02.006.
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Peng, Yan Dong, and Zhi Bin Zhang. "Geochemical Characteristics and Analysis of Tectonic Setting of Hannuoba Basalts from Chifeng Region, Inner Mongolia." Advanced Materials Research 734-737 (August 2013): 340–43. http://dx.doi.org/10.4028/www.scientific.net/amr.734-737.340.
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The Hannuoba basalts from Chifeng region, Inner Mongolia, are continental flood basalt, produced by fissure-t type volcanism in the Miocene. The basalts chemically belong to the tholeiitic series. On the whole, the petrologic compositions are homogeneous. The basalts is characterized by Al2O3 = 11.5%~13.0%, Na2O> K2O and TiO2=1.93~3.29%, chemically belong to the calc-alkaline series with low K2O, which are the agpaitic type; The total amounts of REE of Hannuoba basalts are lower and rich in LREE. There is a weak Eu negative anomaly and weak Ce negative anomaly. The basalts are obviously enriched in incompatible elements (K, Rb, Sr, Zr, Ba, LREE etc.), and depleted in high field-strength element (U,HREE) as well as compatible elements (Co, Ni, Cr etc.).Comprehensive studies have shown that Hannuoba basalts erupted in a stable setting within continental plate and controlled by deep fracture crossed mantle, belonging to continental rift basalt.
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Hughes, Alexandra T., Brian D. Smerdon, and Daniel S. Alessi. "Hydraulic properties of the Paskapoo Formation in west-central Alberta." Canadian Journal of Earth Sciences 54, no. 8 (August 2017): 883–92. http://dx.doi.org/10.1139/cjes-2016-0164.
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In an effort to better understand the hydraulic properties of the Paskapoo Formation, hydraulic conductivity and porosity were evaluated for a region in west-central Alberta. Whereas previous studies have focused mainly on sandstone units in the lower portion of the Paskapoo Formation, in southern and central parts of the province, this study focuses on the middle to upper portions. Hydraulic conductivity values were determined by air permeametry for seven drill cores from the area between Hinton and Fox Creek, Alberta. Thin-section petrology and porosity analyses using photomicrographs were also conducted for three of the seven drill cores. Results confirm previous findings that the Paskapoo Formation has heterogeneous hydraulic properties, with horizontal hydraulic conductivity values ranging from 10−10 to 10−5 m/s (determined by air permeametry) and porosity values ranging from 0.02% to 15.3%. The first measurements for the upper sandstone units are provided (1.1 × 10−9 – 2.6 × 10−5 m/s and 0.08%–15.3%) and numerous measurements of the middle siltstone–mudstone unit (1.1 × 10−10 – 4.9 × 10−8 m/s and 0.02%–1.8%) for the northwestern portion of the Paskapoo Formation. Qualitative petrologic analysis suggests that the degree of cementation, rather than grain size, is the dominant control on the hydraulic properties of this portion of the formation. This study determined primary hydraulic properties for both the highly conductive units often considered as aquifers and the low-conductivity units considered as aquitards or confining layers. When combined with previous findings, this study helps expand the understanding of the Paskapoo Formation and provides critical data for assessing groundwater resources.
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Achyuthan, Hema. "Petrologic analysis and geochemistry of the Late Neogene-Early Quaternary hardpan calcretes of Western Rajasthan, India." Quaternary International 106-107 (January 2003): 3–10. http://dx.doi.org/10.1016/s1040-6182(02)00158-1.
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Cecchi, Vanni, and Stefano Caporali. "Petrologic and Minerochemical Trends of Acapulcoites, Winonaites and Lodranites: New Evidence from Image Analysis and EMPA Investigations." Geosciences 5, no. 3 (July 2, 2015): 222–42. http://dx.doi.org/10.3390/geosciences5030222.
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Zanoni, Davide, and Maria Iole Spalla. "The Variscan evolution in the basement cobbles of the Permian Ponteranica Formation by microstructural and petrologic analysis." Italian Journal of Geosciences 137, no. 2 (June 2018): 254–71. http://dx.doi.org/10.3301/ijg.2018.12.
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Sepahi, Ali Asghar, Seyedeh Razieh Jafari, Yasuhito Osanai, Hossein Shahbazi, and Mohssen Moazzen. "Age, petrologic significance and provenance analysis of the Hamedan low-pressure migmatites; Sanandaj-Sirjan Zone, west Iran." International Geology Review 61, no. 12 (September 10, 2018): 1446–61. http://dx.doi.org/10.1080/00206814.2018.1517392.
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Vakanjac, Boris, Ivana Jelic, Milena Rikalovic, Vesna Ristic-Vakanjac, Dusan Nikezic, Zorana Naunovic, and Slavko Dimovic. "Investigation of accessory elements of representative petrologic radioactivity carriers at Stara Planina, Serbia." Nuclear Technology and Radiation Protection 34, no. 4 (2019): 384–91. http://dx.doi.org/10.2298/ntrp190709039v.
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The present study deals with the abundance of the most common accessory elements of radioactivity carriers on the Stara Planina mountain at four defined locations. All investigated locations have increased radioactivity, greater than 200 cps, up to 1250 cps. In all examined samples the following elements were detected and their concentrations were determined: Zr, Rb, W, Mo, Sn, Zn, Cu, As, Sb, Ba, Ni, Cr, V, and Ti. The analysis showed that depending on the sample, elevated concentrations of all detected elements except titanium were found. As all localities containing the listed detected elements are located near watercourses, all the present elements, and in particular, those with elevated concentrations can be relatively easily transferred to the environment by water action. Likewise, there is the possibility of eolic erosion from the investigated deposits and tailing dams whereby these chemical elements and/or radionuclides would be distributed to areas away from the primary sources of natural radioactivity. These have a high risk of spreading and therefore have harmful or radioecological effects on the environment. The study indicated a need for adequate monitoring, and risk assessment of the examined locations, which could prevent the distribution of these elements further into the environment. [Projects of the Serbian Ministry of Education, Science and Technological Development, Grant no. III 43009 and Grant no.
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Kondor, Henrietta, and Tivadar M Tóth. "Contrasting metamorphic and post-metamorphic evolutions within the Algyő basement high (Tisza Mega-unit, SE Hungary). Consequences for structural history." Central European Geology 64, no. 2 (May 29, 2021): 91–112. http://dx.doi.org/10.1556/24.2021.00004.
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AbstractThe Algyő High (AH) is an elevated crystalline block in southeastern Hungary covered by thick Neogene sediments. Although productive hydrocarbon reservoirs are found in these Neogene sequences, numerous fractured reservoirs also occur in the pre-Neogene basement of the Pannonian Basin. Based on these analogies, the rock body of the AH might also play a key role in fluid storage and migration; however, its structure and therefore the reservoir potential is little known. Based on a comprehensive petrologic study in conjunction with analysis of the spatial position of the major lithologies, the AH is considered to have been assembled from blocks with different petrographic features and metamorphic history. The most common lithologies of garnet-kyanite gneiss and mica schist associated with garnetiferous amphibolite are dominant in the northwestern and southeastern parts of the AH. The first regional amphibolite facies metamorphism of the gneiss and mica schist was overprinted by a contact metamorphic (metasomatic) event during decompression in the stability field of kyanite. Garnet-bearing amphibolite experienced amphibolite facies peak conditions comparable with the host gneiss. Regarding the similarities in petrologic features, the northwestern and southeastern parts of the area represent disaggregated blocks of the same rock body. The central part of the AH area is characterized by an epidote gneiss-dominated block metamorphosed along with a greenschist-facies retrograde pathway as well as a chlorite schist-dominated block formed by greenschist-facies progressive metamorphism. The independent evolution of these two blocks is further confirmed by the presence of a propylitic overprint in the chlorite schists. The different metamorphic blocks of the northwestern, southeastern and central parts of the AH probably became juxtaposed along post-metamorphic normal faults developed due to extensional processes. The supposed brittle structural boundaries between the blocks could have provided hydrocarbon migration pathways from the adjacent over-pressured sub-basins, or could even represent suitable reservoirs.
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Kline, Nicole J., Mark C. Sparrow, and Patrick J. Treado. "Visualizing Molecular Species Within Inorganics: Raman Chemical Imaging of Minerals, Meteorites and Actinides." Microscopy and Microanalysis 3, S2 (August 1997): 859–60. http://dx.doi.org/10.1017/s1431927600011181.
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Raman chemical imaging microscopy is a powerful technique for the characterization of a wide host of materials, including inorganic species. The technique makes use of a liquid crystal tunable filter (LCTF) imaging spectrometer that is integrated within an infinity-corrected optical microscope. The imaging system provides the performance of a dispersive Raman spectrometer at every pixel of the charge-coupled device (CCD) detector used to capture the Raman image.We are currently applying Raman microscopy to the chemical imaging analysis of mineral composition and phase chemistry found in meteorites and terrestrial minerals. Determination of the chemical composition and structure of mineral components is often useful in developing an understanding of the petrologic process that formed the minerals, including those minerals that have been exposed to water. This is of particular interest in light of recent promising evidence of past life in Martian meteorites.
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Delaney, Colleen M., Shawna Couplin, John A. Lawrence, Kathleen M. Marsaglia, and Karen L. Savage. "A Preliminary Petrologic and Provenance Analysis of Groundstone Artifacts from the Northern Channel Islands and Coastal Southern Alta California." California Archaeology 13, no. 2 (July 3, 2021): 227–65. http://dx.doi.org/10.1080/1947461x.2021.1997516.
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Cody, George D., Conel M. O'D Alexander, A. L. David Kilcoyne, and Hikaru Yabuta. "Unraveling the chemical history of the Solar System as recorded in extraterrestrial organic matter." Proceedings of the International Astronomical Union 4, S251 (February 2008): 277–84. http://dx.doi.org/10.1017/s1743921308021741.
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AbstractWe have initiated an extensive program of molecular analysis of extraterrestrial organic matter isolated from a broad range of meteorites (spanning multiple classes, groups, and petrologic types), including recent molecular spectroscopic analyses of the organic matter in the Comet 81P/Wild 2 samples. The results of these analyses clearly reveal the signature of multiple reaction pathways that transformed extraterrestrial organic matter away from its primitive roots. The most significant molecular transformation occurred in the post-accretionary phase of the parent body. However, each of the various chemical transformation trajectories point unambiguously back to a common primitive origin. Applying a wide range of spectroscopic techniques we find that the primitive organic precursor is striking in its chemical complexity exhibiting a broad array of oxygen- and nitrogen-bearing functional groups. The π-bonded carbon exists as predominately highly substituted single ring aromatics, there exists no evidence for abundant, large, polycyclic aromatic hydrocarbons (PAHs). We find that the molecular structure of primitive extraterrestrial organics is consistent with synthesis from small reactive molecules, e. g. formaldehyde, whose random condensation and subsequent rearrangement chemistry at low temperatures leads to a highly cross-linked macromolecule.
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Muslih, Khamis D. "Identifying the Climatic Conditions in Iraq by Tracking Down Cooling Events in the North Atlantic Ocean in the Period 3000–0 BC." Miscellanea Geographica 18, no. 3 (September 30, 2014): 40–46. http://dx.doi.org/10.2478/mgrsd-2014-0016.
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Abstract North Atlantic Oscillation (NAO), monthly averages of precipitation in the Baghdad station, and petrologic tracer proxy data for ocean properties in the North Atlantic (NA) have been used in an attempt to identify climatic conditions in Iraq during the study period. The study showed that contemporary changes in precipitation in Iraq are associated with NAO, as a negative relationship is found between them. Moreover, the study found that there is a strong negative correlation between NAOI and SST in NA, where drift ice indices explain between 33–36% of the NAOI variability. The prolonged of cold Holocene periods led to a radical oceanography and atmospheric changes in the NA and the Mediterranean Sea, effectively contributing to the prevalence of cold and drought in the EM, including Iraq. The analysis revealed as many as four intervals of significant cool drought phases prevailing over Iraq during the periods 2650–2500, 2200– 1900,1300–1200 and 1000–850 BC.
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Kodolányi, János, Peter Hoppe, Christian Vollmer, Jasper Berndt, and Maren Müller. "Iron-60 in the Early Solar System Revisited: Insights from In Situ Isotope Analysis of Chondritic Troilite." Astrophysical Journal 929, no. 1 (April 1, 2022): 107. http://dx.doi.org/10.3847/1538-4357/ac5910.
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Abstract We measured the nickel isotope composition of troilites from chondritic meteorites using the NanoSIMS to put constraints on the abundance of iron-60 in the early solar system. The troilites were selected from petrologic type 3 ordinary and carbonaceous chondrites. Based on petrographic observations and mineral chemistry, the troilites targeted for isotope analysis crystallized from melts, most likely in a nebular setting. Our isotope analyses did not reveal any significant correlation between nickel-60 enrichments and Fe/Ni ratios, either in the entire set of troilite grains or in individual troilites. The average inferred initial 60Fe/56Fe ratio of the studied troilites (i.e., the 60Fe/56Fe ratio calculated for the entire troilite population) is 1.05 (±1.48) ×10−8. This value is very similar to those estimated in the past for Semarkona chondrules, angrites, as well as diogenites and eucrites, based on the isotope analyses of bulk samples (109–108), but about two orders of magnitude smaller than the average initial 60Fe/56Fe ratios inferred previously for Semarkona troilites and many chondrules from ordinary and carbonaceous chondrites (107–106) using in situ analysis techniques. Based on petrographic evidence, and the generally unequilibrated nature of our samples, as well as on the timing of chondrule formation and planetary evolution, the lack of discernible signs of in situ iron-60 decay in the studied troilites is probably unrelated to metamorphic re-equilibration, and it is also not the result of a late formation of the troilites. We suggest that the highest inferred initial 60Fe/56Fe ratios reported in the literature are probably inaccurate.
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Kammer, Thomas W., and William I. Ausich. "Aerosol suspension feeding and current velocities: distributional controls for late Osagean crinoids." Paleobiology 13, no. 4 (1987): 379–95. http://dx.doi.org/10.1017/s009483730000899x.
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Distributional patterns of late Osagean (Mississippian) crinoids from the east-central United States are examined using multivariate analysis of crinoid species diversity and species abundance data. We confirm previous hypotheses that three well-defined crinoid associations existed during the late Osagean. These associations were dominated, respectively, by 1) monobathrid camerates preserved in carbonate packstones; 2) poteriocrine inadunates in higher-energy siltstones and sandstones; and 3) disparid inadunates, cyathocrine inadunates, and flexibles in mudstones where neither monobathrids nor poteriocrines dominated. In conjunction with petrologic data on the enclosing sediments, the analyses suggest that these associations occurred along a spectrum of increasing current velocity at the seafloor. Camerates, poteriocrine inadunates, and flexibles are interpreted to display preferences for specific environmental conditions, whereas disparid and cyathocrine inadunates are inferred to be environmental generalists.The different environmental distributions of the major crinoid groups are interpreted to be a function of the mode or modes of aerosol filtration feeding used by each group. This inference is possible through functional morphologic and morphometric studies of crinoid arms, because the skeletal elements of the arms, which are commonly preserved, are directly involved in feeding.
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Heinemeier, Jan, Åsa Ringbom, Alf Lindroos, and Árný E. Sveinbjörnsdóttir. "Successful AMS 14C Dating of Non-Hydraulic Lime Mortars from the Medieval Churches of the Åland Islands, Finland." Radiocarbon 52, no. 1 (2010): 171–204. http://dx.doi.org/10.1017/s0033822200045124.
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Fifteen years of research on accelerator mass spectrometry (AMS) radiocarbon dating of non-hydraulic mortar has now led to the establishment of a chronology for the medieval stone churches of the Åland Islands (Finland), where no contemporary written records could shed light on the first building phases. In contrast to other material for dating, well-preserved mortar is abundantly available from every building stage.We have gathered experience from AMS dating of 150 Åland mortar samples. Approximately half of them have age control from dendrochronology or from 14C analysis of wooden fragments in direct contact with the mortar. Of the samples with age control, 95% of the results agree with the age of the wood. The age control from dendrochronology, petrologic microscopy, chemical testing of the mortars, and mathematical modeling of their behavior during dissolution in acid have helped us to define criteria of reliability to interpret the 14C results when mortar dating is the only possibility to constrain the buildings in time. With these criteria, 80% of all samples reached conclusive results, and we have thus far been able to establish the chronology of 12 out of the 14 churches and chapels, while 2 still require complementary analyses.
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Franchini, Marta, Agnes Impiccini, David Lentz, Francisco Javier Ríos, Sol O'Leary, Josefina Pons, and Abel Isidoro Schalamuk. "Porphyry to epithermal transition in the Agua Rica polymetallic deposit, Catamarca, Argentina: An integrated petrologic analysis of ore and alteration parageneses." Ore Geology Reviews 41, no. 1 (October 2011): 49–74. http://dx.doi.org/10.1016/j.oregeorev.2011.06.010.
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Ban, Masao, Konosuke Kawashima, Kae Tsunematsu, Takumi Imura, Kyoko S. Kataoka, and Tohru Yamanoi. "Geologic and Petrologic Characteristics of the Lahar Deposits at the Western Foot of Zao Volcano." Journal of Disaster Research 17, no. 5 (August 1, 2022): 736–44. http://dx.doi.org/10.20965/jdr.2022.p0736.
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The lahars are one of the most hazardous volcanic phenomena causing the third greatest causalities among the volcanic hazards since the 16th century worldwide. Lahars can flow down a long distance and cause tremendous disaster at the foot of volcanoes often beyond the areas of primary volcanic impacts of pyroclastic fall and pyroclastic density currents. Therefore, the research on lahar history of active volcanoes approaching from an analysis of a geological record in distal volcanic regions is significant for lahar hazard risk evaluation. Zao volcano has high risks of future eruptions, because volcanic tremors have been detected since 2013. The presence of a crater lake at the summit area, and steep slopes at the high altitude of Zao indicates high potential energy for future lahars, if triggered by an eruption starting underneath the crater lake. This study firstly reports the existence of lahar deposits at the western foot of Zao and discusses the depositional features and the origin of these as well as the lahar hazard risk at this volcano. The lahar deposits were exposed during the archaeological excavation of the Fujiki ruin, western foot of the Zao volcano. Two major lahar units, L1 and L2, were recognized. Based on the 14C dating and stratigraphic relationships, the ages of units L1 and L2 were estimated to be <ca. 4.0 and ca. 4.6 cal ka, respectively. The lithology, granulometry, and componentry features of the lahar deposits revealed the depositional features and the source materials. The upper part of L1 (L1-1) unit and lower part of L2 (L2-2) unit were deposited from a hyperconcentrated flow, whereas, the lower part of L1 (L1-2) unit and upper part of L2 (L2-1) unit were formed by a debris flow. The sources of both units were phreatomagmatic eruption products that may have erupted shortly before the lahar events. This implies that these eruptions were the most plausible trigger for the lahars. These results suggest that lahar risk will increase especially after the phreatomagmatic eruptions as well as phreatic eruptions, even in the western foot of this volcano.
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Ambrosio, Francesco Antonio. "A new statistical approach to the geochemical systematics of Italian alkaline igneous rocks." Open Geosciences 12, no. 1 (May 17, 2020): 133–47. http://dx.doi.org/10.1515/geo-2020-0013.
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AbstractThe ultra-alkaline rocks have exotic features that frustrated many attempts to group them in a single classification diagram. A consistent classification would be very useful to define a possible consanguinity, an argument that feed a living debate. This paper investigates the petrologic characteristics of the Cenozoic Italian ultra-alkaline rock-suite using -Rank Entropy Anentropy (RHA) and Principal Component Analysis (PCA)-. The RHA formula is the succession of component’s symbols arranged according to the diminishing of their elemental content in the analysis (whole rock composition). Other two parameters considered are an expression of the anentropy and entropy of the system. The PCA allows the definition of new latent variables based on geochemical compositions through linear combinations of the major oxides. Using both statistical methods was possible to create discrete groups of rock-types, associated by genetic relationship. The groups plotted in the Mg-Ca-Al ternary diagram depicts two main evolutionary arrays. We interpret the chemical variance in term of a general magmatic processes based on immiscibility and crystal fractionation. A comparison with similar association worldwide give a more general prospective to the magmato-tectonic assignment of these rocks, which is highly controversial in Italy.
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Fujita, Eisuke, Masato Iguchi, Yuichi Morita, Setsuya Nakada, Mitsuhiro Nakagawa, and Yuki Suzuki. "Special Issue on Future Volcano Research in Japan: Integrated Program for Next-Generation Volcano Research." Journal of Disaster Research 17, no. 5 (August 1, 2022): 585–86. http://dx.doi.org/10.20965/jdr.2022.p0585.
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Since Japan has 111 active volcanoes, we living there need to be prepared for the volcanic disasters that we will likely encounter in our lifetime. The Integrated Program for Next Generation Volcano Research and Human Resource Development (INeVRH), a research project of the Ministry of Education, Culture, Sports, Science and Technology (MEXT), started in 2016 and is now in its 7th year. It is approaching its final stage will be ready to make proposals that will improve our knowledge from both scientific and practical points of view. In theme A, the Japan Volcanic Data Network (JVDN) system started its function as a volcanic research platform, providing the observation and analysis data of many universities, governmental agencies, and institutes. The JVDN system promotes collaborative, multidisciplinary study. In theme B, many strategic observation techniques now deployed have revealed the characteristics of volcanoes in detail. For example, a dense seismic and magnetic survey has clarified the fine structure of the hydrothermal system beneath volcanoes, providing information that can be used to evaluate their phreatic eruption potential. In addition, brand-new volcanic gas observation techniques using drones now obtain in-situ information effectively. Theme C has obtained geologic and petrologic findings at many volcanoes and has come to the stage in which systematic compilation of this database would be useful to comparative studies of many volcanoes. These findings are also used in numerical simulations that combine geologic, petrologic, and geophysical formulations to produce more comprehensive models used to interpret volcanic activity. Theme D focuses on the development of practical technologies for volcanic disaster mitigation, mainly related to volcanic ash. A scheme for the quick detection and evaluation of volcanic ash is proposed through observation and numerical simulation, and an experiment is performed to reveal the thickness threshold of volcanic ash deposits on air-conditioners. This special issue reports on some up-to-date topics that could become the basis of dynamic and effective links between themes A, B, C, and D, which may serve as a base and direction for discussions that summarize and conclude this 10-year project.
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Hasria, Masri, Suryawan Asfar, Arisona, Ali Okto, La Ode Restele, La Ode Ngkoimani, and Rika Yustika. "Characteristics of Chromite Deposits at North Kabaena District, Bombana Regency, Southeast Sulawesi Province, Indonesia." Journal of Geoscience, Engineering, Environment, and Technology 6, no. 2 (June 8, 2021): 94–98. http://dx.doi.org/10.25299/jgeet.2021.6.2.6424.
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The study area is located in North Kabaena District, Bombana Regency, Southeast Sulawesi. This paper is aimed to describe characacristics of chromite deposits. This study is conducted in three stages, three stages including desk study, field work and laboratory analysis. Desk study mainly covers literature reviews. Field work includes mapping of surface geology and sampling of representative rocks types. Laboratory analysis includes the petrologic observation of handspecimen samples, petrographic analysis of the thin section and ore microscopy for polished section. The results of petrographic analysis show that olivine minerals are generally replaced by minerals orthopyroxene and has been alterated by lizardite type serpentine veins with a fractured structure. The mineral olivine is also replaced by the mineral chrysotile as a secondary mineral with a fibrous structure. Based on ore microscopy analysis show that chromite has generally experienced a lateritification process and has been replaced by magnetite, hematite and geotite minerals. Chromite has experience process of weathering and alteration from its source rock caused by tectonics that occurred in the study area. The results shows that the characteristics of chromite deposits in North Kabaena District Chromite deposits has generally encountered in peridotite rock which have a grain size of 0.3-20 cm. Furthermore, chromite deposits in the study area are also encountered in podiform deposits, distributed locally and shows podiform to tubular shape with the dimensions of 30-60cm.
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LEDEVIN, MORGANE, NICHOLAS ARNDT, MARK R. COOPER, GARTH EARLS, PAUL LYLE, CHARLES AUBOURG, and ERIC LEWIN. "Intrusion history of the Portrush Sill, County Antrim, Northern Ireland: evidence for rapid emplacement and high-temperature contact metamorphism." Geological Magazine 149, no. 1 (September 19, 2011): 67–79. http://dx.doi.org/10.1017/s0016756811000537.
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AbstractThe gabbroic Portrush Sill in Northern Ireland, part of the North Atlantic Igneous Province, intruded Lower Jurassic mudstones and siltstones about 55 Ma ago. We used petrologic observations and geochemical analyses to study how the sill interacted with the sedimentary rocks. Field relationships show that an Upper Sill and numerous associated Minor Intrusions were emplaced in the sedimentary host rocks before intrusion of the Main Sill, some 10 m above its upper contact. Geochemical analyses reveal two magma contamination processes: Nb and Ta anomalies, coupled with incompatible element enrichment, record contamination by deep crustal rocks, whereas Li, Pb and Ba anomalies reveal a superficial contamination through fluid circulation at the contact between magmatic and sedimentary rocks. Analysis of mineral assemblages and geochemical data from the contact aureole demonstrate uniform metamorphic conditions between the two main intrusions and an absence of a thermal gradient. The identification of pyrrhotite by magnetization analyses and of orthopyroxene by microprobe analyses indicates very high temperatures, up to 660°C. Thermal modelling explains these temperatures as the coupled effects of the Main Sill and the earlier intruded Upper Sill and Minor Intrusions. Even though the chemical composition of the Main Sill suggests another type of parental liquid, all three units were emplaced in a very short time, certainly less than five years.
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Reynolds, R. L., M. Webring, V. J. S. Grauch, and M. Tuttle. "Magnetic forward models of Cement oil field, Oklahoma, based on rock magnetic, geochemical, and petrologic constraints." GEOPHYSICS 55, no. 3 (March 1990): 344–53. http://dx.doi.org/10.1190/1.1442842.
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Magnetic forward models of the Cement oil field, Oklahoma, were generated to assess the possibility that ferrimagnetic pyrrhotite related to hydrocarbon seepage in the upper 1 km of Permian strata contributes to aeromagnetic anomalies at Cement. Six bodies having different magnetizations were constructed for the magnetic models, based on geology and on petrologic and geochemical results, supplemented by rock magnetic measurements of shallow‐core and outcrop samples. The column of rock through which hydrocarbons have passed is divided into three sulfide zones on the basis of pyrrhotite content, and the column is capped by a 30 m thick zone that contains ferric oxide minerals formed mainly from oxidized pyrite. Red beds unaffected by sulfidization, as well as a zone of rock depleted in hematite but lacking sulfide, surround sulfidic zones. The synthetic magnetic profiles are controlled mainly by pyrrhotite‐bearing strata at depths of 200–500 m. The magnetizations of these bodies are calculated from: (1) petrographic estimates of pyrrhotite content relative to pyrite; (2) content of sulfide sulfur determined from chemical analysis; and (3) values for the magnetic susceptibility of monoclinic pyrrhotite. Total magnetizations of the bodies of highest pyrrhotite content range from about [Formula: see text] to [Formula: see text] in the present field direction and yield magnetic anomalies (at 120 m altitude) having amplitudes of less than 1 nT to ∼6 to 7 nT, respectively. Such amplitudes are much lower than those (as high as 60 nT) reported from the original total‐field survey over the Cement field. Numerous assumptions were made in the generation of the models, and thus the results neither prove nor disprove the existence of aeromagnetic anomalies related to hydrocarbon seepage at Cement. Nevertheless, the results suggest that pyrrhotite, formed via hydrocarbon reactions and within a range of concentrations estimated at Cement, is capable of causing magnetic anomalies.
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Yang, Leilei, Linjiao Yu, Donghua Chen, Keyu Liu, Peng Yang, and Xinwei Li. "Effects of Dolomitization on Porosity during Various Sedimentation-Diagenesis Processes in Carbonate Reservoirs." Minerals 10, no. 6 (June 25, 2020): 574. http://dx.doi.org/10.3390/min10060574.
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Carbonate reservoirs, especially dolomite reservoirs, contain large reserves of oil and gas. The complex diagenesis is quite challenging to document the dolomite reservoirs formation and evolution mechanism. Porosity development and evolution in dolomite reservoirs primarily reflect the comprehensive effect of mineral dissolution/precipitation during dolomitization. In this study, multicomponent multiphase flow and solute transport simulation was employed to investigate dolomitization in the deep carbonate strata of the Tarim Basin, Northwest China, where active exploration is currently under way. One- and two-dimensional numerical models with various temperatures, fluid compositions and hydrodynamic characteristics were established to quantificationally study dolomitization and its effect on porosity. After determining the main control factors, detailed petrologic characteristics in the studied area were also analyzed to establish four corresponding diagenetic numerical models under different sedimentary environments. These models enabled a systematic analysis of mineral dissolution/precipitation and a quantitative recovery of porosity evolution during various sedimentation-diagenesis processes. The results allowed for a quantitative evaluation and prediction of reservoir porosity, which would provide a basis for further oil and gas exploration in deep carbonate reservoirs.
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Yager, Douglas B., Albert H. Hofstra, Katheryn Fifarek, and Ank Webbers. "Development of an igneous rock database with geologic functions: Application to Neogene bimodal igneous rocks and mineral resources in the Great Basin." Geosphere 6, no. 5 (October 1, 2010): 691–730. http://dx.doi.org/10.1130/ges00516.1.
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Abstract Geologists routinely use sample data (descriptive, qualitative, quantitative) to characterize a hierarchy of larger geologic features that each have their own independent attributes, use physical relationships between geologic features to establish their relative ages, combine this information with dated features to understand evolutionary histories of study areas at various scales, and produce maps to display such information in space and time relative to other features of interest. This paper demonstrates how we integrated such routine geologic functions into an existing igneous rock relational database designed to store, organize, update, query, and retrieve sample data that have well-defined locations. The resulting igneous rock database is utilized to capture information on Neogene bimodal igneous rocks in northern Nevada and the eastern Great Basin Province. The database is a useful tool that facilitates queries to generate geographical information system displays and petrologic plots that elucidate the time-space-composition relationships of volcanic centers to one another and to geophysical anomalies, structural features, and mineral deposits. Database information is parsed into the following data tables: physical hierarchy of scale, absolute and relative age, chemistry, paleomagnetic, rock mode, image, cross section, X-ray diffraction, and igneous-related structure. Information is organized in a telescoping geologic hierarchy schema: igneous province, volcanic field, volcanic system or caldera, extrusive flow or intrusion, sample, and various subsamples. Absolute radiometric age determinations on samples from geologic features and expert interpretations of relative age relationships between different features may be captured and used together to constrain the ages of undated features. Such age information is linked to features of various scales in the hierarchy. Common attributes that are shared between the relational database and geographic information system (GIS) features include feature-identification or sample-identification, and they permit linking of geographic entities and tabular data for query, analysis, and display in GIS or derivative tables. Relational database keys merge analytical, map, and image data across this geologic hierarchy-age-location schema to facilitate queries that address geologic problems. Data acquired at the sample scale of observation is linked to increasingly larger features that have their own independent attributes using GIS. This schema enables users to retrieve information on one or more hierarchical features for input into external software for various GIS, statistical, petrologic, and other display, analysis, or comparison purposes. Fundamental interpretations resulting from such analyses or displays, e.g., rock classification, may be used to populate additional fields in the database. The database is designed for flexibility and can accommodate information resulting from both detailed and reconnaissance studies. The geologic functions that were developed and that we added to an existing igneous rock database (Lehnert et al., 2000) for this study have wide applicability and could readily be integrated into other geoscience databases.
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Carramal, Nívea G., Daniel M. Oliveira, Alessandra S. M. Cacela, Matheus A. A. Cuglieri, Natasha P. Rocha, Samuel M. Viana, Sérgio L. V. Toledo, Saulo Pedrinha, and Luiz F. de Ros. "Paleoenvironmental insights from the deposition and diagenesis of Aptian pre-salt magnesium silicates from the Lula Field, Santos Basin, Brazil." Journal of Sedimentary Research 92, no. 1 (January 11, 2022): 12–31. http://dx.doi.org/10.2110/jsr.2020.139.
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ABSTRACT Since the discovery of giant Aptian pre-salt reservoirs in Brazilian margin basins, the study of lacustrine carbonates has drawn great attention from the scientific community. Comparatively, minor attention was given to the characterization and genesis of the Mg-silicates (e.g., stevensite, kerolite) which are commonly associated with these carbonates. A systematic petrological study was performed in the Aptian Barra Velha Formation (BVF) within distinct structural compartments of the giant Lula Field in the Santos Basin, in order to recognize the patterns of primary formation and diagenetic alteration of these Mg-silicates. Mg-silicates occur as peloids, ooids, intraclasts, and fine-grained laminated deposits, either mixed in variable proportions with other particles, such as carbonate bioclasts and volcanic rock fragments, or constituting specific intrabasinal deposits. In the BVF interval, clay peloids and laminated deposits are associated with spherulitic and fascicular calcite aggregates, as substrate and hosts for these precipitates. Ooids are interpreted as formed at the sediment–water interface by the nucleation of concentric envelopes on the surface of particles (heterogeneous nucleation), through repeated rolling under gentle wave and current action. Laminated deposits, interpreted as precipitated directly from the water column (homogeneous nucleation) in highly supersaturated and low-hydrodynamic-energy environments, constitute extensive deposits in the BVF. Peloids were probably formed in intermediate energy conditions. Some ooidal arenites show porosity from the dehydration and contraction, and/or the dissolution of ooids. In some rocks, these pores are filled with fibrous calcite, while the remaining Mg-silicates are replaced by dolomite, calcite, or silica. A similar diagenetic pattern occurs in the laminated deposits, where magnesite and dolomite fill shrinkage pores formed along their characteristic wavy laminae. Owing to their elevated solubility, most of the Mg-silicates were dissolved, or intensely replaced by calcite, dolomite, or silica. The detailed petrologic analysis indicates that the original volumes of Mg-silicates were substantially larger, and that their deposition was widespread in the basin, including on structurally high areas. The types and intensity of diagenetic alteration of the Mg-silicate deposits are distinct for each structural compartment, being more intense towards the highs and closer to the overlying evaporites, which imposed a strong influence on reservoir quality.
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Toscano, Marguerite A., Juan L. Gonzalez, and Kevin R. T. Whelan. "Calibrated density profiles of Caribbean mangrove peat sequences from computed tomography for assessment of peat preservation, compaction, and impacts on sea-level reconstructions." Quaternary Research 89, no. 1 (January 2018): 201–22. http://dx.doi.org/10.1017/qua.2017.101.
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AbstractOceanic mangroves accumulate peat with sea-level rise without terrestrial sediment inputs, but fossil peat’s elevation as a tide-range limited sea-level indicator is assumed to be affected by compaction. Despite assumption of decomposition, compression, and dewatering, pure Rhizophora mangle peat appears coarse, water-saturated, and loose even at depth. Calibrated peat densities from computed tomography (CT) and petrologic analysis allow quantitative assessment of compaction in continuous peats from Florida (6 m thick), Belize (12 m thick), and Panama (3.5 m thick). Pure peat exhibits voids at all depths and >80% water contents. CT density does not increase with depth; bulk densities are low, minimally variable, and trend-free. Higher CT-density intervals coincide with compositional changes (sediment, coral). CT of peat buried under sediment shows a shift to higher densities. CT of air-dried continuous peat shows uncompressed fine and coarse roots and voids, with negative densities indicative of air in place of interstitial water. Peat’s high water content and hydraulic conductivity prevent dewatering and compaction, hypothetically maintaining original sea-level indicative elevations at intermediate depths. Non-compacted, sediment-free, offshore peats can provide a continuous proxy for reconstructing the record of sea-level rise at any site, if depositional, disturbance, and geochemical and biotic processes affecting 14C ages are also assessed.
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Wilson, Alexander M., and James K. Russell. "Lillooet Glacier basalts, southwestern British Columbia, Canada: products of Quaternary glaciovolcanism." Canadian Journal of Earth Sciences 54, no. 6 (June 2017): 639–53. http://dx.doi.org/10.1139/cjes-2016-0201.
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The retreat of Lillooet Glacier (LG) has exposed a succession of pillow basalt and subordinate amounts of breccia and hyaloclastite. The lithofacies and physiographic setting suggest that the deposits have a glaciovolcanic origin and represent a partially dissected basaltic pillow-dominated tindar. Chemically, the LG volcanic rocks are basalt to basaltic andesite, and, as a group, they represent the highest-silica, Quaternary mafic products in the Garibaldi volcanic belt (GVB). Like other northern GVB (alkaline) basalts, they lack the Nb–Ta depletion signature typically associated with subduction-related products. Geochemical and petrologic analysis indicates that the LG basalts are comagmatic and that chemical variations within the suite are consistent with sorting of the observed phenocryst assemblage: olivine + plagioclase. Thermodynamic modeling establishes shallow, crustal, pre-eruptive storage conditions at <2 kbar (1 kbar = 100 MPa; or 7.5 km) and an H2O content of 0.5–1 wt.%. We estimate that the LG basalts were erupted at the peak of, or during the waning stages of, Fraser glaciation (17–13 ka). The eruption produced an englacial lake that was >150 m deep and that appears to have been sustained throughout the entire eruption (i.e., no discernible passage zone). Using hydrostatic constraints, we calculate a minimum overlying paleo-ice thickness of >645 m and a paleo-ice surface elevation of >1895 m above sea level.
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Baldwin, Suzanne L., Jan Schönig, Joseph P. Gonzalez, Hugh Davies, and Hilmar von Eynatten. "Garnet sand reveals rock recycling processes in the youngest exhumed high- and ultrahigh-pressure terrane on Earth." Proceedings of the National Academy of Sciences 118, no. 3 (January 11, 2021): e2017231118. http://dx.doi.org/10.1073/pnas.2017231118.
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Rock recycling within the forearcs of subduction zones involves subduction of sediments and hydrated lithosphere into the upper mantle, exhumation of rocks to the surface, and erosion to form new sediment. The compositions of, and inclusions within detrital minerals revealed by electron microprobe analysis and Raman spectroscopy preserve petrogenetic clues that can be related to transit through the rock cycle. We report the discovery of the ultrahigh-pressure (UHP) indicator mineral coesite as inclusions in detrital garnet from a modern placer deposit in the actively exhuming Late Miocene–Recent high- and ultrahigh-pressure ((U)HP) metamorphic terrane of eastern Papua New Guinea. Garnet compositions indicate the coesite-bearing detrital garnets are sourced from felsic protoliths. Carbonate, graphite, and CO2 inclusions also provide observational constraints for geochemical cycling of carbon and volatiles during subduction. Additional discoveries include polyphase inclusions of metastable polymorphs of SiO2 (cristobalite) and K-feldspar (kokchetavite) that we interpret as rapidly cooled former melt inclusions. Application of elastic thermobarometry on coexisting quartz and zircon inclusions in six detrital garnets indicates elastic equilibration during exhumation at granulite and amphibolite facies conditions. The garnet placer deposit preserves a record of the complete rock cycle, operative on <10-My geologic timescales, including subduction of sedimentary protoliths to UHP conditions, rapid exhumation, surface uplift, and erosion. Detrital garnet geochemistry and inclusion suites from both modern sediments and stratigraphic sections can be used to decipher the petrologic evolution of plate boundary zones and reveal recycling processes throughout Earth’s history.
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Rodas, M., F. J. Luque, J. F. Barrenechea, J. C. Fernández-Caliani, A. Miras, and C. Fernández-Rodríguez. "Graphite occurrences in the low-pressure/high-temperature metamorphic belt of the Sierra de Aracena (southern Iberian Massif)." Mineralogical Magazine 64, no. 5 (October 2000): 801–14. http://dx.doi.org/10.1180/002646100549805.
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AbstractFour distinct associations of graphite have been identified in the low-pressure, high-temperature belt of the Sierra de Aracena (SW Spain). Syngenetic occurrences include: (1) stratiform graphite mineralization within a calc-silicate series; (2) disseminated graphite within a terrigenous sequence; and (3) ‘restitic’ graphite within anatectic tonalites and their enclaves. Epigenetic graphite occurs as (4) veins cross-cutting mafic granulites.Graphite in all types of occurrences is highly crystalline, with the c parameter close to 6.70 Å. Such c values correspond to temperatures of formation of ∼800°C. The thermal properties of graphite are also typical of well-ordered graphite and provide DTA exothermic maxima ranging from 810 to 858°C depending on the mode of occurrence. The differences among the temperatures of formation estimated by graphite geothermometry, the position of the exothermic maximum in the DTA curves, and petrologic geothermometers are discussed in terms of the applicability of graphite geothermometry to granulite-facies rocks. Carbon isotope analysis yields δ13C values in the range from −31.6 to −21.4% for syngenetic graphite of types I, II and III attributable to biogenically-derived carbon. The heavier signatures for graphite in vein occurrences (δ13C= −17.7 to −18.3%) with respect to syngenetic graphites suggest that isotopically heavy carbonic species were incorporated into the metamorphic fluids (probably as a consequence of decarbonation reactions of the calc-silicate rocks) from which graphite precipitated into the veins. These fluids were strongly channelled through structural pathways.
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Tursi, Fabrizio. "The key role of µH2O gradients in deciphering microstructures and mineral assemblages of mylonites: examples from the Calabria polymetamorphic terrane." Mineralogy and Petrology 116, no. 1 (October 20, 2021): 1–14. http://dx.doi.org/10.1007/s00710-021-00766-8.
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AbstractA careful petrologic analysis of mylonites’ mineral assemblages is crucial for a thorough comprehension of the rheologic behaviour of ductile shear zones active during an orogenesis. In this view, understanding the way new minerals form in rocks sheared in a ductile manner and why relict porphyroblasts are preserved in zones where mineral reactions are generally supposed to be deformation-assisted, is essential. To this goal, the role of chemical potential gradients, particularly that of H2O (µH2O), was examined here through phase equilibrium modelling of syn-kinematic mineral assemblages developed in three distinct mylonites from the Calabria polymetamorphic terrane. Results revealed that gradients in chemical potentials have effects on the mineral assemblages of the studied mylonites, and that new syn-kinematic minerals formed in higher-µH2O conditions than the surroundings. In each case study, the banded fabric of the mylonites is related to the fluid availability in the system, with the fluid that was internally generated by the breakdown of OH-bearing minerals. The gradients in µH2O favoured the origin of bands enriched in hydrated minerals alternated with bands where anhydrous minerals were preserved even during exhumation. Thermodynamic modelling highlights that during the prograde stage of metamorphism, high-µH2O was necessary to form new minerals while relict, anhydrous porphyroblasts remained stable in condition of low-µH2O even during exhumation. Hence, the approach used in this contribution is an in-depth investigation of the fluid-present/-deficient conditions that affected mylonites during their activity, and provides a more robust interpretation of their microstructures, finally helping to explain the rheologic behaviour of ductile shear zones.
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Symons, D. T. A., T. E. Smith, K. Kawasaki, and M. J. Walawender. "Paleomagnetism of the mid-Cretaceous gem-bearing pegmatite dikes of San Diego County, California, USA." Canadian Journal of Earth Sciences 46, no. 9 (September 2009): 675–87. http://dx.doi.org/10.1139/e09-035.
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Pegmatite dikes in the Peninsular Ranges batholith of southwestern California have produced spectacular crystals of semiprecious and precious minerals for over a century. Aside from their economic importance, these dikes straddle a major tectonic boundary and were used to test hypotheses related to the timing and development of this composite batholith. Paleomagnetic analysis of 252 specimens from 20 sites (12 and 8 sites in the western and eastern zones of the batholith, respectively, from 11 mines in five dike districts) isolated a stable characteristic remanent magnetization direction at 19 sites. The site mean directions for the western and eastern zones are statistically indistinguishable at 95% confidence, supporting petrologic and geochemical arguments that the dikes of the two zones are coeval and cogenetic. After correction for the Neogene opening of the Gulf of California, the paleopole for all 19 site mean directions is indistinguishable from the 94 Ma reference paleopole for North America and supports hypotheses that (1) the dikes are genetically related to intrusion of the La Posta-type plutons; (2) the batholith was already assembled beside the northwestern coastline of Mexico at 94 Ma; (3) ENE-side-up tilting of fault blocks in the batholith’s western zone ended by ∼94 Ma; and (4) the far-sided and clockwise-rotated discordant paleopoles found commonly in Late Cretaceous and younger sedimentary rocks of the batholith’s region are mostly the result of inclination-flattening of the remanence and (or) remagnetization by fluid flow, creating a secondary remanence, excluding Neogene tectonic rotations.
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Bonamici, Chloë E., and Tyler B. Blum. "Reconsidering initial Pb in titanite in the context of in situ dating." American Mineralogist 105, no. 11 (November 1, 2020): 1672–85. http://dx.doi.org/10.2138/am-2020-7274.
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Abstract In situ U-Pb dating of titanite, which can preserve trace-element records of various petrologic processes but also incorporates significant initial Pb, has proliferated in recent years. The widespread use of titanite data to construct tectonic P-T-t paths warrants careful assessment of the available dating techniques, as well as attention to the assumptions that underpin the U-Pb data analysis. This contribution provides the first direct comparison of the two major analytical methods [SHRIMP (SIMS) and LA-ICP-MS] for in situ U-Pb titanite dating. A set of well-characterized titanite grains from Harrisville, New York, in the Adirondack Mountains were analyzed for U-Th-Pb isotopes along the same cross-grain traverses by Sensitive High Resolution Ion Microprobe (SHRIMP) and LA-ICP-MS. Both LA-ICP-MS and SHRIMP data sets define approximately linear arrays on the Tera-Wasserburg Concordia (semi-total Pb/U) diagram and would commonly be interpreted as representing a single date population with minor scatter. However, previous studies have suggested that Adirondack titanite actually records two regionally well-defined thermal events, ~50–100 m.y. apart. When titanite data arrays are treated in detail, attempts to determine concordia-intercept ages by robust three-dimensional linear regression produce large uncertainties and/or poor fit statistics that suggest that the data are not, in fact, isochronous. Grain-by-grain analysis of U-Pb titanite data shows that different subsets of titanite (determined by additional geochemical and microstructural data) show different patterns of U-Pb data. By comparing predictions for Pb-ingrowth evolution paths in Tera-Wasserburg diagrams with observed data, it is possible to recognize both a change in initial Pb composition and Pb loss in the Adirondack titanite U-Pb data set. This study provides an example of how greater geochronologic detail can be extracted from large in situ U-Pb titanite data sets. Even when precise dates are not recovered, geological processes and events that cause data scatter can be recognized through analysis of U-Pb data patterns using the Tera-Wasserburg diagram.
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Dohnalik, Marek, and Konrad Ziemianin. "Charakterystyka utworów czerwonego spągowca w aspekcie badań rentgenowskiej mikrotomografii komputerowej i mikroskopii optycznej." Nafta-Gaz 76, no. 11 (November 2020): 765–73. http://dx.doi.org/10.18668/ng.2020.11.01.
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The article presents the results of microtomographic and petrographic investigations of Rotliegend sandstones collected from core material from wells located in the area of the Fore-Sudetic Monocline in its central and northern parts and also on the border of the Fore-Sudetic Monocline and the Mogilno - Łódź Synclinorium. Three areas were selected for the study: Czarna Wieś–Parzęczewo (19 samples), Środa Wielkopolska–Kromolice (21 samples) and Siekierki–Miłosław (21 samples). The aim of the petrologic and microtomographic studies was to investigate how the different reservoir properties of sandstones will be reflected in the results of the methods used. Strong differences between samples from the region of Środa Wielkopolska–Kromolice and the other studied areas have been demonstrated. In the case of this area several key factors were noticed: the highest average value of effective porosity; the highest average content of pores belonging to class VII (pore volume subsystem classification); three times higher average value of the CT porosity coefficient and the largest length of the average chord. Also in terms of petrography (composition of grains, cement type) it is a region where major differences, especially compared to the region of Czarna Wieś–Parzęczewo, can be seen. Based on the obtained results, it was possible to rank the examined regions in terms of their reservoir properties – from the worst (Czarna Wieś–Parzęczewo) to the best (Środa Wielkopolska–Kromolice). These conclusions are also confirmed by other petrophysical analyses (eg. mercury porosimetry, permeability analysis). Combination of the obtained microtomographic and petrographic results allowed to obtain a full characterization of the investigated samples – both in terms of the mineralogical composition of grains, as well as the development of the pore space. These data, especially in combination with the results of density and porosity analyses (helium pycnometry and mercury porosimetry), open up a number of possibilities to carry out different types of modeling (porosity, permeability) both on the scale of the sample itself, as well as the scale of a single well or even the whole basin, which is crucial for creating a hydrocarbon exploration strategy.
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Le Pennec, J.-L., G. de Saulieu, P. Samaniego, D. Jaya, and L. Gailler. "A Devastating Plinian Eruption at Tungurahua Volcano Reveals Formative Occupation at ∼1100 cal BC in Central Ecuador." Radiocarbon 55, no. 3 (2013): 1199–214. http://dx.doi.org/10.1017/s0033822200048116.
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Based on archaeological and radiometric constraints, previous studies have divided pre-Columbian times of Ecuador into a succession of cultural periods. The Paleoindian and Preceramic periods encompass the time from the first Amerindian occupation to about 4000 BC. The Formative period extends from ∼4000 to ∼300 BC, while the Regional Development (∼300 BC to ∼AD 700) and Integration periods predate the Columbian period, which starts in AD 1533 in Ecuador. The Formative cultural period is poorly known from earlier studies. Here, we bring the first documentation of Formative age occupation around Tungurahua Volcano, 120 km SW of Quito, and show that local settlements were devastated by a violent eruption around 1100 cal BC. Recent volcanological works combining lithostratigraphic, petrologic, and geochronologic analyses reveal that the steep-sloped Tungurahua edifice suffered a major Late Holocene flank failure. We show that the failure event resulted from a major explosive eruption triggered by massive magma intrusion inside the volcano. Decompression of the magma due to a flank collapse resulted in a violent, high-velocity directed blast explosion, which deposited charcoaland sherd-rich ash layers upon and near the volcano. Our 14C results range from 2225 ± 30 to 5195 ± 45 BP, but most cluster between 2640 ± 45 and 3195 ± 45 BP. A calibration analysis indicates that the event took place at ∼1100 cal BC, in the Formative period. We gathered 38 pottery sherds from 3 localities. The sherds show a diversity of size, shape, color, and ornamentation. Examination of pastes, surface finish, and firing indicates that our material shares many common features from site to site. The material from Tungurahua shares affinities with the Cotocollao tradition, which developed in the Quito region between 1500 and 500 BC, and with the Machalilla tradition (coastal region of Ecuador), with the occurrence of carinated bowls with punctuate decorations at 1500–1000 BC. Our study reveals that the ∼1100 cal BC Plinian eruption of Tungurahua Volcano is among the oldest known volcanic disasters in the Andes.
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Darling, Robert S., Jessica L. Gordon, and Ellis R. Loew. "Microscopic Blue Sapphire in Nelsonite from the Western Adirondack Mountains of New York State, USA." Minerals 9, no. 10 (October 16, 2019): 633. http://dx.doi.org/10.3390/min9100633.
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Microscopic, non-gem quality, grains of blue sapphire (corundum) have been identified in a small (1–2 cm wide), discontinuous, dike of nelsonite hosted by aluminous feldspathic gneiss. The gneiss was excavated during the construction of a hydroelectric plant on the Black River at Port Leyden, NY (western Adirondack Highlands). The sapphire location is 250 m NE of the Port Leyden nelsonite deposit. The small dike may represent a separate intrusion of nelsonite or one sheared from the main nelsonite orebody during Ottawan (circa 1050 Ma) deformation and metamorphism. The sapphires range in size from 0.1 to 2.0 mm, and commonly show parting, pleochroism, and hexagonal oscillatory zoning (from deep blue to clear). Electron microprobe analysis shows comparable levels of Fe in both clear (0.71–0.75 wt. %) and blue (0.38–0.77 wt. %) portions of grains, but clear sections have significantly lower TiO2 levels (0.002–0.011 wt.%) compared to blue sections (0.219–0.470 wt. %). Cr2O3 abundances range from 0.006 to 0.079 wt. % whereas V2O3 abundances range from 0.010 to 0.077 wt. % in blue sapphires. Small amounts of MgO were detected in one of the clear corundum grains (0.013 wt. %) and two of the six blue grains (0.001–0.015 wt. %), but the remaining five grains were below the limit of detection. Ga2O3, however, was detected in five out of six blue-colored grains (0.026–0.097 wt. %) but was below the limits of detection for clear grains. Optical spectroscopic data collected on the blue sapphire grains show broad absorbance in the yellow, orange, and red part of the spectrum (~565–740 nm) consistent with intervalence charge transfer between the next nearest neighbor Fe2+ and Ti4+. A magmatic origin of the sapphire grains is supported by petrologic and trace element data from the blue sapphires, but Cr abundances are inconsistent with this interpretation. Sapphire in a nelsonite host rock represents a new type of occurrence.
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Paul, Rick L., and Michael E. Lipschutz. "Labile Trace Elements in Some Antarctic Carbonaceous Chondrites: Antarctic and Non-Antarctic Meteorite Comparisons." Zeitschrift für Naturforschung A 44, no. 10 (October 1, 1989): 979–87. http://dx.doi.org/10.1515/zna-1989-1010.
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Abstract We report data for Ag, Au, Bi, Cd, Co, Cs, Ga, In, Rb, Sb, Se, Te, TI, U and Zn determined by radiochemical neutron activation analysis in consortium samples of Belgica (B) 7904, Yamato (Y) 82042, Yamato 82162 and Yamato 86720 carbonaceous chondrites. These trace elements cover a wide volatility/mobility range and give unique information on thermal histories of meteorites. The results indicate the unique nature of these carbonaceous chondrites. Y-82042 proves to have the volatile element pattern of a C2 ( ≡CM) chondrite and the petrologic characteristics of a CI (n≡CI) chondrite. These must be primary nebular condensation/accretion features, unaffected by post-accretionary processes. The other three meteorites were thermally metamorphosed in ≧2 parent regions over the 600-700 °C range, at relative temperatures B-7904 < Y-82162< Y-86720. Before heating, B-7904 and Y-86720 had C2-levels of volatile elements: Y-82162 had uniquely high volatile element concentrations, at about CI-levels. The data require a new classification scheme for such chondrites. Belgica 7904 and Y-82162 and -86720 seem to be derived from one or more thermally altered carbonaceous asteroids, and their spectral characteristics should be compared with those of B-, F-, G- or T-asteroids. These results indicate substantial differences in the thermal histories of Antarctic and non-Antarctic CI and C2 chondrite populations. In reviewing all that is known about the Antarctic and non-Antarctic meteorite populations, the overwhelming weight of evidence supports the view that these populations sample different extraterrestrial source materials, differing in thermal histories. It may be that over the extended collecting period of the Antarctic ice sheet, it has sampled a considerably greater proportion of near-Earth asteroids than do current falls.
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Mahan, Kevin H., Michael L. Williams, and Julia A. Baldwin. "Contractional uplift of deep crustal rocks along the Legs Lake shear zone, western Churchill Province, Canadian Shield." Canadian Journal of Earth Sciences 40, no. 8 (August 1, 2003): 1085–110. http://dx.doi.org/10.1139/e03-039.
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The Legs Lake shear zone juxtaposes high-pressure (1.0+ GPa) granulite- and eclogite-facies rocks with low-pressure (~0.5 GPa) amphibolite- to granulite-facies rocks, and thus may represent an important crustal-scale, exhumation-related structure in the western Canadian Shield. Field mapping and structural and petrologic analysis document the deformation and metamorphic history of rocks within and adjacent to the shear zone. At least two important phases of deformation are recorded: (1) early oblique thrusting (D2) that placed high-grade rocks over lower grade rocks, and (2) more discrete and lower grade brittleductile normal faulting (D3) that may represent the later part of the exhumation history. The northwest-dipping shear zone consists of 58 km of mylonite in map view, which bounds the southeast margin of the East Athabasca mylonite triangle. High-pressure granulite-facies metamorphism (~750850 °C, 1.01.2 GPa) occurred in the East Athabasca mylonite triangle at ca. 1900 Ma, prior to D2 juxtaposition with the adjacent low-pressure Hearne domain. Thermobarometry from GrtCrdSilBtQtz metapelites in the Hearne domain suggests peak conditions reached 600700 °C and 0.450.5 GPa, which are interpreted to have occurred late during D2. Published and preliminary UPb isotope dilution - thermal ionization mass spectrometry (ID-TIMS) zircon geochronology and electron microprobe monazite geochronology suggest that deformation in the Legs Lake shear zone coincided with the ca. 18301810 Ma terminal collision in the Trans-Hudson orogeny. Extensional faulting during D3 most likely occurred after ca. 1780 Ma. A multi-stage process of exhumation involving both thrust and normal-sense shearing, may serve as a model for the exhumation of other regionally extensive deep-crustal exposures.
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Koesoemadinata, Adam P., and George A. McMechan. "Correlations between seismic parameters, EM parameters, and petrophysical/petrological properties for sandstone and carbonate at low water saturations." GEOPHYSICS 68, no. 3 (May 2003): 870–83. http://dx.doi.org/10.1190/1.1581039.
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Empirical relations are found between measured petrophysical/petrologic, seismic, and electrical properties of sandstone and carbonate samples by least‐squares fitting at room pressure and ambient saturation. The measured parameters include porosity (φ), fluid permeability (k), clay content (C), grain density (ρg), bulk density (ρb), P‐wave velocity (Vp), electrical conductivity (σ), and dielectric constant (κ). The samples are from reservoir analog sites in the Ferron Sandstone in central Utah and the Ellenburger carbonate in central Texas. Crossplots and regression analysis are done separately for the sandstone and the carbonate samples. For the sandstone samples, predictions with correlation coefficients (R2) greater than 0.75 include ρb from φ, ln k from φ and C, κ from ln k and φ, κ from ρb and C, and κ from ln k. Predictions with 0.65 < R2 < 0.75 include κ from Vp and ρb, κ from Vp and φ, Vp from ln k and C, κ from ln φ, and κ from ρb. In general, σ is difficult to predict, with the best R2(0.48) obtained in a prediction of σ from ln k. Relationships for the carbonate samples are generally less reliable, which is attributed to a complex history of multiple phases of karsting and burial. The largest R2 values obtained are 0.67 for prediction of σ from κ, and 0.36 for prediction of σ from ρg. All the other R2 values are ≤0.19. Both the sandstone and the carbonate data show σ‐φ; relations with negative coefficients, rather than positive as predicted by Archie's law, because of the very low water saturations. In the sandstone, the water connectivity is reduced with increasing grain surface area (with increasing φ and k), so σ decreases. In the carbonate, σ correlates with the degree of dolomitization, and the water content is too low to contribute to σ.
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Miyamoto, Kazuo. "Decarbonizing Technique for Casting Iron to Make Wrought Iron Products in Northern Kyushu during the Yayoi Period." Materials Science Forum 983 (March 2020): 25–30. http://dx.doi.org/10.4028/www.scientific.net/msf.983.25.
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Iron furnaces first appeared in western Japan at the end of the Middle Yayoi period, around the 1st century BC. At the same time, iron tools and weapons started to be produced in western Japan using iron raw materials imported from the continent. We discovered the first ever iron furnace that had been constructed on the surface with a clay wall and bellows at Karakami Site, Iki Island, Nagasaki Prefecture. At this site, flat iron and fragments of casting iron were found along with a large quantity of stone tools related to the site. Given the different structure of the furnace on the surface with the bellows along with the lack of iron slag and cut iron fragments, it is probable that this type of furnace was used for the production of wrought iron by decarbonizing from cast iron. This decarbonizing technique of making wrought iron from cast iron has been successfully demonstrated through experimental archeology. When comparing the forms of flat iron found in northern Kyushu during the Yayoi period, the same forms of flat iron are only found in the Itoshima area or lower Onga River area, but not in the Fukuoka Plains. In addition, pottery from the Itoshima area and lower Onga River area of the Middle Yayoi period is found at Karakami Site, although pottery from the Fukuoka Plains has not been found at this site through petrologic analysis. Therefore, it is believed that flat iron from wrought iron ingots produced by decarbonizing from cast iron in furnaces on the surface was exported from Karakami Site to the Itoshima area or the lower Ongagawa area. On the other hand, there was no trading of wrought iron ingots between Karakami Site of Iki Island and the Na area of the Fukuoka Plains.
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Pankhurst, Matthew J., Jane H. Scarrow, Olivia A. Barbee, James Hickey, Berverly C. Coldwell, Gavyn K. Rollinson, José A. Rodríguez-Losada, et al. "Rapid response petrology for the opening eruptive phase of the 2021 Cumbre Vieja eruption, La Palma, Canary Islands." Volcanica 5, no. 1 (January 10, 2022): 1–10. http://dx.doi.org/10.30909/vol.05.01.0110.
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How and why magmatic systems reactivate and evolve is a critical question for monitoring and hazard mitigation efforts during initial response and ongoing volcanic crisis management. Here we report the first integrated petrological results and interpretation provided to monitoring authorities during the ongoing eruption of Cumbre Vieja, La Palma, Canary Islands, Spain. The first eruptive products comprised simultaneous Strombolian fountain-fed lava flows and tephra fall from near-continuous eruption plumes. From combined field, petrographic and geochemical analyses conducted in the 10 days following sample collection, we infer low percentage mantle melts with a variably equilibrated multimineralic crystal-cargo and compositional fractionation by winnowing during eruptive processes. Hence ‘rapid response’ petrology can untangle complex magmatic and volcanic processes for this eruption, which combined with further study and methodological improvement can increasingly assist in active decision making.
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Bonin, Bernard, Vojtěch Janoušek, and Jean-François Moyen. "Chemical variation, modal composition and classification of granitoids." Geological Society, London, Special Publications 491, no. 1 (December 6, 2019): 9–51. http://dx.doi.org/10.1144/sp491-2019-138.
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AbstractGranites (sensu lato) come in many types and flavours, defining distinct magmatic series/suites/types. A good classification not only gives generally accepted and understandable names to similar rocks but also links the bulk chemical composition to the stoichiometry of the constituent minerals and, potentially, also to the likely source, magmatic evolution and tectonic setting.The ‘ideal’ granitoid classification should be based on chemical criteria amenable to an objective treatment. Statistical analysis helps to identify the most discriminant variables. The key properties are (1) acidity/maficity, (2) alkalinity (balance of Na + K v. Ca), (3) aluminosity (balance of Al v. Ca, Na and K), (4) Fe/Mg balance and (5) Na/K balance and K contents at the given SiO2 level. These are used by successful classifications, e.g. the I/S dichotomy is based mainly on aluminosity, while the Frost et al. (2001; ‘A geochemical classification for granitic rocks', Journal of Petrology, 42, 2033–2048, https://doi.org/10.1093/petrology/42.11.2033) classification includes all but Na/K. Even though it is commonplace to use weight percentages of oxides, we suggest that a better strategy is to employ simple atomic parameters (e.g. millications-based) that can be directly linked to modal proportions and compositions/crystal structure of individual rock-forming minerals. This facilitates a petrological interpretation, which, in turn, can be related to petrogenesis and, ultimately, to likely tectonic setting(s).
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Hasria, Hasria, Arifudin Idrus, and I. Wayan Warmada. "Alteration Alteration, Mineralization and Geochemistry of Metamorphic Rocks Hosted Hydrothermal Gold Deposit at Rumbia Mountains, Bombana Regency, Southeast Sulawesi, Indonesia." Journal of Geoscience, Engineering, Environment, and Technology 4, no. 2 (June 30, 2019): 83. http://dx.doi.org/10.25299/jgeet.2019.4.2.2346.
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In Indonesia, gold is commonly mined from porphyry, epithermal and skarn type deposits that are commonly found in volcanic/magmatic belts. However, were recently numerous gold prospects discovered in association with metamorphic rocks. This paper is intended to describe an alteration and ore mineralogy hosted by metamorphic rocks at Rumbia mountains, Bombana regency, Southeast Sulawesi province, Indonesia. The study area is found the placer and primary gold hosted by metamorphic rocks. The placer gold is evidently derived from gold-bearing quartz veins hosted by Pompangeo Metamorphic Complex (PMC). This study is conducted in three stages, three stages including desk study, field work and laboratory analysis. Desk study mainly covers literature reviews. Field work includes mapping of surface geology, alteration and ore mineralization as well as sampling of representative rocks types, altered rocks and gold-bearing veins. Laboratory analysis includes the petrologic observation of handspecimen samples, petrographic analysis of the thin section and ore microscopy for polished section, XRD (X-ray diffraction), ICP-AES (Inductively Coupled Plasma Atomic Emission Spectroscopy), ICP-MS (Inductively Coupled Plasma Emission Mass Spectrometry and FA/AAS (Fire Assay/Atomic Absorbtion Spectophotometry) analysis. The results shows that the alteration characteristics of hydrothermal gold deposits in Mendoke and Rumbia mountain consist of 3 (three) alterations namely sericitic, argillic dan propylitic. Characteristics of mineralization hydrothermal gold deposits in the research area are generally p related to gold-bearing quartz veins/veinlets consist of chalcopyrite, pyrite, chrysocolla, covellite, cinnabar, magnetite, hematite and goetite in rocks categorized into greenschist facies. There are three generations of veins identified including the first is parallel to the foliations, the second crosscut the first generation of veins/foliations, and the third is of laminated deformed quartz+calcite veins at the late stage. The quartz veins commonly deformed, segmented, massive, laminated, irregular, brecciated, and occasionally sigmoidal. The veins contain erratic gold in various grades from below detection limit <0.0002 ppm to 18,4000 at found in third generation veins which are laminated quartz±calcite in argillic alteration. ppm. The protoliths of metamorphic rocks in Rumbia Mountain, which comes from sedimentary rocks, spesifically pelitic rocks and graywacke. Based on those characteristics, it obviously indicates that the primary gold deposit present in the study area is of orogenic gold deposits type. The orogenic gold deposit is one of the new targets for exploration in Indonesia.