Journal articles: 'Geochemical signatures'

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Brotodewo, Adrienne, Caroline Tiddy, Diana Zivak, Adrian Fabris, David Giles, Shaun Light, and Ben Forster. "Recognising Mineral Deposits from Cover; A Case Study Using Zircon Chemistry in the Gawler Craton, South Australia." Minerals 11, no. 9 (August 25, 2021): 916. http://dx.doi.org/10.3390/min11090916.

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Detrital zircon grains preserved within clasts and the matrix of a basal diamictite sequence directly overlying the Carrapateena IOCG deposit in the Gawler Craton, South Australia are shown here to preserve U–Pb ages and geochemical signatures that can be related to underlying mineralisation. The zircon geochemical signature is characterised by elevated heavy rare-earth element fractionation values (GdN/YbN ≥ 0.15) and high Eu ratios (Eu/Eu* ≥ 0.6). This geochemical signature has previously been recognised within zircon derived from within the Carrapateena orebody and can be used to distinguish zircon associated with IOCG mineralisation from background zircon preserved within stratigraphically equivalent regionally unaltered and altered samples. The results demonstrate that zircon chemistry is preserved through processes of weathering, erosion, transport, and incorporation into cover sequence materials and, therefore, may be dispersed within the cover sequence, effectively increasing the geochemical footprint of the IOCG mineralisation. The zircon geochemical criteria have potential to be applied to whole-rock geochemical data for the cover sequence diamictite in the Carrapateena area; however, this requires understanding of the presence of minerals that may influence the HREE fractionation (GdN/YbN) and/or Eu/Eu* results (e.g., xenotime, feldspar).

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Halla, Jaana. "Highlights on Geochemical Changes in Archaean Granitoids and Their Implications for Early Earth Geodynamics." Geosciences 8, no. 9 (September 17, 2018): 353. http://dx.doi.org/10.3390/geosciences8090353.

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The Archaean (4.0–2.5 Ga) continental crust is mainly composed of granitoids, whose geochemical characteristics are a function of their formation mechanisms and components, as well as physical conditions of their source. Therefore, revealing changes in Archaean geodynamic processes requires understanding of geochemical changes in Archaean granitoids. This paper compares key geochemical signatures in granitoid occurrences from the Eoarchaean to Neoarchaean Eras and aims to highlight changes or variations in their geochemical signatures. The study is performed by exploring and comparing geochemical and geochronological datasets of Archaean granitoids compiled from literature. The results show that two end-members of sodic TTGs (tonalite–trondhjemite–granodiorite) occur throughout the Archaean: low- and high-HREE (heavy rare earth elements) types. A profound change in granitoid geochemistry occurred between 3.0 and 2.5 Ga when multi-source high-K calc-alkaline granitoid batholiths emerged, possibly indicating the onset of modern-type plate tectonics.

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Brenko, Tomislav, Tena Karavidović, Sibila Borojević Šoštarić, and Tajana Sekelj Ivančan. "The contribution of geochemical and mineralogical characterization of iron slags in provenance studies in the Podravina region, NE Croatia." Geologia Croatica 75, no. 1 (February 28, 2022): 165–76. http://dx.doi.org/10.4154/gc.2022.11.

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Archaeological excavations in the Podravina region led to discovery of sites with traces of bloomery iron production during Late Antiquity and the Early Middle Ages. Mineralogical analysis of the slags recognized fayalite as the main mineral phase, while geochemical analysis confirmed high Fe contents, typical for bloomery iron smelting. Based on the previously established occurrences of bog iron ores in the study area, provenance studies were carried out using trace and rare earth elements to create a geochemical signature. Similar shapes and patterns of bog iron ores and iron slag signatures imply a genetic connection between the ore and the slag, as well as variation related to the temporal and spatial context of both slags and ores.

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Steenfelt, A. "Geochemical signatures of gold provinces in South Greenland." Applied Earth Science 109, no. 1 (April 2000): 14–22. http://dx.doi.org/10.1179/aes.2000.109.1.14.

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Tiddy, Caroline, Diana Zivak, June Hill, David Giles, Jim Hodgkison, Mitchell Neumann, and Adrienne Brotodewo. "Monazite as an Exploration Tool for Iron Oxide-Copper-Gold Mineralisation in the Gawler Craton, South Australia." Minerals 11, no. 8 (July 26, 2021): 809. http://dx.doi.org/10.3390/min11080809.

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The chemistry of hydrothermal monazite from the Carrapateena and Prominent Hill iron oxide-copper-gold (IOCG) deposits in the IOCG-rich Gawler Craton, South Australia, is used here to define geochemical criteria for IOCG exploration in the Gawler Craton as follows: Monazite associated with IOCG mineralisation: La + Ce > 63 wt% (where La > 22.5 wt% and Ce > 37 wt%), Y and/or Th < 1 wt% and Nd < 12.5 wt%; Intermediate composition monazite (between background and ore-related compositions): 45 wt% < La + Ce < 63 wt%, Y and/or Th < 1 wt%. Intermediate monazite compositions preserving Nd > 12.5 wt% are considered indicative of Carrapateena-style mineralisation; Background compositions: La + Ce < 45 wt% or Y or Th > 1 wt%. Mineralisation-related monazite compositions are recognised within monazite hosted within cover sequence materials that directly overly IOCG mineralisation at Carrapateena. Similar observations have been made at Prominent Hill. Recognition of these signatures within cover sequence materials demonstrates that the geochemical signatures can survive processes of weathering, erosion, transport and redeposition into younger cover sequence materials that overlie older, mineralised basement rocks. The monazite geochemical signatures therefore have the potential to be dispersed within the cover sequence, effectively increasing the geochemical footprint of mineralisation.

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Hamud, A. Al, S. V. Rasskazov, I. S. Chuvashova, T. A. Yasnygina, and A. Hassan. "Comparative analysis of geochemical signatures for sources of Cenozoic sedimentary deposits laterally to South Baikal." Geology and Environment 2, no. 1 (2022): 110–21. http://dx.doi.org/10.26516/2541-9641.2022.1.110.

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Geochemical signatures of Oligocene and Miocene sedimentary deposits from the Khoygot Paleovalley of Vitim Plateau changed successively over time that reflected change in sources of terrigenic material in the context of the migratory nature of the development of the river network. Geochemical signatures of Eocene-Miocene sedimentary deposits from the eastern (Mishikha-Klyuevka) and western (Osinovka) paleovalleys of the Tankhoy tectonic step of South Baikal were uniform that indicates long-term intake of sedimentary material from a common source. Composition of sedimentary material from paleovalleys of the Tankhoy step was controlled by a limited catchment. After the early Pliocene structural reorganization, geochemical signatures of sedimentary deposits from the eastern part of the Tankhoy tectonic step became similar to those of the Pliocene-Quaternary alluvium frpm the Proto-Manzurka valley of the opposite (north-western) coast of Lake Baikal. It is assumed that the common source of Pliocene-Quaternary sedimentary material was located in Jurassic (Pra-Manzurka) and Upper Jurassic-Lower Cretaceous (eastern part of the Tankhoy tectonic step) sedimentary rocks, disintegrated and eroded on the uplifts of the Primorsky and Khamar-Daban ranges.

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Silva, A. J. F., M. R. Azevedo, B. Valle Aguado, J. A. Nogueira Neto, T. J. S. Santos, and F. D. O. Silva. "Petrographical and geochemical signatures of the Granja paragneisses (Médio Coreaú Domain, NW Ceará, Brasil)." Estudios Geológicos 70, no. 2 (August 25, 2014): e014. http://dx.doi.org/10.3989/egeol.41750.326.

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Ramkumar, Muthuvairavasamy. "Discrimination of tectonic dynamism, quiescence and third order relative sea level cycles of the Cauvery Basin, South India." Annales g?ologiques de la Peninsule balkanique, no. 76 (2015): 19–45. http://dx.doi.org/10.2298/gabp1576.

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Application of integrated stratigraphic modeling of sedimentary basins with the help of sequence and chemostratigraphic methods for improved understanding on the relative roles of depositional pattern and history of a Barremian-Danian stratigraphic record of the Cauvery Basin, India was attempted. Through enumeration of facies characteristics, tectonic structures and geochemical characteristics of the sedimentary rocks the use of geochemical signatures in distinguishing the relative roles of major factors has been evaluated. The results indicate that the geochemical signatures of the sedimentary rocks accurately record the prevalent geological processes and an ability to distinguish them through employing stratigraphic variations of compositional values and discrimination diagrams help in understanding the basinal history better. In addition, predomination of relative sea level fluctuations and active nature of tectonic movements during few time slices, which in turn was overwhelmed by sea level fluctuations are also inferred.

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Silliman, Alan H., and Rick Schrynemeeckers. "Microseepage through evaporite sequences — A Gulf of Suez example." Interpretation 10, no. 1 (December 24, 2021): SB39—SB47. http://dx.doi.org/10.1190/int-2021-0078.1.

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Salt is one of the most effective agents for trapping oil and gas. As a ductile material, it can move and deform surrounding sediments and create traps. However, effective sealing of reservoirs for movement of hydrocarbons along breaching faults or fracture swarms (i.e., macroseepage) is a different mechanism than the movement of hydrocarbons on a molecular scale along grain boundaries and microfractures as happens with microseepage. To address salt seal integrity, Forum Exploration has chosen to evaluate the applicability of passive surface geochemical surveys for mapping hydrocarbons in their onshore West Gebel El Zeit lease in part due to difficulties in seismic imaging through salt and anhydrite sequences. Two economic producing wells have been drilled in the lease, but due to compartmentalization and complexity in the area, three dry wells also have been drilled. Target formations include the Kareem Formation at approximately 2700 m and the Rudeis Formation at approximately 3000 m. The geochemical survey encompasses 100 passive geochemical modules. Passive samplers also have been deployed around two producing wells and one dry well for geochemical calibration. Calibration data indicate positive thermogenic signatures around the two producing wells in contrast to the background or baseline signature from around the dry well. The Kareem Formation calibration signature ranges from approximately C6 to C12 with the Rudeis Formation calibration signature ranging from C5 to C9. This suggests that the Rudeis calibration signature is lighter than the Kareem, in agreement with independent measurement of American Petroleum Institute (API) gravity on produced oil samples (API gravity 41° oil for the Rudeis and 35° oil for the Kareem). A postsurvey well, Fh85-8, has been drilled based on combined geochemical and seismic data results. The well is a Kareem oil discovery, with an initial production of approximately 800 barrels of oil per day. We have developed evidence in this Gulf of Suez example to show that microseepage occurs through substantial salt sequences. Consequently, ultrasensitive passive surface geochemical surveys provide a powerful tool for derisking salt plays.

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Jackson, Matthew G., Janne Blichert-Toft, Saemundur A. Halldórsson, Andrea Mundl-Petermeier, Michael Bizimis, Mark D. Kurz, Allison A. Price, et al. "Ancient helium and tungsten isotopic signatures preserved in mantle domains least modified by crustal recycling." Proceedings of the National Academy of Sciences 117, no. 49 (November 23, 2020): 30993–1001. http://dx.doi.org/10.1073/pnas.2009663117.

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Rare high-3He/4He signatures in ocean island basalts (OIB) erupted at volcanic hotspots derive from deep-seated domains preserved in Earth’s interior. Only high-3He/4He OIB exhibit anomalous182W—an isotopic signature inherited during the earliest history of Earth—supporting an ancient origin of high3He/4He. However, it is not understood why some OIB host anomalous182W while others do not. We provide geochemical data for the highest-3He/4He lavas from Iceland (up to 42.9 times atmospheric) with anomalous182W and examine how Sr-Nd-Hf-Pb isotopic variations—useful for tracing subducted, recycled crust—relate to high3He/4He and anomalous182W. These data, together with data on global OIB, show that the highest-3He/4He and the largest-magnitude182W anomalies are found only in geochemically depleted mantle domains—with high143Nd/144Nd and low206Pb/204Pb—lacking strong signatures of recycled materials. In contrast, OIB with the strongest signatures associated with recycled materials have low3He/4He and lack anomalous182W. These observations provide important clues regarding the survival of the ancient He and W signatures in Earth’s mantle. We show that high-3He/4He mantle domains with anomalous182W have low W and4He concentrations compared to recycled materials and are therefore highly susceptible to being overprinted with low3He/4He and normal (not anomalous)182W characteristic of subducted crust. Thus, high3He/4He and anomalous182W are preserved exclusively in mantle domains least modified by recycled crust. This model places the long-term preservation of ancient high3He/4He and anomalous182W in the geodynamic context of crustal subduction and recycling and informs on survival of other early-formed heterogeneities in Earth’s interior.

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Liu, Xiao-Feng, Shikui Zhai, Xi-Kai Wang, Xinyu Liu, and Xiao-Ming Liu. "Rare Earth Element Geochemistry of Late Cenozoic Island Carbonates in the South China Sea." Minerals 12, no. 5 (May 3, 2022): 578. http://dx.doi.org/10.3390/min12050578.

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Marine carbonates, precipitating from seawater through inorganic geochemical and biogeochemical processes, are considered to have recorded the seawater geochemical signatures reflecting the marine environmental conditions during their formation. However, they are susceptible to post-depositional diagenetic alteration. The redox conditions and chemical composition of the diagenetic fluid may be different from those of the overlying seawater. Therefore, assessing whether carbonate rocks that have experienced variable diagenesis could still preserve primary seawater geochemistry is a prerequisite before inferring ancient marine environments using geochemical tracers such as the cerium anomaly (Ce/Ce*). Here, we investigate rare earth elements plus yttrium (REY) geochemical features of reefal carbonates from the XK-1 core in the Xisha Islands of the South China Sea. We aim to evaluate whether island carbonates have the potential to preserve reliable primary seawater REY geochemical characteristics after experiencing meteoric diagenesis, marine burial diagenesis, or dolomitization. The results show that even after variable diagenetic alteration, all carbonate samples exhibit seawater-like REY patterns, which are characterized by negative Ce anomalies (Ce/Ce* < 1), distinctively high Y/Ho ratios (>44), and uniform depletion of light rare earth elements (LREE) relative to heavy rare earth elements (HREE) ((Pr/Yb)N < 1). This suggests that the original seawater REY signatures are retained, regardless of varying degrees of changes in the mineralogical composition, diagenetic fluid composition, and redox state. The unmodifiable REY characteristics in carbonates during diagenesis can be attributed to three aspects: (1) during meteoric diagenesis, the low REY content of meteoric fluids and the short-term reactions between fluids and carbonates make it difficult to significantly alter the REY composition of carbonates; (2) during marine burial diagenesis, the ubiquitous cementation creates a relatively closed environment that facilitates the inheritance of REY signatures from primary carbonates; (3) during dolomitization, the dolomitizing fluids derived from penecontemporaneous seawater would not destroy but rather promote the preservation of the original seawater REY signatures in dolostones. The Ce/Ce* variations indicate that the Xisha carbonates have been deposited under constantly oxic conditions since the Neogene, consistent with paleontological and redox-sensitive element geochemical evidence.

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Ullmann, CV, HJ Campbell, R. Frei, and C. Korte. "Geochemical signatures in Late Triassic brachiopods from New Caledonia." New Zealand Journal of Geology and Geophysics 57, no. 4 (October 2, 2014): 420–31. http://dx.doi.org/10.1080/00288306.2014.958175.

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Wyborn, L. A. I., R. W. Page, and A. J. Parker. "Geochemical and Geochronological Signatures in Australian Proterozoic Igneous Rocks." Geological Society, London, Special Publications 33, no. 1 (1987): 377–94. http://dx.doi.org/10.1144/gsl.sp.1987.033.01.26.

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Abshire, Michelle L., Jeremy D. Owens, Jessica Cofrancesco, Maik Inthorn, and Natascha Riedinger. "Geochemical signatures of redepositional environments: The Namibian continental margin." Marine Geology 429 (November 2020): 106316. http://dx.doi.org/10.1016/j.margeo.2020.106316.

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Whalen, Joseph B., Leslie R. Fyffe, Frederick J. Longstaffe, and George A. Jenner. "The position and nature of the Gander–Avalon boundary, southern New Brunswick, based on geochemical and isotopic data from granitoid rocks." Canadian Journal of Earth Sciences 33, no. 2 (February 1, 1996): 129–39. http://dx.doi.org/10.1139/e96-013.

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In southern New Brunswick, the Gander–Avalon boundary is obscured by boundary-parallel faults and various cover sequences. Siluro-Devonian granites, which intrude unequivocal Gander or Avalon rocks, display exclusively negative (−1.9 ± 1.0) and positive (+1.9 ± 0.7) εNd(T) signatures, respectively. Such contrasting Nd isotopic signatures, combined with other geochemical differences between plutons, are potentially valuable tools for terrane analysis. Nine small Devonian plutons intruding the boundary zone fall into contrasting geochemical groups with (La/Lu)N <4 and >4. The former are topaz-bearing granites, while the latter are volcanic-arc-type granites. Except for one pluton, with an εNd(T) signature of –2.0, εNd(T) values range from –0.4 to +0.7, spanning the gap between "type" Avalon and "type" Gander plutons. These results suggest the plutons sampled either (i) stratigraphically overlapping or tectonically interleaved Gander and Avalon basement rocks, or (ii) a distinct basement source beneath the boundary zone. Our results demonstrate that the Gander–Avalon boundary in southern New Brunswick is not a simple throughgoing crustal fault, and that the Gander and Avalon zones are underlain by different continental basement blocks. Comparison with results from Newfoundland and Nova Scotia suggests that these basement blocks are continuous throughout the Canadian Appalachians.

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Wolff, Brian A., Brett M. Johnson, and Chad M. Landress. "Classification of hatchery and wild fish using natural geochemical signatures in otoliths, fin rays, and scales of an endangered catostomid." Canadian Journal of Fisheries and Aquatic Sciences 70, no. 12 (December 2013): 1775–84. http://dx.doi.org/10.1139/cjfas-2013-0116.

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Endangered and endemic June sucker (JS, Chasmistes liorus) have been stocked for many years to prevent extinction in Utah Lake, Utah. When unmarked fish appeared in the lake at higher rates than expected from tag loss, we sought to determine if 87Sr/86Sr and Sr/Ca (signatures) in otoliths, fin rays, and scales could be used to identify whether stocking had created a naturally reproducing population. Signatures from otoliths and fin rays suggested that approximately 38% (12 of 31) of unmarked JS probably came from the Fisheries Experimental Station (FES) hatchery in Logan, Utah, and a minimum of 13% (four of 31) of unmarked JS had signatures that strongly indicated that they were of wild origin. The remaining JS (15 of 31) could not be assigned to any particular location because of signature overlap. While scales were not useful for determining fish provenance, we found a nearly 1:1 relationship between pelvic fin and otolith 87Sr/86Sr. Thus, fin sections appear to provide a nonlethal structure for laser ablation microchemical analysis to determine origins of unknown origin JS in the future.

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MINGRAM, BIRGIT. "The Erzgebirge, Germany, a subducted part of northern Gondwana: geochemical evidence for repetition of early Palaeozoic metasedimentary sequences in metamorphic thrust units." Geological Magazine 135, no. 6 (November 1998): 785–801. http://dx.doi.org/10.1017/s0016756898001769.

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One of the major metamorphic terranes of the Bohemian Massif, the Erzgebirge, is interpreted to record a subducted part of a Palaeozoic margin of Gondwana. A geochemical study on non-calcareous metasediments from the various metamorphic units from lower greenschist to granulite facies metamorphism supports a recently established thrust model. Geochemical discrimination and correlation from the metasediments of the Erzgebirge suggest repetition of an early Palaeozoic metasedimentary sequence in metamorphic thrust units. This new finding is in line with recent radiometric dating of intercalated metarhyolitic rocks, which yielded ages of around 480 Ma. It is furthermore supported by correlation with a low-grade standard section in Thuringia, which represents the transition from an orogenic belt to a passive margin setting, with highly mature sediments. Significant geochemical signatures have been identified in three different lithotypes, which reappear in at least three metamorphic units of the Erzgebirge. Geochemical correlation of these units was established using simple comparison of averages and with statistical techniques. The identification of significant geochemical signatures from different lithotypes in metamorphic suites has important implications for terrane analysis and reconstruction of ancient tectonic settings.The repetition of lithologies and their distinct chemical compositions in progressively metamorphosed units is useful for examining element mobility during Barrovian metamorphism. Statistical comparison implies that Li is progressively depleted from the greenschist to amphibolite facies, whereas Ca exhibits some enrichment. All the other elements studied are considered to be immobile.

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Joye, S. B., I. R. MacDonald, J. P. Montoya, and M. Peccini. "Geophysical and geochemical signatures of Gulf of Mexico seafloor brines." Biogeosciences 2, no. 3 (October 28, 2005): 295–309. http://dx.doi.org/10.5194/bg-2-295-2005.

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Abstract. Geophysical, temperature, and discrete depth-stratified geochemical data illustrate differences between an actively venting mud volcano and a relatively quiescent brine pool in the Gulf of Mexico along the continental slope. Geophysical data, including laser-line scan mosaics and sub-bottom profiles, document the dynamic nature of both environments. Temperature profiles, obtained by lowering a CTD into the brine fluid, show that the venting brine was at least 10°C warmer than the bottom water. At the brine pool, thermal stratification was observed and only small differences in stratification were documented between three sampling times (1991, 1997 and 1998). In contrast, at the mud volcano, substantial temperature variability was observed, with the core brine temperature being slightly higher than bottom water (by 2°C) in 1997 but substantially higher than bottom water (by 19°C) in 1998. Detailed geochemical samples were obtained in 2002 using a device called the "brine trapper" and concentrations of dissolved gases, major ions and nutrients were determined. Both brines contained about four times as much salt as seawater and steep concentration gradients of dissolved ions and nutrients versus brine depth were apparent. Differences in the concentrations of calcium, magnesium and potassium between the two brine fluids suggest that the fluids are derived from different sources, have different dilution/mixing histories, or that brine-sediment reactions are more important at the mud volcano. Substantial concentrations of methane, ammonium, and silicate were observed in both brines, suggesting that fluids expelled from deep ocean brines are important sources of these constituents to the surrounding environment.

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Walther, Benjamin D., Simon R. Thorrold, and John E. Olney. "Geochemical Signatures in Otoliths Record Natal Origins of American Shad." Transactions of the American Fisheries Society 137, no. 1 (January 2008): 57–69. http://dx.doi.org/10.1577/t07-029.1.

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Nicholson, Keith. "Contrasting mineralogical-geochemical signatures of manganese oxides; guides to metallogenesis." Economic Geology 87, no. 5 (August 1, 1992): 1253–64. http://dx.doi.org/10.2113/gsecongeo.87.5.1253.

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Xia, Xinyu, and Yongli Gao. "Validity of geochemical signatures of abiotic hydrocarbon gases on Earth." Journal of the Geological Society 179, no. 3 (October 19, 2021): jgs2021–077. http://dx.doi.org/10.1144/jgs2021-077.

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Abiotic synthesis has been hypothesized as a mechanism for occurrences of hydrocarbon gases with atypical molecular and isotopic compositions. This paper provides biotic interpretations of these atypical compositions, as follows: (1) microbial CH4 oxidation and CO2-sourced methanogenesis may enrich 13C in hydrothermal CH4; (2) microbial hydrocarbon generation using serpentinization-derived H2 may deplete deuterium in hydrocarbons; (3) three processes may cause isotopic reversal with the carbon number in biotic hydrocarbons (the decrease of kinetic isotope effect (KIE) with the increase of carbon number during alkane biodegradation, inverse KIE during the thermal decomposition of higher alkanes and isotopic fractionation during gas diffusion in rock samples); (4) random scission of long alkyl chains may form the exponential distribution of alkane abundance with respect to carbon number (the ‘Schulz–Flory distribution’); (5) isotopic compositions are often not equilibrated; even if they are, the equilibrium temperatures are not necessarily the same as the temperature of hydrocarbon generation. Case studies demonstrate that previously proposed abiotic hydrocarbon gases in continental serpentinite-hosted seepages, continental or oceanic hydrothermal vents, volcanic emissions, gas fields in volcanic reservoirs and fluid inclusions in alkaline or granitic rocks were formed by various biotic processes. The occurrence of abiotic hydrocarbon gas with decisive evidence is limited to fluid inclusions in some mantle minerals.Supplementary material: Expressions for isotopic fractionation of CH4 and model details of the Xujiaweizi gas are available at https://doi.org/10.6084/m9.figshare.c.5660278

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Nguyen, Anh, Rinat Gabitov, Angel Jimenez, Andrew Dygert, Jac Varco, Alberto Pérez-Huerta, Artas Migdisov, Varun Paul, Brenda Kirkland, and Padmanava Dash. "Retaining Geochemical Signatures during Aragonite-Calcite Transformation at Hydrothermal Conditions." Minerals 11, no. 10 (September 28, 2021): 1052. http://dx.doi.org/10.3390/min11101052.

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Transformation of aragonite, a mineral phase metastable at Earth’s surface, to calcite widely occurs in both sedimentary and metamorphic systems with the presence of an aqueous phase. The transformation process can affect geochemical signatures of aragonite (a protolith). This study focused on quantification of the retention of Mg/Ca and Sr/Ca ratios, and δ18O during the transformation process as well as evaluation of the transformation rate. To investigate the effect of transformation from aragonite to calcite on elemental and stable isotope ratios, we conducted a series of experiments in NaCl solutions at temperatures between 120 and 184 °C. Two additional experiments at 250 °C were conducted to estimate the transformation rate of aragonite to calcite. Protolith materials consist of (1) synthetic (Mg; Sr-bearing or non-Mg; Sr bearing) needle-shaped microcrystals of aragonite (<5 µm in size) and (2) larger chips (>100 µm in size) of natural aragonite. X-ray diffraction (XRD) showed that microcrystals successfully transformed to calcite within 30 h and scanning electron microscopy (SEM) yielded a change in the crystal size to >10 µm in rhombohedral shape. Electron backscatter diffraction (EBSD) of the larger aragonite chips showed that transformation to randomly oriented calcite occurred at the rims and along the cracks while the core retained an aragonite crystal structure. Isotope-ratio mass spectrometry (IRMS) analyses showed that calcite δ18O was controlled by temperature and δ18O of the solution. The obtained calibration curve of isotope fractionation factor versus temperature is consistent with other studies. Inductively coupled plasma optical emission spectroscopy (ICP-OES) analyses showed that calcite partially or completely retained Mg/Ca and Sr/Ca ratios through the transformation.

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Kerr, Andrew C., Andrew D. Saunders, John Tarney, Neil H. Berry, and Victoria L. Hards. "Depleted mantle-plume geochemical signatures: No paradox for plume theories." Geology 23, no. 9 (1995): 843. http://dx.doi.org/10.1130/0091-7613(1995)023<0843:dmpgsn>2.3.co;2.

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Joye, S. B., I. R. MacDonald, J. P. Montoya, and M. Peccini. "Geophysical and geochemical signatures of Gulf of Mexico seafloor brines." Biogeosciences Discussions 2, no. 3 (May 31, 2005): 637–71. http://dx.doi.org/10.5194/bgd-2-637-2005.

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Abstract. Geophysical, temperature, and discrete depth-stratified geochemical data illustrate differences between an actively venting mud volcano and a relatively quiescent brine pool in the Gulf of Mexico along the continental slope. Geophysical data, including laser-line scan mosaics and sub-bottom profiles, document the dynamic nature of both environments. Temperature profiles, obtained by lowering a CTD into the brine fluid, show that the venting brine was at least 10°C warmer than the bottom water. At the brine pool, two thermoclines were observed, one directly below the brine-seawater interface and a second about one meter below the first. At the mud volcano, substantial temperature variability was observed, with the core brine temperature being either slightly (~2°C in 1997) or substantially (19°C in 1998) elevated above bottom water temperature. Geochemical samples were obtained using a device called the "brine trapper" and concentrations of dissolved gases, major ions and nutrients were determined using standard techniques. Both brines contained about four times as much salt as seawater and steep concentration gradients of dissolved ions and nutrients versus brine depth were apparent. Differences in the concentrations of calcium, magnesium and potassium between the two brine fluids suggests that the fluids are derived from different sources or that brine-sediment reactions are more important at the mud volcano than the brine pool. Substantial concentrations of methane and ammonium were observed in both brines, suggesting that fluids expelled from deep ocean brines are important sources of methane and dissolved inorganic nitrogen to the surrounding environment.

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Fagel, Nathalie, Luc André, and Pierre Debrabant. "Multiple seawater-derived geochemical signatures in Indian oceanic pelagic clays." Geochimica et Cosmochimica Acta 61, no. 5 (March 1997): 989–1008. http://dx.doi.org/10.1016/s0016-7037(96)00392-4.

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Kuscu, Ilkay, Gonca GençAlioglu-Kuscu, and Ayhan Erler. "Geochemical Signatures of Granitoids Associated with Skarns in Central Anatolia." International Geology Review 43, no. 8 (August 2001): 722–35. http://dx.doi.org/10.1080/00206810109465044.

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Wielicki, Matthew M., T. Mark Harrison, and Axel K. Schmitt. "Geochemical signatures and magmatic stability of terrestrial impact produced zircon." Earth and Planetary Science Letters 321-322 (March 2012): 20–31. http://dx.doi.org/10.1016/j.epsl.2012.01.009.

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Başpınar Tuncay, Ebru, Ekin Koken, Mustafa Kuşcu, Oya Cengiz, Fatih Aydemir, and Rahman Raimov. "Geological-geochemical signatures of opal occurrences in Keçiborlu (Isparta-Turkey)." Pamukkale University Journal of Engineering Sciences 28, no. 6 (2022): 840–50. http://dx.doi.org/10.5505/pajes.2021.84769.

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Bhattacharya, S., A. K. Chaudhary, A. K. Saw, P. Das, and D. Chatterjee. "Mafic granulite xenoliths in the Chilka Lake suite, Eastern Ghats Belt, India: evidence of deep-subduction of residual oceanic crust." Solid Earth Discussions 4, no. 2 (November 5, 2012): 1379–410. http://dx.doi.org/10.5194/sed-4-1379-2012.

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Abstract. Granulite xenoliths preserve key geochemical and isotopic signatures of their mantle source regions. Mafic granulite and pyroxinite xenoliths within massif-type charnockitic rocks from the Eastern Ghats Belt have recently been reported by us. The mafic granulite xenoliths from the Chilka Lake granulite suite with abundant prograde biotite are geochemically akin to Oceanic Island Basalt (OIB). They can be distinguished from the hornblende-mafic granulite xenoliths with signatures of Arc-derived basalt occurring in the other suites of the Eastern Ghats Belt. These two groups of xenoliths in the Paleoproterozoic Eastern Ghats Province have quite distinct Nd-model ages- 1.9 Ga and 2.5 Ga respectively, which may be interpreted as their crustal residence ages. Strong positive Nb anomalies, indicating subducted oceanic crust in the source, LREE enrichment and strongly fractionated REE pattern are key geochemical signatures attesting to their origin as OIB-type magma. Also low Yb and Sc contents and high (La / Yb)N ratios can be attributed to melting in the presence of residual garnet and hence at great depths (> 80 km). The variable enrichment in radiogenic 87Sr, between 0.70052 and 0.71092 at 1.9 Ga and less radiogenic 143Nd between ε-1.54 and 7.46 are similar to those of the OIBs compared to MORBs. As OIBs commonly contain some recycled oceanic crust in their sources, we suggest that the residue of the oceanic crust from a previous melting event (~ 2.5 Ga) that produced the Arc-derived basalts (protoliths of hornblende-mafic granulite xenoliths) could have subducted to great depths and mechanically mixed with the mantle peridotite. A subsequent re-melting event of this mixed source might have occurred at ca. 1.9 Ga as testified by the crustal residence ages of the biotite-mafic granulite xenoliths of the Chilka Lake granulite suite.

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Rooker, Jay R., R. J. David Wells, Piero Addis, Haritz Arrizabalaga, Miguel Baptista, Giovanni Bearzi, Michael A. Dance, et al. "Natural geochemical markers reveal environmental history and population connectivity of common cuttlefish in the Atlantic Ocean and Mediterranean Sea." Journal of The Royal Society Interface 17, no. 168 (July 2020): 20200309. http://dx.doi.org/10.1098/rsif.2020.0309.

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Natural markers (δ 13 C and δ 18 O stable isotopes) in the cuttlebones of the European common cuttlefish ( Sepia officinalis ) were determined for individuals collected across a substantial portion of their range in the Northeast Atlantic Ocean (NEAO) and Mediterranean Sea. Cuttlebone δ 13 C and δ 18 O were quantified for core and edge material to characterize geochemical signatures associated with early (juvenile) and recent (sub-adult/adult) life-history periods, respectively. Regional shifts in cuttlebone δ 13 C and δ 18 O values were detected across the 12 sites investigated. Individuals collected from sites in the NEAO displayed more enriched δ 13 C and δ 18 O values relative to sites in the Mediterranean Sea, with the latter also showing salient differences in both markers among western, central and eastern collection areas. Classification success based on cuttlebone δ 13 C and δ 18 O values to four geographical regions (NEAO, western, central and eastern Mediterranean Sea) was relatively high, suggesting that environmental conditions in each region were distinct and produced area-specific geochemical signatures on the cuttlebones of S. officinalis . A modified δ 13 C and δ 18 O baseline was developed from sites proximal to the Strait of Gibraltar in both the NEAO and Mediterranean Sea to assess potential mixing through this corridor. Nearly, all (95%) of δ 13 C and δ 18 O signatures of S. officinalis collected in the area of the NEAO closest to the Strait of Gibraltar (Gulf of Cadiz) matched the signatures of specimens collected in the western Mediterranean, signifying potential movement and mixing of individuals through this passageway. This study extends the current application of these geochemical markers for assessing the natal origin and population connectivity of this species and potentially other taxa that inhabit this geographical area.

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Edwards, D. S., R. E. Summons, J. M. Kennard, R. S. Nicoll, J. Bradshaw, M. Bradshaw, C. B. Foster, G. W. O'Brien, and J. E. Zumberge. "GEOCHEMICAL CHARACTERISTICS OF PALAEOZOIC PETROLEUM SYSTEMS IN NORTHWESTERN AUSTRALIA." APPEA Journal 37, no. 1 (1997): 351. http://dx.doi.org/10.1071/aj96022.

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Isotopic and biomarker analyses carried out on Cambrian to Permian oils and source rocks in the Arafura, Bonaparte (Petrel Sub-basin) and Canning Basins have been used to geochemically characterise five distinct petroleum systems within the Larapintine and Gondwanan Petroleum Supersystems. The Larapintine 1 Petroleum System is characterised by isotopically light, free hydrocarbons in the Arafura Basin (613Csat = −32 %o Arafura-1) which have been correlated to kerogens of similar isotopic signature within the Middle Cambrian Jigaimara Formation. The richness and maturity of these source rocks indicate that an effective Larapintine 1 Petroleum System may exist in the northern parts of the Arafura Basin. Larapintine 2 oils, with Gloeocapsomorpha prisca-type signatures, are found on the Barbwire- Dampier Terraces and Admiral Bay Fault Zone in the Canning Basin. These oils can be correlated to source rocks in the Lower Ordovician Goldwyer Formation on the Barbwire Terrace and the Bongabinni Formation in the Admiral Bay Fault Zone by their diagnostic odd- carbon-number preference in the C15—CJ9 n-alkanes. Larapintine 3 oils are derived from Upper Devonian marine carbonates in the Canning Basin and Petrel Sub- basin and have a diagnostic biomarker signature which includes a predominance of steranes relative to diasteranes and abundant gammacerane and 30- norhopanes, similar to those observed in the Upper Devonian Gogo and Pillara Formations. Larapintine 4 oils are derived from Lower Carboniferous marine, clay- rich mudstones in both the Petrel Sub-basin and Canning Basin. They are isotopically light (mean δ13C sat = −28 %o) and have a unique terpane signature which has been identified within the Milligans Formation. Gondwanan 1 Petroleum System hydrocarbons, represented here by the Petrel-4 condensate, have a heavy isotopic signature (δ13C sat = −24 %o) which, coupled with an abundance of the diasterane and diahopane biomarkers, indicates derivation from Permian deltaic source facies. Recognition of the diagnostic geochemical components of each Palaeozoic petroleum system has led to the identification of Permian-like isotopic signatres in some hydrocabon accumulations in the Timor Sea that were previously attributed to Mesozoic sources.

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Walther, Benjamin D., and Simon R. Thorrold. "Continental-scale variation in otolith geochemistry of juvenile American shad (Alosa sapidissima)." Canadian Journal of Fisheries and Aquatic Sciences 65, no. 12 (December 2008): 2623–35. http://dx.doi.org/10.1139/f08-164.

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We assembled a comprehensive atlas of geochemical signatures in juvenile American shad ( Alosa sapidissima ) to discriminate natal river origins on a large spatial scale and at a high spatial resolution. Otoliths and (or) water samples were collected from 20 major spawning rivers from Florida to Quebec and were analyzed for elemental (Mg:Ca, Mn:Ca, Sr:Ca, and Ba:Ca) and isotope (87Sr:86Sr and δ18O) ratios. We examined correlations between water chemistry and otolith composition for five rivers where both were sampled. While Sr:Ca, Ba:Ca, 87Sr:86Sr, and δ18O values in otoliths reflected those ratios in ambient waters, Mg:Ca and Mn:Ca ratios in otoliths varied independently of water chemistry. Geochemical signatures were highly distinct among rivers, with an average classification accuracy of 93% using only those variables where otolith values were accurately predicted from water chemistry data. The study represents the largest assembled database of otolith signatures from the entire native range of a species, encompassing approximately 2700 km of coastline and 19 degrees of latitude and including all major extant spawning populations. This database will allow reliable estimates of natal origins of migrating ocean-phase American shad from the 2004 annual cohort in the future.

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Nadoll, Patrick, Meike Rehm, Florian Duschl, Reiner Klemd, Dennis Kraemer, and Marta Sośnicka. "REY and Trace Element Chemistry of Fluorite from Post-Variscan Hydrothermal Veins in Paleozoic Units of the North German Basin." Geosciences 8, no. 8 (July 29, 2018): 283. http://dx.doi.org/10.3390/geosciences8080283.

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Hydrothermal fluorites from Paleozoic sedimentary rocks and volcanic units in the North German Basin (NGB) have been investigated to create a petrographic and geochemical inventory—with particular focus on strategic elements such as rare earth elements (REE)—and to uncover possible links between the post-Variscan hydrothermal mineralization in the NGB and bordering areas such as the Harz Mountains and Flechtingen Calvörde Block (FCB). Fluorites from ten localities underwent a detailed petrographic examination, including SEM-BSE/CL imagery, and were compositionally analysed using LA-ICP-MS. Overall, REY concentrations are comparatively low in fluorite from all investigated areas—the median sum of REY ranges from 0.3 to 176 ppm. EuropiumCN anomalies are slightly negative or absent, indicating that either the formation fluid experienced temperatures above 250 °C or that fluid-rock interactions and REE enrichment was likely controlled by the source rock (i.e., volcanic) composition and complexation processes. Fluorites from the Altmark-Brandenburg Basin (ABB) and the Lower Saxony Basin (LSB) display distinctly different REYCN signatures, suggesting that fluid compositions and genetic processes such as fluid-rock interaction differed significantly between the two areas. Complex growth zones and REYCN signatures in fluorite from the ABB and the FCB reflect geochemical variability due to adsorption processes and intrinsic crystallographic controls and imply that they are genetically related. Two petrographically and geochemically distinct generations are observed: Fluorite I—light SEM shades, relatively enriched in LREE; Fluorite II—darker SEM shades, comparatively depleted LREE, slightly higher HREE concentrations. These fluorite generations represent zoned (or cyclical) growth within a single progressive hydrothermal event and do not reflect a secondary remobilization process. We demonstrate that increasing Tb/La ratios and decreasing La/Ho ratios can be the result of continuous zoned growth during a single mineralizing event, with significant compositional variations on a micron-scale. This has implications for the interpretation of such trends and hence the inferred genetic evolution of fluorite that displays such geochemical patterns. The complex micro-scale intergrowth of these generations stresses the need for detailed petrographic investigations when geochemical data are collected and interpreted for mineral exploration.

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Massawe, Ronald Joseph, and David R. Lentz. "Petrochemistry and U–Pb (zircon) age of porphyry dykes at the McKenzie Gulch porphyry–skarn Cu–Ag–Au deposit, north-central New Brunswick, Canada: implications for emplacement age, tectonic setting, and mineralization potential." Canadian Journal of Earth Sciences 57, no. 4 (April 2020): 427–52. http://dx.doi.org/10.1139/cjes-2018-0313.

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North- to northeast-trending intermediate to felsic porphyry dykes in the McKenzie Gulch (MG) area intrude Upper Ordovician through Silurian calcareous sedimentary rocks of the Matapédia Group. These dykes are spatially associated with numerous copper–silver skarn occurrences. In this area, two distinct suites of dykes are recognized: plagioclase–hornblende porphyry (P–H) and quartz–plagioclase porphyry (Q–P). These suites yielded U–Pb (zircon) ages of 386.2 ± 3.1 Ma and 386.4 ± 3.3 Ma, respectively, indicating a coeval relationship and similar genesis despite slight geochemical and petrographical differences. Geochemical data indicate that the dykes are granodioritic to granitic to slightly tonalitic in composition with I-type and slab failure signatures. When compared with other granitoids in the region, the Murdochville suite in Gaspésie, Québec, is the only intrusion that exhibits slab failure magmatic signatures similar to the MG dykes. Magmas with slab failure signatures are compositionally similar to tonalite–trondhjemite–granodiorite (TTG) suites and adakites. They exhibit low Y and Yb concentrations and subsequent high Sr/Y and La/Yb ratios, which are interpreted to be the result of melting of subducting slab and mantle during the waning stages of collision and consequent slab failure. These processes were followed by assimilation and fractional crystallization of minerals such as hornblende and clinopyroxene (± titanite), which preferentially partition Y and heavy rare earth elements (HREE) in the absence of significant plagioclase. Magmas with similar geochemical characteristics worldwide have been proposed to be an important source for metals in most porphyry Cu and skarn deposits and consequently are a target during mineral exploration.

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UMAMAHESWARAN, RAMAN, G. V. R. PRASAD, ARKA RUDRA, and SURYENDU DUTTA. "BIOMARKER SIGNATURES IN TRIASSIC COPROLITES." PALAIOS 34, no. 10 (October 15, 2019): 458–67. http://dx.doi.org/10.2110/palo.2019.023.

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ABSTRACT Coprolites are traditionally analyzed from a morphological perspective. Few studies exist from an organic geochemical perspective, and most of these consider recent specimens. This study represents an analysis of coprolites from deep time, using both traditional one-dimensional and also two-dimensional gas chromatography-mass spectrometry. We find organic molecules preserved in coprolites from the Triassic, and that both dietary habits of the defecators and paleoenvironment can be interpreted using comparative distributions of biomarker abundances in the coprolites. Steranes having 27 carbon atoms are known to be derived from animal steroids whereas those with 29 carbon atoms are known to be derived from plant steroids. The predominance of steranes with 27 carbon atoms over those with 29 carbon atoms in a non-marine environment was interpreted as evidence for the defecator(s) being predominantly carnivorous or possibly omnivorous. A series of tricyclic terpanes ranging from C19 to C28 was examined to determine the environment. The present study suggests that one or possibly all of the defecators may have been small-medium carnivores that lived in an aquatic or near aquatic setting.

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Liu, Haiming, and Georges Beaudoin. "Geochemical signatures in native gold derived from Au-bearing ore deposits." Ore Geology Reviews 132 (May 2021): 104066. http://dx.doi.org/10.1016/j.oregeorev.2021.104066.

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Remya, J., R. S. Prasanth, and A. P. Pradeepkumar. "Geochemical signatures of gneisses and granulites of Marthandam, Tamil Nadu, India." Bulletin of Pure & Applied Sciences- Geology 39f, no. 1 (2020): 1. http://dx.doi.org/10.5958/2320-3234.2020.00001.3.

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Thorrold, Simon, Danielle Zacherl, and Lisa Levin. "Population Connectivity and Larval Dispersal Using Geochemical Signatures in Calcified Structures." Oceanography 20, no. 3 (September 1, 2007): 80–89. http://dx.doi.org/10.5670/oceanog.2007.31.

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Volkova, N. I., A. E. Frenkel, V. I. Budanov, and G. G. Lepezin. "Geochemical signatures for eclogite protolith from the Maksyutov Complex, South Urals." Journal of Asian Earth Sciences 23, no. 5 (September 2004): 745–59. http://dx.doi.org/10.1016/s1367-9120(03)00128-7.

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Hall, Gwendy E. M., Judy E. Vaive, and Peter Button. "Detection of past underground nuclear events by geochemical signatures in soils." Journal of Geochemical Exploration 59, no. 3 (September 1997): 145–62. http://dx.doi.org/10.1016/s0375-6742(97)00019-8.

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Zhang, Tongwei, Geoffrey S. Ellis, Clifford C. Walters, Simon R. Kelemen, Kang-shi Wang, and Yongchun Tang. "Geochemical signatures of thermochemical sulfate reduction in controlled hydrous pyrolysis experiments." Organic Geochemistry 39, no. 3 (March 2008): 308–28. http://dx.doi.org/10.1016/j.orggeochem.2007.12.007.

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Chen, Duo Fu, Lawrence M. Cathles, and Harry H. Roberts. "The geochemical signatures of variable gas venting at gas hydrate sites." Marine and Petroleum Geology 21, no. 3 (March 2004): 317–26. http://dx.doi.org/10.1016/j.marpetgeo.2003.12.003.

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López, D. L., P. A. Araujo, I. Delgado Outeiriño, J. A. Cid, and G. Astray. "Geochemical signatures of the groundwaters from Ourense thermal springs, Galicia, Spain." Sustainable Water Resources Management 5, no. 1 (March 5, 2018): 103–16. http://dx.doi.org/10.1007/s40899-018-0239-3.

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Lett, Ray E. "Geochemical signatures around massive sulphide deposits in southern British Columbia, Canada." Geological Society, London, Special Publications 185, no. 1 (2001): 301–21. http://dx.doi.org/10.1144/gsl.sp.2001.185.01.14.

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Massonne, Hans-Joachim, and Anita Czambor. "Geochemical signatures of Variscan eclogites from the Saxonian Erzgebirge, central Europe." Geochemistry 67, no. 1 (May 2007): 69–83. http://dx.doi.org/10.1016/j.chemer.2006.07.001.

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Støren, Eivind W. N., Øyvind Paasche, Ann M. Hirt, and Monika Kumari. "Magnetic and geochemical signatures of flood layers in a lake system." Geochemistry, Geophysics, Geosystems 17, no. 10 (October 2016): 4236–53. http://dx.doi.org/10.1002/2016gc006540.

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Mosusu, Nathan, Angela Bokuik, Michael Petterson, and Robert Holm. "Stream Sediment Datasets and Geophysical Anomalies: A Recipe for Porphyry Copper Systems Identification—The Eastern Papuan Peninsula Experience." Geosciences 11, no. 7 (July 20, 2021): 299. http://dx.doi.org/10.3390/geosciences11070299.

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Airborne magnetic and radiometric datasets have, over the past few years, become powerful tools in the identification of porphyry systems which may host economic porphyry copper–gold–molybdenum ore bodies. Magnetisation contrasts with the unaltered host rocks, coupled with the elevated radiometric signature, compared to the host rock, makes identification of large-scale porphyry copper systems possible. Integrating these two different datasets with stream sediment data and other geochemical exploration methods results in a higher degree of confidence. Stream sediment data were analysed to see the distribution of copper and gold elements throughout the study area, located within the Eastern Papuan Peninsula of Papua New Guinea. Airborne geophysics data over the same area were also processed for magnetic and radiometric responses. The processing of the magnetic data revealed several magnetic anomalies related to concealed intrusive rock units, with associated radiometric signatures. The distribution of gold and copper anomalism was correlated with the geology and geophysical signatures. Results indicate varying degrees of correlation, with some areas showing a strong correlation between gold/copper occurrence and geophysical signatures, compared to other areas. Some factors that we believe impact the level of correlation may include tectonic history, volcanic cover, and weathering patterns. We recommend caution when applying multi-data exploration for porphyry copper systems.

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Jenner, G. A., and H. Scott Swinden. "The Pipestone Pond Complex, central Newfoundland: complex magmatism in an eastern Dunnage Zone ophiolite." Canadian Journal of Earth Sciences 30, no. 3 (March 1, 1993): 434–48. http://dx.doi.org/10.1139/e93-032.

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Ophiolitic rocks are preserved in both the Notre Dame and Exploits subzones in the Dunnage Zone of the Newfoundland Appalachians. Ophiolites in the Exploits Subzone are generally less well preserved and exposed than their Notre Dame Subzone counterparts and, consequently, have received less attention in the literature.The Pipestone Pond Complex is an Exploits Subzone ophiolitic sequence, which outcrops on the western side of a structural window through the Exploits Subzone into the underlying Gander Zone. It includes a basal harzburgite, which passes upwards into a cumulate pyroxenite and gabbro sequence, and thence into isotropic gabbro intruded by pegmatitic gabbro, diabase, and plagiogranite. There is no sheeted dyke unit. Pillow lava occurs at the top of the sequence but is not observed to be in stratigraphic contact with the intrusive rocks. The ophiolitic rocks are structurally disrupted and no single cross section traverses the complete ophiolitic stratigraphy.Although the stratigraphic sequence of the Pipestone Pond Complex is relatively straightforward, whole-rock geochemical and Nd/Sm isotopic data provide evidence for a complex magmatic history. The intrusive rocks have εNd(t) ranging from −1.1 to + 4 and geochemical signatures indicating derivation from depleted and refractory mantle sources that were clearly influenced by subduction. Within the intrusive rocks, there are no simple petrogenetic relationships among the gabbros and dykes and trondhjemites. The extrusive rocks, in contrast, have εNd(t) of + 7.3 and geochemical signatures similar to those of normal mid-ocean-ridge basalts. They represent magmatism derived from depleted oceanic mantle, not affected by the subducted slab.The tectonic interpretation of the Pipestone Pond Complex is hampered by a lack of definitive evidence for the relative age of the arc-related plutonic rocks and the non-arc-related extrusive rocks. Two possible interpretations are (i) the initiation of subduction under oceanic crust and (ii) arc rifting. The Pipestone Pond Complex is geologically and geochemically analogous to the Boil Mountain Complex in Maine, and together they may form part of an extensive ophiolitic terrane that was emplaced upon the Gondwanan continental margin prior to its collision with Laurentia.

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Freire, Antonio Fernando Menezes, Ryo Matsumoto, and Fumio Akiba. "Geochemical Analysis as a Complementary Tool to Estimate the Uplift of Sediments Caused by Shallow Gas Hydrates in Mounds at the Seafloor of Joetsu Basin, Eastern Margin of the Japan Sea." Journal of Geological Research 2012 (October 2, 2012): 1–14. http://dx.doi.org/10.1155/2012/839840.

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The Holocene sediments of the eastern margin of the Japan Sea are characterized by high total organic carbon (TOC) and total nitrogen (TN) contents, low TOC/TN and TS/TOC values with enriched δ13Corg signatures, as a result of high marine productivity during present oxic highstand. On the other hand, the LGM sediments are characterized by low TOC and TN contents, high TOC/TN and TS/TOC values with depleted δ13Corg signatures, characteristic of C3-derived terrestrial organic matter input during that anoxic lowstand. However, at the top of mounds at the seafloor, where gas hydrate and authigenic carbonate nodules occur, the host sediments have a mixture of both Holocene and LGM geochemical signatures. Both gas hydrate and authigenic carbonate, formed by the anaerobic oxidation of methane, increased the sedimentary volume and caused an uplift of older sediments, inducing mound formation. The thickness of the Holocene sediments over mounds is very small or absent exposing the last glacial maximum (LGM) sediments to the seafloor. The uplift of the LGM sediments within mounds is estimated to be >2 m. We conducted geochemical analysis to detect such sediment movement, using samples collected by shallow cores in the Joetsu Basin, eastern margin of the Japan Sea.

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Mooney, Christopher J., and Michael J. Kingsford. "Discriminating populations of medusae (Chironex fleckeri, Cubozoa) using statolith microchemistry." Marine and Freshwater Research 68, no. 6 (2017): 1144. http://dx.doi.org/10.1071/mf16104.

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The structure of medusae populations is poorly known. Natural geochemical signatures based on elemental composition of calcified structures are a common tool for investigating population structure or connectivity in marine systems. Chironex fleckeri (Cubozoa) medusae have a hard calcified structure, the statolith. Laser ablation–inductively coupled plasma mass spectrometry was used to determine the elemental composition of statoliths at varying spatial scales. We investigated medusae population structure using both univariate (element:Ca ratios) and multivariate (multi-element:Ca signature) analyses. Significant differences in some elemental ratios were found among regions (separated by hundreds of kilometres) and among many sites (separated by kilometres) within regions. Canonical discriminant analyses of multi-element:Ca signatures successfully distinguished between both regions and sites within regions with correct classifications of 100% of samples to some locations. Statolith microchemistry can help discriminate populations of jellyfish, but a multiseason comparison demonstrated the need to calibrate spatial differences by season. Our evidence and recent ecological data suggest that populations of C. fleckeri medusae are highly localised at spatial scales of kilometres; potential causal factors are discussed.

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Journal articles on the topic 'Geochemical signatures'

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