Journal articles: 'Geochemical alteration'

1

El-Desoky, Hatem M., Andongma W. Tende, Ahmed M. Abdel-Rahman, Antoaneta Ene, Hamdy A. Awad, Wael Fahmy, Hamada El-Awny, and Hesham M. H. Zakaly. "Hydrothermal Alteration Mapping Using Landsat 8 and ASTER Data and Geochemical Characteristics of Precambrian Rocks in the Egyptian Shield: A Case Study from Abu Ghalaga, Southeastern Desert, Egypt." Remote Sensing 14, no. 14 (July 18, 2022): 3456. http://dx.doi.org/10.3390/rs14143456.

Full text

Abstract:

This study evaluates the geological attributes of rocks within the Abu Ghalaga area using spatial, geochemical, and petrographic approaches. ASTER and Landsat imagery processed using band ratio and principal component analysis were used to map hydrothermal alterations, while a regional tectonic evaluation was based on automated extraction of lineaments from a digital elevation model. Geochemical and petrographic analyses were then employed for discrete scale evaluation of alteration patterns of rocks across the study location. Based on satellite image processing, alteration patterns across the study area are widespread, while evidence from lineament analysis suggests a dominant NW–SE tectonic trend accompanied by a less dominant ENE–WSW direction. The different rock units exposed in the studied district are arranged chronologically from oldest to youngest as arc metavolcanic group (basalt and rhyolite), arc metagabbro–diorite, gneissose granite (granodiorite and tonalite), and dykes (aplite and felsite). Various types of igneous and metamorphic rocks have propylitic, phyllic, and argillic zones. Geochemical data indicate that the studied rocks are classified into granite, granodiorite, gabbroic diorite, and gabbro. Geochemically, the rocks have a sub-alkaline magma type. The granodiorite–tonalite is derived from the calc–alkaline magma nature, while gabbro and diorite samples exhibit tholeiitic to calc–alkaline affinity. The tectonic setting of the studied rocks trends toward volcanic arc granite (VAG). Based on petrographic, geochemical, and remote analyses, sericitization, chloritization, epidotization, kaolinitization, carbonatization, and silicification are the main alteration types present in the study area. As a result of lineaments analysis, the existing fractures and structural planes form valid flow paths for mineral-bearing hydrothermal solutions.

APA, Harvard, Vancouver, ISO, and other styles

2

Planavsky, Noah J., Leslie J. Robbins, Balz S. Kamber, and Ronny Schoenberg. "Weathering, alteration and reconstructing Earth's oxygenation." Interface Focus 10, no. 4 (June 12, 2020): 20190140. http://dx.doi.org/10.1098/rsfs.2019.0140.

Full text

Abstract:

Deciphering the role—if any—that free oxygen levels played in controlling the timing and tempo of the radiation of complex life is one of the most fundamental questions in Earth and life sciences. Accurately reconstructing Earth's redox history is an essential part of tackling this question. Over the past few decades, there has been a proliferation of research employing geochemical redox proxies in an effort to tell the story of Earth's oxygenation. However, many of these studies, even those considering the same geochemical proxy systems, have led to conflicting interpretations of the timing and intensity of oxygenation events. There are two potential explanations for conflicting redox reconstructions: (i) that free oxygen levels were incredibly dynamic in both time and space or (ii) that collectively, as a community—including the authors of this article—we have frequently studied rocks affected by secondary weathering and alteration (particularly secondary oxidation) while neglecting to address the impact of this alteration on the generated data. There are now multiple case studies that have documented previously overlooked secondary alteration, resolving some of the conflicting constrains regarding redox evolution. Here, an analysis of a large shale geochemistry database reveals significant differences in cerium (Ce) anomalies, a common palaeoredox proxy, between outcrop and drill core samples. This inconsistency provides support for the idea that geochemical data from altered samples are frequently published in the peer-reviewed literature. As individuals and a geochemical community, most of us have been slow to appreciate how pervasive the problem is but there are examples of other communities that have faced and met the challenges raised by such quality control crises. Further evidence of the high potential for alteration of deep-time geochemical samples, and recognition of the manner in which this may lead to spurious results and palaeoenvironmental interpretations, indicate that sample archiving, in publicly accessible collections needs to become a prerequisite for publication of new palaeoredox data. Finally, the geochemical community need to think about ways to implement additional quality control measures to increase the fidelity of palaeoredox proxy work.

APA, Harvard, Vancouver, ISO, and other styles

3

Taylor, R. E., P. E. Hare, and T. D. White. "Geochemical criteria for thermal alteration of bone." Journal of Archaeological Science 22, no. 1 (January 1995): 115–19. http://dx.doi.org/10.1016/s0305-4403(95)80169-3.

Full text

APA, Harvard, Vancouver, ISO, and other styles

4

Bilić, Šime, and Vesnica Garašić. "PETROLOGICAL CHARACTERISTICS OF CLASTIC SEDIMENTARY ROCKS FROM THE ST. BARBARA ORE MINE IN RUDE NEAR SAMOBOR." Rudarsko-geološko-naftni zbornik 36, no. 1 (2021): 121–35. http://dx.doi.org/10.17794/rgn.2021.1.10.

Full text

Abstract:

In the scope of this research, the petrographic and geochemical analyses of clastic sedimentary rocks from the St. Barbara, copper and iron ore mine in Rude near Samobor, have been made, aiming to classify and determine the provenance and environment of formation of clastic sedimentary rocks, as well as the influence of hydrothermal fluids on their properties. Eight samples were collected in total from different locations in the mine. Six of those samples have been studied in detail. The results showed structural and geochemical variability and uneven hydrothermal alteration intensity in the samples. Based on petrographic analyses, three rocks are classified as sublithoarenite, quartz arenite and quartz greywacke. Three of the samples are classified as ore breccia, ore sandstone, and ore silt-sandstone due to the pronounced hydrothermal alterations and ore mineralisation. Comprehensively, petrographic and geochemical analyses indicate that the source rocks of the investigated clastic sedimentary rocks were felsic (La/Sc = 0.9-6.2; Th/Sc = 1.3-2.4), most probably sedimentary, possibly resedimented rocks. The extent of source rock weathering was very high (Chemical Index of Alteration CIA = 52.1 - 81.3 %) and the geotectonic position of the sedimentary basin was very likely to be at the passive continental margin.

APA, Harvard, Vancouver, ISO, and other styles

5

Mazzullo, S. J. "Geochemical and neomorphic alteration of dolomite: A review." Carbonates and Evaporites 7, no. 1 (March 1992): 21–37. http://dx.doi.org/10.1007/bf03175390.

Full text

APA, Harvard, Vancouver, ISO, and other styles

6

Lumpkin, Gregory R., and Rodney C. Ewing. "Geochemical alteration of pyrochlore group minerals; pyrochlore subgroup." American Mineralogist 80, no. 7-8 (August 1, 1995): 732–43. http://dx.doi.org/10.2138/am-1995-7-810.

Full text

APA, Harvard, Vancouver, ISO, and other styles

7

Lumpkin, Gregory R., and Rodney C. Ewing. "Geochemical alteration of pyrochlore group minerals; betafite subgroup." American Mineralogist 81, no. 9-10 (October 1, 1996): 1237–48. http://dx.doi.org/10.2138/am-1996-9-1022.

Full text

APA, Harvard, Vancouver, ISO, and other styles

8

Timkin, Timofey, Mahnaz Abedini, Mansour Ziaii, and Mohammad Reza Ghasemi. "Geochemical and Hydrothermal Alteration Patterns of the Abrisham-Rud Porphyry Copper District, Semnan Province, Iran." Minerals 12, no. 1 (January 16, 2022): 103. http://dx.doi.org/10.3390/min12010103.

Full text

Abstract:

In this study, the zonality method has been used to separate geochemical anomalies and to calculate erosional levels in the regional scale for porphyry-Cu deposit, Abrisham-Rud (Semnan province, East of Iran). In geochemical maps of multiplicative haloes, the co-existence of both the supra-ore elements and sub-ore elements local maxima implied blind mineralization in the northwest of the study area. Moreover, considering the calculated zonality indices and two previously presented geochemical models, E and NW of the study have been introduced as ZDM and BM, respectively. For comparison, the geological layer has been created by combining rock units, faults, and alterations utilizing the K-nearest neighbor (KNN) algorithm. The rock units and faults have been identified from the geological map; moreover, alterations have been detected by using remote sensing and ASTER images. In the geological layer map related to E of the study area, many parts have been detected as high potential areas; in addition, both geochemical and geological layer maps only confirmed each other at the south of this area and suggested this part as high potential mineralization. Therefore, high potential areas in the geological layer map could be related to the mineralization or not. Due to the incapability of the geological layer in identifying erosional levels, mineralogy investigation could be used to recognize this level; however, because of the high cost, mineralogy is not recommended for application on a regional scale. The findings demonstrated that the zonality method has successfully distinguished geochemical anomalies including BM and ZDM without dependent on alteration and was able to predict erosional levels. Therefore, this method is more powerful than the geological layer.

APA, Harvard, Vancouver, ISO, and other styles

9

Omotunde, V. B. "Mineralogy and Geochemistry of Hydrothermally altered Talcose rocks from Ila Orangun-Oyan areas, part of Southwestern Nigeria." Indian Journal of Science and Technology 13, no. 40 (October 31, 2020): 4244–61. http://dx.doi.org/10.17485/ijst/v13i40.1686.

Full text

Abstract:

Background/Objectives: Talcose rocks within Precambrian Basement Complex serve as relics of Archean greenstones. alterations associated with polycyclic-orogenies that affected this complex is studied to understand mineralogical and geochemical alterations. Methods: Five fresh samples of talcose rocks were collected during field mapping. These samples were cut into thin sections to reveal modal mineralogy, altered minerals and degree of alteration of such minerals. Mineral phase identification of the talcose rocks was conducted using X-ray Broker D8 ADVANCE diffractometer while whole rock analysis was carried out using Inductively Coupled Plasma Mass Spectrometry. Findings: Lithological relationship revealed from field evidence showed that the talc bodies occurred in close association with micaceous schist. The mineral assemblage of talc, tremolite, actinolite, chlorite and calcite suggest low grade greenschist metamorphic facies from possible hydrothermal alteration. Geochemical results revealed the following range of concentrations; SiO2 42.19-59.03%; Al2O3 1.1 - 11.8%; Fe2O3 7.64-9.56%; MgO 24.47-26.639%; Ni 594-1207ppm; Co 43.2-113.9ppm; Sn 6-41ppm; V 32-75ppm and Zr 1.3-58.7ppm, and these are typical of talcose rocks. Petrogenetic studies suggest a komatiitic origin with a peridotitic komatiite precursor for the talc-chlorite-tremolite schist. Enrichment in LREE, depletion in HREE and a negative Eu anomaly suggest alteration of the parent magma for the talcose rock and plagioclase fractionation. The trends observed for the LILE, HFSE and REE suggest possible contamination or mixing of crustal and mantle materials during the formation of the protolith. Ni and Co concentrations are higher than average crustal values with implication for ultrabasic to basic magma composition for the komatiitic progenitor and also suggestive of possible mineralisation. Conclusion: Mineralogical examination has revealed a talc-chlorite-tremolite composition for the talcose rocks with peridotitic komatiite precursory while geochemical composition supported ultrabasic magmatism similar to those with the Ilesha schist belt.

APA, Harvard, Vancouver, ISO, and other styles

10

Marignac, Christian, Michel Cuney, Michel Cathelineau, Andreï Lecomte, Eleonora Carocci, and Filipe Pinto. "The Panasqueira Rare Metal Granite Suites and Their Involvement in the Genesis of the World-Class Panasqueira W–Sn–Cu Vein Deposit: A Petrographic, Mineralogical, and Geochemical Study." Minerals 10, no. 6 (June 23, 2020): 562. http://dx.doi.org/10.3390/min10060562.

Full text

Abstract:

Elucidation of time-space relationships between a given wolframite deposit and the associated granites, the nature of the latter, and their alterations, is a prerequisite to establishing a genetic model. In the case of the world-class Panasqueira deposit, the problem is complicated because the associated granites are concealed and until now poorly known. The study of samples from a recent drill hole and a new gallery allowed a new approach of the Panasqueira granite system. Detailed petrographic, mineralogical, and geochemical studies were conducted, involving bulk major and trace analyses, BSE and CL imaging, EPMA, and SEM-EDS analyses of minerals. The apical part of the Pansqueira pluton consisted of a layered sequence of separate granite pulses, strongly affected by polyphase alteration. The use of pertinent geochemical diagrams (major and trace elements) facilitated the discrimination of magmatic and alteration trends. The studied samples were representative of a magmatic suite of the high-phosphorus peraluminous rare-metal granite type. The less fractionated members were porphyritic protolithionite granites (G1), the more evolved member was an albite-Li-muscovite rare metal granite (G4). Granites showed three types of alteration processes. Early muscovitisation (Ms0) affected the protolithionite in G1. Intense silicification affected the upper G4 cupola. Late muscovitisation (Fe–Li–Ms1) was pervasive in all facies, more intense in the G4 cupola, where quartz replacement yielded quartz-muscovite (pseudo-greisen) and muscovite only (episyenite) rocks. These alterations were prone to yield rare metals to the coeval quartz-wolframite veins.

APA, Harvard, Vancouver, ISO, and other styles

11

Lucas, F. A., and T. J. Fregene. "Geochemical Maturity and Paleo-Weathering Indices of Sedimentary Succession in JV Field Greater Ughelli Depo-Belt Niger Delta Basin." Journal of Applied Sciences and Environmental Management 25, no. 5 (October 26, 2021): 773–77. http://dx.doi.org/10.4314/jasem.v25i5.12.

Full text

Abstract:

This study evaluates the geochemical maturity and paleo weathering indices of X well JV-Field, Greater UghelliDepo belt Niger Delta Basin, using reflected light microscope and geochemical proxies. The data obtained identified three lithofacies units as Sand, Shale, and Shaly sand facies .The application of source area weathering using Chemical index of alteration (CIA) and Chemical index of weathering (CIW) values for the sampled intervals ranges from (48.6-94.9%) and (60.6-96.7%), and have median values of (83.2 and 90.3) % respectively which is an indication of high weathering at the source. The values are variable and it may be as a result of multiple provenances of the sediments which have variable proportions of source area weathering and related processes or may be due to low concentrations of the alkalis and alkaline earth elements. However, all the samples excluding one with depth (12430ft) show CIA and CIW values greater than 70% indicating high (intensive) weathering either at the source or during transportation before deposition .From the high alteration indices value recorded from the sampled intervals, it can be inferred that the sediments are geochemically and texturally mature.

APA, Harvard, Vancouver, ISO, and other styles

12

Simon-Astier, S. "Geochemical Constraints on the Alteration Processes of Building Materials." Mineralogical Magazine 62A, no. 3 (1998): 1407–8. http://dx.doi.org/10.1180/minmag.1998.62a.3.71.

Full text

APA, Harvard, Vancouver, ISO, and other styles

13

Poitrasson, Franck, Simon Chenery, and David J. Bland. "Contrasted monazite hydrothermal alteration mechanisms and their geochemical implications." Earth and Planetary Science Letters 145, no. 1-4 (December 1996): 79–96. http://dx.doi.org/10.1016/s0012-821x(96)00193-8.

Full text

APA, Harvard, Vancouver, ISO, and other styles

14

Schaffie, M., and M. Ranjbar. "Geochemical alteration of crude oils during thermal recovery processes." Journal of Petroleum Science and Engineering 26, no. 1-4 (May 2000): 57–65. http://dx.doi.org/10.1016/s0920-4105(00)00021-8.

Full text

APA, Harvard, Vancouver, ISO, and other styles

15

Machek, Matěj, Zuzana Roxerová, Vojtěch Janoušek, Martin Staněk, Eduard Petrovský, and Miloš René. "Petrophysical and geochemical constraints on alteration processes in granites." Studia Geophysica et Geodaetica 57, no. 4 (October 2013): 710–40. http://dx.doi.org/10.1007/s11200-013-0923-6.

Full text

APA, Harvard, Vancouver, ISO, and other styles

16

Celenk, Omer, Ramon A. L. Flores, and Alfonso P. dela Cruz. "Geochemical characterization of epithermal alteration in Southeast Negros, Philippines." Journal of Geochemical Exploration 27, no. 1-2 (October 1987): 189–211. http://dx.doi.org/10.1016/0375-6742(87)90011-2.

Full text

APA, Harvard, Vancouver, ISO, and other styles

17

Naing Oo, Toe, Lucas Donny Setijadji, I. Wayan Warmada, and Than Than Oo. "Geochemistry, Hydrothermal alteration and Ore mineralogy of Skarn Mineralization at Wethey-Pheshey area, Thabeikkyin Township, Mandalay Region, Myanmar." Journal of Applied Geology 1, no. 2 (July 26, 2016): 53. http://dx.doi.org/10.22146/jag.26961.

Full text

Abstract:

Wethey-Pheshy area is located 80 km north of Mandalay at Thabeikkyin Township, Mandalay Region. X-ray Diffraction (XRD) Analysis and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) were applied in this study. Geochemical studies on the host rocks indicate that major and minor oxides compositions of metamorphicrocks show some degree of variation. CaO, MgO, FeO, TiO2 and P2O5 concentration of the metamorphic rock samples show a coherent negative correlation with SiO2 whereas Na2O is positively correlated with SiO2. The metamorphic rocks are strongly enriched in light rare earth elements (LREE) and relatively depleted in heavy rare earth element (HREE). The depleted Eu-nomalies in the chondrite-normalized REE diagrams indicate a plagioclase-depleted Eu crustal source or fractionation during magmatic differentiation. Intrusion of granitic rocks in the diopside marble caused the base metal ore mineralization and associated skarn alterations. Granite shows the sub-alkaline nature and peraluminous character. It is identified as I-type granite (magnetite series) developed in the volcanic arc setting. Hydrothermal alteration types associated with gold and skarn mineralization in the study area include calc-silicate alteration, propylitization, sericitization (argillitization) and hematization. Based on the nature and characteristics of host rocks, mineralization and alteration style and geochemical characteristics in the study area is identified as intrusion-related skarn mineralization. Common ore minerals include chalcopyrite, galena, sphalerite, pyrite, gold and Fe-oxides.

APA, Harvard, Vancouver, ISO, and other styles

18

Hidayatullah, Muhammad Shofi, Agus Didit Haryanto, Johanes Hutabarat, and Ryan Hidayat. "etermination of Geothermal Reservoir Zone of Sorik Marapi, Mandailing Natal, North Sumatra." Indonesian Association of Geologists Journal 1, no. 1 (March 31, 2021): 13–24. http://dx.doi.org/10.51835/iagij.2021.1.1.24.

Full text

Abstract:

The Sorik Marapi Geothermal Power (SMGP) Field is located in Mandailing Natal (350 km to the southeast from Medan), North Sumatra. This study needed alteration mineral data validation with fluid geochemical characteristics from surface manifestations, and production wells were determined the geothermal reservoir zone. Therefore geothermometer and geoindicator calculations were used. Laboratory tests were carried out on 38 surface manifestations and 11 cutting samples of exploration well. Manifestations in this area include hot springs, fumaroles, and steaming ground. Alteration minerals found in the study area are anhydrite, epidote, calcite,chlorite, muscovite, pyrophyllite, and zeolite. The alteration zone is located in the zeolite zone, the epidote zone,and the anhydrite-sericite zone. Geochemical manifestations of surface and production wells containing chloride water, sulfate water, sulfate-chloride water, and bicarbonate water. The estimated reservoir temperature of SH-01 well shows temperatures ranging from 240–280˚C, SH-02 well shows temperatures of 249.89–302.92˚C, SH-03 well show temperatures of 231.09–280˚C. The mineral geothermometer calculation, which is correlated with the geochemical fluid geothermometer, shows valid results. This is evident from the estimated reservoir temperatures of the two geothermometers.

APA, Harvard, Vancouver, ISO, and other styles

19

Zar, Aung Tay, I. Wayan Warmada, Lucas Donny Setijadji, and Koichiro Watanabe. "Geochemical Characteristics of Metamorphic Rock-Hosted Gold Deposit At Onzon-Kanbani Area, Central Myanmar." Journal of Geoscience, Engineering, Environment, and Technology 2, no. 3 (September 1, 2017): 191. http://dx.doi.org/10.24273/jgeet.2017.2.3.410.

Full text

Abstract:

Gold and associated base metal mineralization of Onzon-Kabani area located in the western border of generally N-S trending Mogoke Metamorphic Belt where well-known Sagaing fault is served as a western boundary of this area. In this research area, many artisanal and small-scale gold mines were noted in last three decades. Gold mineralization is hosted in marble and gneiss unit of research area but most common in marble unit. Variety of igneous intrusions are also observed in research area. Mineralizations are observed as fissure filling veins as well as lesser amount of disseminated nature in marble unit. Mineralogically, gold are associated with other base metal such as pyrite, galena, sphalerite, chalcopyrite, marcasite and arsenopyrite. Hydrothermal alteration halos are developed in peripheral of hydrothermal conduits or mineralization veins from proximal to distal such as 1) silicic, 2) sericite-illite, and 3) propylitic alteration. Most of hydrothermal minerals from each altered zones showed that near neutral condition of pH (e.g. adularia, calcite, illite, sericite and chlorite). Alternatively, hydrothermal alteration zones that show with ore minerals such as native gold, electrum, sphalerite, galena, chalcopyrite, arsenopyrite and marcasite which mostly observed in silicic alteration zone. Typical boiling characters of vein textures and fluid inclusion petrography are observed in hydrothermal system of research area. Boiling, cooling and mixing are possiblily responsible for gold deposition in hydrothermal system. In this paper, authors are documented to clarify the type of mineralization based on hydrothermal alterations, ore and gangue mineral assemblages and fluid inclusion study. All of these data can describe and play an important role for both with respect to understanding deposit genesis and in mineral exploration.

APA, Harvard, Vancouver, ISO, and other styles

20

Vezzoni, Simone, Diego Pieruccioni, Yuri Galanti, Cristian Biagioni, and Andrea Dini. "Permian Hydrothermal Alteration Preserved in Polymetamorphic Basement and Constraints for Ore-genesis (Alpi Apuane, Italy)." Geosciences 10, no. 10 (October 5, 2020): 399. http://dx.doi.org/10.3390/geosciences10100399.

Full text

Abstract:

The reconstruction of the polymetamorphic history of basement rocks in orogens is crucial for deciphering past geodynamic evolution. However, the current petrographic features are usually interpreted as the results of the metamorphic recrystallization of primary sedimentary and/or magmatic features. In contrast, metamorphic rocks derived by protoliths affected by pre-metamorphic hydrothermal alterations are rarely recognized. This work reports textural, mineralogical and geochemical data of metasedimentary and metaigneous rocks from the Paleozoic succession of the Sant’Anna tectonic window (Alpi Apuane, Tuscany, Italy). These rocks were recrystallized and reworked during the Alpine tectono-metamorphic event, but the bulk composition and some refractory minerals (e.g., tourmaline) are largely preserved. Our data show that the Paleozoic rocks from the Alpi Apuane were locally altered by hydrothermal fluids prior to Alpine metamorphism, and that the Permian magmatic cycle was likely responsible for this hydrothermal alteration. Finally, the Ishikawa Alteration Index, initially developed for magmatic rocks, was applied to metasedimentary rocks, providing a useful geochemical tool for unravelling the hydrothermal history of Paleozoic rocks, as well as a potential guide to the localization of hidden ore deposits in metamorphic terranes.

APA, Harvard, Vancouver, ISO, and other styles

21

Adams, Cameron, Michael Dentith, and Marco Fiorentini. "Characterization of altered mafic and ultramafic rocks using portable XRF geochemistry and portable Vis-NIR spectrometry." Geochemistry: Exploration, Environment, Analysis 21, no. 2 (February 15, 2021): geochem2020–065. http://dx.doi.org/10.1144/geochem2020-065.

Full text

Abstract:

The accurate characterization of mafic and ultramafic rocks is a challenging but necessary task given the spatial and genetic relationship of mineralization with specific lithologies (e.g. komatiite hosted nickel-sulfides preferentially associated with cumulate-rich ultramafic rocks). Rock classification is further complicated as most mafic and ultramafic rocks have undergone varying degrees of alteration. The accuracy and reproducibility of characterization can be significantly improved by using portable energy dispersive X-ray fluorescence (pXRF) chemical data with portable visible and near-infrared (pVis-NIR) mineralogical data.A new workflow using pXRF and pVis-NIR is presented and used to reliably characterize mafic and ultramafic rocks from the Yilgarn Craton, Western Australia. The workflow involves six steps:(1) Mitigate and identify compound processing and closure issues. For example, we used a pXRF with helium flush to reliably and rapidly measure light elements and mitigate closure, i.e. problems related to data failing to sum to 100%.(2) Identify and exclude geochemically heterogeneous samples. Heterogeneity may be unrelated to alteration and caused by veining or small-scale structure interleaving of different rock types. Geochemical heterogeneity was evaluated using skewness and kurtosis of SiO2 data.(3) Relate rocks from similar magmatic, weathering and alteration events. This was achieved by interpreting data grouping of Vis-NIR ferric and ferrous iron data via a 852 nm/982 nm reflectance v. 651 nm/982 nm reflectance plot and the ferrous abundance index. Unrepresentative data were omitted.(4) Correct XRF iron data, and characterize lithology and alteration. Values ascribed to regions in the TAS (total alkali silica) diagram were used to approximate FeO and Fe2O3. Subsequently, geochemical indices (e.g. Mg#) were used to characterize the alteration box plot.(5) Characterize fractionation in detail. Fractionation variation diagrams were used to interpret fractionation, e.g. MgO v. Al2O3, Ca/Al v. Al2O3, Ni/Cr v. Ni/Ti, and MgO v. Cr.(6) Identify and quantify talc alteration and serpentinization. This included the use of a new alteration plot (Mg# v. 1410 nmRAD/Albedo) to estimate serpentinization and identify relationships between serpentine, carbonate, chlorite and talc abundances.The results and observations contained in this contribution have important implications for progressive technologies such as core logging platforms that are equipped with pXRF and pVis-NIR instruments.

APA, Harvard, Vancouver, ISO, and other styles

22

YILDIRIM, Demet Kıran, Zeynep DONER, and Ali Tugcan UNLUER. "Strategic Element Enrichments in Hallaçlar Volcanites (Bayramiç, Çanakkale)." Afyon Kocatepe University Journal of Sciences and Engineering 22, no. 5 (October 27, 2022): 1184–92. http://dx.doi.org/10.35414/akufemubid.1124737.

Full text

Abstract:

In this study, Hallaçlar Volcanites located in Bayramiç-Çanakkale region were evaluated in terms of strategic element contents. Mineralogical-petrographical and geochemical investigations were carried out on the samples which were taken from the outcrops with intense hydrothermal alteration. The stratigraphy of the study area consists of the Sütüven Formation (Kazdağı Metamorfites), Çetmi Ophiolitic Melange, Evciler Pluton and Hallaçlar Volcanites. The intensity of hydrothermal alterations gradually increases in Hallaçlar Volcanites towards to the ophiolitic rocks and the Evciler Pluton. As a result of the geochemical analyzes carried out, it was observed that the yttrium (Y), zirconium (Zr), thorium (Th), tin (Sn) and antimony (Sb) elements were enriched in the Hallaçlar volcanites. It can be concluded that these elements were enriched in the volcanites with the hydrothermal solutions leaching from the elder metamorphic rocks.

APA, Harvard, Vancouver, ISO, and other styles

23

Bordeaux-Rego, Fabio, Jose Adriano Ferreira, Claudio Alberto Salinas Tejerina, and Kamy Sepehrnoori. "Modeling Oil Recovery in Brazilian Carbonate Rock by Engineered Water Injection Using Numerical Simulation." Energies 14, no. 11 (May 24, 2021): 3043. http://dx.doi.org/10.3390/en14113043.

Full text

Abstract:

Waterflooding remains the most commonly used method to improve oil recovery. Although the injected brine type is mainly dependent on its availability, few of its characteristics can be controlled during project design. Published laboratory work indicates that the adjustment of injected brine composition can cause an increase in oil production by wettability alteration. This research objective is to propose a novel four-step framework for modeling improved oil recovery by Engineered Water Injection from laboratory to numerical simulation for carbonate formations. We use a geochemical-based model that estimates contact angles to predict wettability alteration. The steps are (1) screening criteria, (2) geochemical evaluation, (3) wettability alteration modeling, and (4) coreflood history-match. We validate our framework by conducting history-match simulations of Brazilian Pre-Salt corefloods. Incremental oil recovery factors are between 5 to 11%, consistent with those reported during experiments. The reduction in residual oil saturation varied from 3 to 5%. This work is a new systematic procedure to model oil recovery using a comprehensive approach that is fundamental to understanding the underlying wettability alteration mechanisms by Engineered Water Injection.

APA, Harvard, Vancouver, ISO, and other styles

24

Honarpazhouh, Jamal, Ali Asghar Hassanipak, and Kumars Seifpanahi Shabani. "Integration of Stream Sediment Geochemical and Aster Data for Porphyry Copper Deposit Exploration in Khatun Abad, North West of Iran / Integracja geochemicznych danych o osadach dennych oraz danych pozyskanych z systemu aster do poszukiwań geologicznych w rejonie złóż miedzi porfirytowej w khatun abad, w północno-zachodniej części iranu." Archives of Mining Sciences 58, no. 1 (March 1, 2013): 37–54. http://dx.doi.org/10.2478/amsc-2013-0003.

Full text

Abstract:

Urumieh-Dokhtar magmatic belt is the host of large porphyry copper deposits in Iran. Khatun Abad area is located in north west part of this belt, so in this study, the stream sediment geochemical survey and hydrothermal alteration zones extracted from ASTER data were used to generation new target for future lithogeochemical survey. In this study after a brief discussion on descriptive statistics, principal component analysis (PCA) and hierarchical cluster analysis were used to compress the information to a few maps and to assist in determining multi-element associations. Then C-A fractal method was used for map classification. In order to extraction hydrothermal zones ASTER data were used. ASTER SWIR bands are most useful for the identification of alteration minerals such as Alunite, Pyrophylite, Kaolinite, Sericute and Carbonates. In this paper based on spectral analysis of ASTER SWIR data six maps of alteration zones were prepared. Geochemical study and spectral analysis of ASTER data showed that mineralization and alteration are limited to E1lb and gr lithological units and have NW-SE trends from east of Khatun Abad to Ghezeljeh-Gheshlaghi.

APA, Harvard, Vancouver, ISO, and other styles

25

Fahy, William D., Elena C. Maters, Rona Giese Miranda, Michael P. Adams, Leif G. Jahn, Ryan C. Sullivan, and Benjamin J. Murray. "Volcanic ash ice nucleation activity is variably reduced by aging in water and sulfuric acid: the effects of leaching, dissolution, and precipitation." Environmental Science: Atmospheres 2, no. 1 (2022): 85–99. http://dx.doi.org/10.1039/d1ea00071c.

Full text

APA, Harvard, Vancouver, ISO, and other styles

26

Cloutier, Jonathan, and Stephen J. Piercey. "Tracing Mineralogy and Alteration Intensity Using the Spectral Alteration Index and Depth Ratios at the Northwest Zone of the Lemarchant Volcanogenic Massive Sulfide Deposit, Newfoundland, Canada." Economic Geology 115, no. 5 (August 1, 2020): 1055–78. http://dx.doi.org/10.5382/econgeo.4723.

Full text

Abstract:

Abstract The use of hyperspectral reflectance in mineral exploration has been steadily increasing in recent decades. This study presents a novel approach that integrates geochemical and spectral proxies to delineate ore formation and alteration processes, which provide new spectral-based exploration parameters that can be used in real time. The precious metal-bearing, bimodal-felsic Northwest zone of the Lemarchant volcanogenic massive sulfide (VMS) deposits, Newfoundland, Canada, is used as a case study. Alteration associated with the Northwest zone includes intense and localized sulfide (pyrite, chalcopyrite, sphalerite, and galena) and barite enrichment, as well as quartz, white mica, and chlorite alteration. Zones of elevated Zn (>5,000 ppm) are associated with high chlorite carbonate pyrite index (CCPI), Ishikawa alteration index (AI), Ba/Sr, and low Na2O values and elevated SiO2 and K2O, Fe2O3, Na2O, and BaO contents, similar to global alteration signatures in VMS deposits. Mineralized areas contain phengitic white micas with 2,200-nm absorption features longer than 2,215 nm and Mg-rich chlorites with 2,250-nm absorption features shorter than 2,252 nm. Together, these data are consistent with the Northwest zone having undergone intense hydrothermal alteration during the mineralization event. A new lithology-normalized spectral alteration index (SAI) for white mica and chlorite was developed in order to map and characterize the alteration intensity surrounding the deposit. In addition, depth ratio parameters (2200D/2340D vs. 2250D/2340D) were used to characterize mineralogical changes and zonation. Together, these features document a paleofluid pathway with Mg chlorite alteration extending to at least 300 m away from the mineralization, outside the study area, within the andesitic and dacitic units. The use of hyperspectral reflectance coupled with geochemical alteration proxies permitted the identification of areas of intense alteration, the chemical affinities of the minerals, and their relationships to alteration processes (i.e., seawater alteration versus silicification), which would not be possible using geochemistry alone.

APA, Harvard, Vancouver, ISO, and other styles

27

Halley, Scott, John H. Dilles, and Richard M. Tosdal. "Footprints: Hydrothermal Alteration and Geochemical Dispersion Around Porphyry Copper Deposits." SEG Discovery, no. 100 (January 1, 2015): 1–17. http://dx.doi.org/10.5382/segnews.2015-100.fea.

Full text

Abstract:

ABSTRACT Whole-rock lithogeochemical analyses combined with short-wave infrared (SWIR) spectroscopy provide a rapid and cost-effective method for prospecting for porphyry-type hydrothermal systems. Lithogeochemistry detects trace metals to average crustal abundance levels and allows vectoring via gradients of chalcophile and lithophile elements transported by magmatic-hydrothermal ore and external circulating fluids that are dispersed and trapped in altered rocks. Of particular use are alkalis in sericite and metals such as Mo, W, Se, Te, Bi, As, and Sb, which form stable oxides that remain in weathered rocks and soils. SWIR mapping of shifts in the 2,200-nm Al-OH absorption feature in sericite define paleofluid pH gradients useful for vectoring toward the center of the buoyant metal-bearing magmatic-hydrothermal plume.

APA, Harvard, Vancouver, ISO, and other styles

28

Lottermoser, B. G. "Alteration of Noble Metal Geochemical Cycles due to Sewage Disposal." Mineralogical Magazine 58A, no. 2 (1994): 533–34. http://dx.doi.org/10.1180/minmag.1994.58a.2.15.

Full text

APA, Harvard, Vancouver, ISO, and other styles

29

Kim, Eui-Jun, Young-Kook Hong, and Se-Jung Chi. "Geochemical Variation of Hwangsan Volcanic Complex by Large Hydrothermal Alteration." Economic and Environmental Geology 44, no. 2 (April 28, 2011): 95–107. http://dx.doi.org/10.9719/eeg.2011.44.2.095.

Full text

APA, Harvard, Vancouver, ISO, and other styles

30

Knowles, Emily, Hubert Staudigel, and Alexis Templeton. "Geochemical characterization of tubular alteration features in subseafloor basalt glass." Earth and Planetary Science Letters 374 (July 2013): 239–50. http://dx.doi.org/10.1016/j.epsl.2013.05.012.

Full text

APA, Harvard, Vancouver, ISO, and other styles

31

Whyte, J. B., and I. Nichol. "Geochemical alteration associated with the Selbaie copper-zinc-silver deposit." Journal of Geochemical Exploration 28, no. 1-3 (June 1987): 165–82. http://dx.doi.org/10.1016/0375-6742(87)90046-x.

Full text

APA, Harvard, Vancouver, ISO, and other styles

32

Fantle, Matthew S., B. Davis Barnes, and Kimberly V. Lau. "The Role of Diagenesis in Shaping the Geochemistry of the Marine Carbonate Record." Annual Review of Earth and Planetary Sciences 48, no. 1 (May 30, 2020): 549–83. http://dx.doi.org/10.1146/annurev-earth-073019-060021.

Full text

Abstract:

Carbonate sediments and rocks are valuable archives of Earth's past whose geochemical compositions inform our understanding of Earth's surface evolution. Yet carbonates are also reactive minerals and often undergo compositional alteration between the time of deposition and sampling and analysis. These changes may be mineralogical, structural, and/or chemical, and they are broadly referred to as diagenesis. Building on work over the past 40 years, we present an overview of key carbonate diagenesis terminology and a process-based framework for evaluating the geochemical impacts of carbonate diagenesis; we also highlight recent experimental and field observations that suggest metal isotopes as valuable diagenetic indicators. Our primary objectives are to demonstrate the value of coupling quantitative and analytical approaches, specifically with regard to metal isotopes and Mg/Ca, and to focus attention on key avenues for future work, including the role of authigenesis in impacting global geochemical cycles and the isotopic composition of the rock record. ▪ Quantitative frameworks utilizing well-understood diagenetic indicators and basic geochemical parameters allow us to assess the extent of diagenetic alteration in carbonate sediments. ▪ The reactivity, duration of reaction, and degree of isotopic or elemental/chemical disequilibrium determine the extent to which carbonates may be altered. ▪ Metal isotopic ratios (δ44Ca, δ26Mg, 87Sr/86Sr) can be used to constrain the extent and rate of carbonate recrystallization. ▪ Diagenetic signals may be globally synchronous, while diagenetic fluxes may impact global geochemical cycles.

APA, Harvard, Vancouver, ISO, and other styles

33

Schmitt, Jean-Michel, Sabine Huet-Taillanter, and Médard Thiry. "The industrial waste land of Mortagne-du-Nord (59) – II – Oxidizing alteration of the slags, hydrochemistry, geochemical modelling and remediation proposal." Bulletin de la Société Géologique de France 173, no. 4 (July 1, 2002): 383–93. http://dx.doi.org/10.2113/173.4.383.

Full text

Abstract:

Abstract The slag backfills of the former sulfuric acid factory of Mortagne-du-Nord (59) are sulfide- and metal-rich (Zn, Pb, Cd). Sulfide oxidation leads to acidification of surficial groundwater and the dispersal of the metals into the environment, by flow towards the rivers which run along the site. The surficial groundwater pHs fall between 2.5 and 6.8 and the metal content is very high, reaching in places 6 000 mg/L of Zn, 2.5 mg/L of Pb and 600 mg/L of Cd. To conceive a remediation scenario, we tried beforehand to understand the phenomena that govern the oxidation of the sulfides. For this purpose, water levels and water compositions have been surveyed every 2 months during 4 years, a geochemical simulation of the alteration/oxidation has been proposed and leaching tests have been performed. The survey of the water table level and periodical chemical analyses of the groundwater have shown that the slag alteration is reactivated when the water table drops until the sulfide-bearing ≪ fresh ≫ slags are unsaturated. The analysed waters always show an unbalanced negative ionic charge. Geochemical calculations allow to propose several equilibrium models of the waters and to conclude that the presence of thiosulfates (S2O23−) in the original waters most likely explains the observed ionic disequilibrium. The geochemical modelling of the slag alteration, first by percolation in unsaturated conditions (allowing O2 supply) and then under saturated conditions (without O2 renewal), reproduces satisfactorily the chemistry of sampled groundwaters. Leaching tests of the slags have been performed in the laboratory both by percolation (unsatured environment) and by cirulation (saturated and closed environment). These tests allowed to obtain alteration solutions comparable to the waters sampled on site, with progressive ≪ aging ≫ of the material, in agreement with the decrease of the dissolved metals observed on site during the 4-year survey. Moreover, the tests confirm the importance of the oxygen supply in the reactivation of the alteration. The evolution of the groundwater chemistry, the thermodynamic modelling, as well as the leaching experiments allow to determine with some details the alteration/oxidation mechanism and show that: (1) alteration is actived or reactived after a drop of the water table within the sulfide-bearing facies, (2) the oxygen supply by diffusion in the poral air is the driving force of slag oxidation, and (3) maintaining the backfills in saturated conditions practically stops alteration. The geochemical evolution of the site is directly related to its history, with successive re-profiling of the channels which have lead to a lowering of the water table of about 2 m. The remediation should be focused on in-situ processing (water treatment aimed to lower acidity, active barriers, …) rather than on ex-situ (excavation) solutions.

APA, Harvard, Vancouver, ISO, and other styles

34

Galán-Abellán, Ana-Belén, José F. Barrenechea, Raúl de La Horra, Jacinto Alonso-Azcárate, Javier F. Luque, Violeta Borruel-Abadía, and José López-Gómez. "Geochemical markers of paleoenvironments, weathering, and provenance in Permian–Triassic terrestrial sediments." Journal of Sedimentary Research 90, no. 8 (August 19, 2020): 906–20. http://dx.doi.org/10.2110/jsr.2020.44.

Full text

Abstract:

ABSTRACT This study compares several geochemical factors (major and minor rare earth elements, Ti/Al ratios, and chemical index of alteration, CIA, values) in the Early Triassic Cañizar Formation (Fm) (Buntsandtein facies) of E Iberia with those of adjacent Middle Permian and Middle Triassic units (Alcotas and Eslida fms, respectively). According to significant differences detected, it seems that most geochemical perturbation occurred during the Early Triassic. Variations in Ti/Al ratios suggest changes in source areas between the studied units and even within the Cañizar Fm. These provenance changes correlate with successive tectonic pulses during the opening and development of the Iberian Basin, as they can be linked to major sedimentary surfaces and unconformities, as well as major sedimentological variations. Ti enrichment in the lower and middle part of the Cañizar Fm, together with high Sr and P concentrations, may be indicative of environmental alterations related to acid meteoric waters. Moreover, this acid alteration took place under arid conditions as reflected by CIA values, indicating that during the deposition of the Cañizar Fm, variable but predominantly physical weathering prevailed in contrast to the chemical weathering that took place when the Alcotas and Eslida formations were deposited. Our data along with the known fossil record of the study area indicate that during the Middle–Late Permian and Early Triassic, conditions in this tectonically active area changed from humid to arid-acid, hampering biotic recovery. Then, during late Early–Middle Triassic times, the return of more humid and less acid environments promoted biotic development. Geochemical markers emerged as useful tools complementary to sedimentological, paleontological, and tectonic data for unveiling paleoenvironmental events, especially in a setting of significant regional change.

APA, Harvard, Vancouver, ISO, and other styles

35

Hendrayana, Heru, Hnin Thandar Phyu, I. Gde Budi Indrawan, and Toshitaka Kamai. "Mineralogical, Geochemical, and Mechanical Characteristics of Intrusive Andesite Rock Slope in Sangon 2 Area, Kulon Progo Regency, Indonesia." Journal of Applied Geology 5, no. 1 (August 11, 2020): 25. http://dx.doi.org/10.22146/jag.56345.

Full text

Abstract:

This study was carried out to investigate mineralogical, geochemical, and mechanical characteristics of intrusive igneous rock andesite consisting of Sangon 2 Slope located in Kulon Progo Mountains. Mineralogical characteristics of the rocks consisting of the slope were identified by visual observation of hand specimens in the field and petrographic and X-ray Diffraction (XRD) analyses of the rock samples in the laboratory, which rock genetic classification was determined. Types of rock hydrothermal alterations were determined by the presence of key minerals identified in the petrographic and XRD analyses. Hydrothermal alteration intensity was determined by comparing the number of secondary minerals to the primary minerals observed in the petrographic analyses of thin sections by point counting method. Rock weathering degrees were determined in the field based on the visual characteristics and in the laboratory-based on the Chemical Index of Alteration (CIA) of the rock samples. The rock uniaxial compressive strength (UCS) was determined by point load and compression tests. The results showed that the rocks typically consisted of 6.37 to 74.3% plagioclase, 1.52 to 6.82% quartz, 7.81 to 17.2% hornblende, and 4.81% pyroxene minerals and, therefore, were classified as andesite. The presence of chlorite and calcite as secondary minerals in the andesite rock samples indicated that the parent andesite rocks had undergone prophylactic hydrothermal alteration. Meanwhile, the percentages of primary minerals to secondary minerals indicated that the andesite rocks had undergone weak to high alteration intensity. Based on the visual characteristics, the research area consisted of fresh, slightly, moderately, highly, and completely weathered andesite rocks, and residual soil. The CIA values of the rock samples increased with the increase in rock weathering degree. Rock weathering degrees identified by the visual characteristics appeared to be in good agreement with those classified based on the CIA. The lower part of the mine slope profile consisted of fresh and slightly and moderately weathered andesite rocks, which had relatively high strength and were classified as very strong rocks. Meanwhile, the upper part of the slope profile consisted of highly and completely weathered andesite rocks, which had low compressive strength.Keywords: andesite, hydrothermal alteration, kulon progo, prophylactic alteration, weathering

APA, Harvard, Vancouver, ISO, and other styles

36

Shives, Robert B. K., B. W. Charbonneau, and K. L. Ford. "The detection of potassic alteration by gamma‐ray spectrometry—Recognition of alteration related to mineralization." GEOPHYSICS 65, no. 6 (November 2000): 2001–11. http://dx.doi.org/10.1190/1.1444884.

Full text

Abstract:

Canadian case histories document the use of airborne and ground gamma‐ray spectrometry to detect and map potassium alteration associated with different styles of mineralization. These include: volcanic‐hosted massive sulfides (Cu‐Pb‐Zn), Pilley’s Island, Newfoundland; polymetallic, magmatic‐hydrothermal deposits (Au‐Co‐Cu‐Bi‐W‐As), Lou Lake, Northwest Territories; and porphyry Cu‐Au‐(Mo) deposits at Mt. Milligan, British Columbia and Casino, Yukon Territory. Mineralization in two of these areas was discovered using airborne gamma‐ray spectrometry. In each case history, alteration produces potassium anomalies that can be distinguished from normal lithologic potassium variations by characteristic lows in eTh/K ratios. Interpretations incorporating airborne and ground spectrometry, surficial and bedrock geochemistry and petrology show that gamma‐ray spectrometric patterns provide powerful guides to mineralization. This information complements magnetic, electromagnetic, geological, and conventional geochemical data commonly gathered during mineral exploration programs.

APA, Harvard, Vancouver, ISO, and other styles

37

Li, Ruihong, Ntwali Albert, Menghe Yun, Yinsheng Meng, and Hao Du. "Geological and Geochemical Characteristics of the Archean Basement-Hosted Gold Deposit in Pinglidian, Jiaodong Peninsula, Eastern China: Constraints on Auriferous Quartz-Vein Exploration." Minerals 9, no. 1 (January 21, 2019): 62. http://dx.doi.org/10.3390/min9010062.

Full text

Abstract:

The gold deposits that are hosted in the Archean metamorphic rock, have yet to be explored beyond Pinglidian gold deposit in the northwestern Jiaodong Peninsula, eastern China. This kind of gold deposit differs from those that are hosted in Mesozoic granitoids, showing good potential for the prospecting of auriferous quartz-vein gold deposits controlled by the structures in greenfield Archean metamorphic rock. Pinglidian gold deposit is located in the hanging wall of the Jiaojia fault and consists of eight separated orebodies that are enveloped by altered rock in Archean biotite plagiogneiss. These orebodies and wall-rock alterations are strongly controlled by local structures that formed during the Mesozoic rotation and kink folding of the foliated and fissile Archean basement host. The major wall-rock alterations comprise sericitization, silicification, pyritization, and carbonation, which is up to 18 m in width and progressively increases in intensity towards the auriferous quartz vein. The visible gold is present as discrete native gold and electrum grains, which have basically filled in all manner of fractures or are adjacent to galena. We recognize two types of gold bearing quartz veins that are associated with mineral paragenetic sequences during hydrothermal alteration in the Pinglidian gold deposit. The petrological features and geochemical compositions in the reaction fronts of the alteration zone suggest variations in the physicochemical conditions during ore formation. These minerals in the wall rock, such as plagioclase, biotite, zircon, titanite, and magnetite, have been broken down to hydrothermal albite, sericite, and quartz in a K–Na–Al–Si–O–H system, and sulfides in a Fe–S–O–H system. The major and trace elements were calculated by the mass-balance method, showing gains during early alteration and losses during late alteration. The contents of K2O, Na2O, CaO, and LOI varied within the K–Na–Al–Si–O–H system during alteration, while Fe2O3 and MgO were relatively stable. Rare-earth elements (REE) changed from gains to losses alongside the breakdown of accessory minerals, such as large ion lithophile elements (LILE). The Sr and Ba contents exhibited high mobility during sericite-quartz alteration. Most of the low-mobility high-field strength elements (HFSE) were moderately depleted, except for Pb, which was extremely high in anomalous samples. The behavior of trans-transition elements (TRTE) was related to complicated sulfides in the Fe–S–O–H system and was constrained by the parameters of the mineral assemblages and geochemical compositions, temperature, pressure, pH, and fO2. These factors during ore formation that were associated with the extents and intensity of sulfide alteration and gold precipitation can be utilized to evaluate the potential size and scale of an ore-forming hydrothermal system, and is an effective exploration tool for widespread auriferous quartz veins in Archean metamorphic basements.

APA, Harvard, Vancouver, ISO, and other styles

38

Gros, Katarzyna, Ewa Słaby, Petras Jokubauskas, Jiří Sláma, and Gabriela Kozub-Budzyń. "Allanite Geochemical Response to Hydrothermal Alteration by Alkaline, Low-Temperature Fluids." Minerals 10, no. 5 (April 28, 2020): 392. http://dx.doi.org/10.3390/min10050392.

Full text

Abstract:

Allanite is one of the main rare earth elements (REE)-rich accessory minerals in composite dykes from the granitoid pluton of Karkonosze. These dykes differ in composition from the bulk of the pluton by elevated rare earth elements (REE), Y, Zr, and alkali contents, suggesting contribution of an additional component. Allanite exhibits complex alteration textures, which can be divided into two stages. The first stage is represented by allanite mantles, formed by fluid infiltration into previously crystallized magmatic allanite. These zones have low totals, are Ca-, Al-, Mg-, and light REE (LREE)-depleted, and Y-, heavy REE (HREE)-, Th-, Ti-, and alkali-enriched. The fractionation between LREE and HREE was caused by different mobility of complexes formed by these elements in aqueous fluids. The second stage includes recrystallized LREE-poor, Y-HREE-rich allanite with variable Ca, Al, Mg, and REE-fluorocarbonates. The alteration products from both stages demonstrate higher Fe3+/(Fe2+ + Fe3+) ratios and a negative Ce anomaly. These features point to the alkaline, low-temperature, and oxidized nature of the fluids. The differences in mobility and solubility of respective ligands show that the fluids from the first stage may have been dominated by Cl, whereas those of the second stage may have been dominated by F and CO2 (and PO4 in case of one sample). The inferred chemistry of the fluids resembles the overall geochemical signature of the composite dykes, indicating a major contribution of the hydrothermal processes to their geochemical evolution.

APA, Harvard, Vancouver, ISO, and other styles

39

Lavrič, Jošt V., Joerg E. Spangenberg, and Bojan Režun. "Organic geochemical records of hydrotermal alteration at Idrija mercury deposit, Slovenia." Geologija 46, no. 1 (June 30, 2003): 129–34. http://dx.doi.org/10.5474/geologija.2003.013.

Full text

APA, Harvard, Vancouver, ISO, and other styles

40

Vieillard, P., and F. Rassineux. "Thermodynamic and geochemical modelling of the alteration of two cement matrices." Applied Geochemistry 7 (January 1992): 125–36. http://dx.doi.org/10.1016/s0883-2927(09)80068-1.

Full text

APA, Harvard, Vancouver, ISO, and other styles

41

Gysi, Alexander P., and Andri Stefánsson. "Experiments and geochemical modeling of CO2 sequestration during hydrothermal basalt alteration." Chemical Geology 306-307 (May 2012): 10–28. http://dx.doi.org/10.1016/j.chemgeo.2012.02.016.

Full text

APA, Harvard, Vancouver, ISO, and other styles

42

Lacassie, Juan Pablo, Francisco Herve, and Barry Roser. "Sedimentary provenance study of the post-Early Permian to pre-Early Cretaceous metasedimentary Duque de York Complex, Chile." Andean Geology 33, no. 2 (June 30, 2010): 199. http://dx.doi.org/10.5027/andgeov33n2-a01.

Full text

Abstract:

The Duque de York Complex constitutes a post-Early Permian to pre-Early Cretaceous metasedimentary succession that crops out at the Madre de Dios and Diego de Almagro archipelagos along the Chilean Patagonian Andes. The petrography and geochemistry of sandstones and mudstones of this complex have been analyzed to characterize its source and depositional tectonic regime. Sandstone modal compositions are dominated by feldspar and, in similar but smaller proportions, by quartz. The mineralogical composition of the sandstones and mudstones is compatible with a low-grade sub-greenschist facies metamorphism. This did not affect significantly the geochemical compositions of these rocks. Nevertheless, the geochemical analyses reveal variable K+ enrichment, especially in the mudstones. Chemical Index of Alteration values of the sandstones and mudstones range between 58 and 71, indicating that the sediment underwent moderate chemical alteration in the source area or during transportation. Sandstone modal compositions are consistent with erosion of the plutonic roots of a magmatic arc. Geochemical provenance indices suggest a relatively evolved source, close in composition to typical continental magmatic arc granodiorite. Deposition of the detritus is most likely to have occurred within an active continental margin. Geochronological, petrographic, and geochemical similarities between the metasediments of the Duke de York Complex, the LeMay Group (Western Antarctica) and the Permian-Late Triassic Rakaia terrane (New Zealand) suggest a common geodynamic set-up for these three successions. This likely constituted an extensive late Paleozoic-early Mesozoic active continental margin, possibly along the Antarctic sector of Gondwana.

APA, Harvard, Vancouver, ISO, and other styles

43

Lampropoulou, Paraskevi, Petros Petrounias, Panagiota Giannakopoulou, Aikaterini Rogkala, Nikolaos Koukouzas, Basilios Tsikouras, and Konstantin Hatzipanagiotou. "The Effect of Chemical Composition of Ultramafic and Mafic Aggregates on Their Physicomechanical Properties as well as on the Produced Concrete Strength." Minerals 10, no. 5 (April 30, 2020): 406. http://dx.doi.org/10.3390/min10050406.

Full text

Abstract:

This study examines how the chemical composition of ultramafic and mafic rocks effects their physicomechanical properties and therefore how influences the concrete strength of the produced concrete specimens. For this scope, ultramafic (Group I) and mafic rocks (Group II) derived from the Veria–Naousa and Edessa ophiolite complexes (Greece) were selected in order to identify their chemical composition and their engineering properties according to international standards. Additionally, representative rocks were used as concrete aggregates in order to produce concrete specimens, whereas their mechanical strength was calculated. A geochemical index (Ga) was proposed and correlated with the engineering properties of the examined rocks as well as with the widely used alteration degree LOI (loss on ignition). Correlation diagrams between engineering properties and the proposed geochemical index (Ga) have showed that these properties were strongly influenced by the alteration processes expressed via Ga index. More particularly, mainly serpentine in ultramafic and chlorite in mafic rocks, minerals indicators for the alteration of ultramafic and mafic rocks, respectively, seem to determine their engineering properties. Concerning the mechanical strength of the produced concrete specimens, the results have showed that the increasing values of Ga index negatively effect concrete strength.

APA, Harvard, Vancouver, ISO, and other styles

44

Chen, Jiao Jiao, Ying Shu Li, Da Qing He, Dong Ming Yang, and Yi Ke Zhang. "Geochemical Anomaly Characteristics of the Soil Secondary Halo of Pangjiagou Gold Polymetallic Deposit in Chengde, Hebei Province." Advanced Materials Research 807-809 (September 2013): 2129–32. http://dx.doi.org/10.4028/www.scientific.net/amr.807-809.2129.

Full text

Abstract:

Pangjiagou gold polymetallic deposit is located in bending parts of the north east direction of the Yanshan arc structural belt in Hebei province, which has a good regional metallogenic background. According to the collection of samples and tests of eight elements for the samples of the mining area, we studied the geochemical anomaly characteristics of the soil secondary halos of the ore deposit. By means of researching on geochemical characteristics of the ore deposit, it worked out that the ore deposit possesses the characteristics of multiphase ore-forming hydrothermal activity, which is divided into the Sb-Zn mineralization period and Cu-Au mineralization period. The important prospecting of the ore deposits in the area consist of the surface oxidation, the wall rock alteration and the geochemical characteristics.

APA, Harvard, Vancouver, ISO, and other styles

45

Donatelle, A., and M. Velbel. "Geochemical characteristics of rare earth element movement during incipient alteration of pyroxenes in Guatemalan corestones." Mineralogical Magazine 72, no. 1 (February 2008): 37. http://dx.doi.org/10.1180/minmag.2008.072.1.37.

Full text

Abstract:

AbstractEarth scientists currently use changes in major and minor elements as an indication of rock alteration. Work on spheroidal weathering has shown an increase in the rare earth element (REE) whole-rock abundancescan accompany minor changes in major elementsand highlights the need for new, more sensitive, geochemical techniques of detecting incipient alteration. Augites from the core and rind of a corestone system from the Tecuamburro complex in SE Guatemala are examined to determine their role in the whole-rock REE increases.

APA, Harvard, Vancouver, ISO, and other styles

46

Újvári, Gábor, Andrea Varga, and Zsuzsanna Balogh-Brunstad. "Origin, weathering, and geochemical composition of loess in southwestern Hungary." Quaternary Research 69, no. 03 (May 2008): 421–37. http://dx.doi.org/10.1016/j.yqres.2008.02.001.

Full text

Abstract:

Loess geochemistry generally reflects paleo-weathering conditions and it can be used to determine the average composition of the upper continental crust (UCC). In this study, major and trace element concentrations were analyzed on loess samples from southwestern Hungary to determine the factors influencing their chemical compositions and to propose new average loess compositions. All studied loess samples had nearly uniform chemical composition, suggesting similar alteration history of these deposits. Chemical Index of Alteration values (58–69) suggested a weak to moderate degree of weathering in a felsic source area. Typical non-steady state weathering conditions were shown on the Al2O3–CaO+Na2O–K2O patterns, indicating active tectonism of the Alpine–Carpathian system during the Pleistocene. Whole-rock element budgets were controlled by heavy minerals derived from a felsic magmatic or reworked sedimentary provenance. Geochemical parameters indicated that dust particles must have been recycled and well homogenized during fluvial and eolian transport processes.

APA, Harvard, Vancouver, ISO, and other styles

47

Pearson, D. Graham, Jon Woodhead, and Philip E. Janney. "Kimberlites as Geochemical Probes of Earth’s Mantle." Elements 15, no. 6 (December 1, 2019): 387–92. http://dx.doi.org/10.2138/gselements.15.6.387.

Full text

Abstract:

Kimberlites are ultrabasic, Si-undersaturated, low Al, low Na rocks rich in CO2 and H2O. The distinctive geochemical character of kimberlite is strongly influenced by the nature of the local underlying lithospheric mantle. Despite this, incompatible trace element ratios and radiogenic isotope characteristics of kimberlites, filtered for the effects of crustal contamination and alteration, closely resemble rocks derived from the deeper, more primitive, convecting mantle. This suggests that the ultimate magma source is sub-lithospheric. Although the composition of primitive kimberlite melt remains unresolved, kimberlites are likely derived from the convecting mantle, with possible source regions ranging from just below the lithosphere, through the transition zone, to the core–mantle boundary.

APA, Harvard, Vancouver, ISO, and other styles

48

Bariteau, Anne, and Medard Thiry. "Analyse et simulation des transferts geochimiques au sein d'un aquifere; la nappe de Beauce et l'alteration des Sables de Fontainebleau." Bulletin de la Société Géologique de France 172, no. 3 (May 1, 2001): 367–81. http://dx.doi.org/10.2113/172.3.367.

Full text

Abstract:

Abstract Ground-water mineralisation results mainly from alteration of the confining aquifer along its flow path. Such alteration may deeply alter the aquifer formations and have to be recognized to avoid misinterpretation of the altered facies. The Beauce ground-water and the Fontainebleau Sands aquifer have been studied to highlight such ground-water/aquifer interactions. The Beauce ground-water is contained in thick limestone series (Oligo-Miocene) interlayered with the Fontainebleau Sands (Stampian). The sands show various facies related to the geomorphology: dark and reduced facies are restricted to the bottom of the formation in the center of the plateaux, oxidized yellowish facies occur in the vadose zone beneath the plateaux, and bleached white facies at the edge of the plateaux. These facies result from modern alternations due to the ground-water and the recharge waters. The water and rock chemistry allows to investigate the diverse stages of the geochemical and weathering processes that occur within the aquifer, and to calculate accurate mass balance of the dissolved and exported elements. Hydrochemistry of the Beauce ground-water: Each compartment of the aquifer can be characterised by one type of water. (1) The aquifer is recharged by two types of water. The waters coming from the limestone plateau are calco-carbonaceous, oxygenated and lightly mineralised, especially in silica; those coming from the sandy soils near the outcropping sand area are more acidic, oxygenated and very lightly mineralised. (2) The ground-water of the limestone aquifer are oxygenated, oversaturated with respect to quartz and near equilibrium with calcite and cristobalite. Silica comes from the alteration of the clay minerals and/or the cherts in the limestones. The ground-waters are of calco-carbonaceous type, have pH values approx 6.5. They are characterised by a relative low mineralisation (average 460 mg.kg (super -1) ), an oversaturation with respect to quartz and the presence of dissolved oxygen (Eh around +450 mV). (3) The ground-water of the dark sands aquifer contains hydrogen sulfur and is oxygen free (Eh around +140 mV), with relatively high Fe and SO 4 contents related to the pyrite oxidation. It is also characterised by a relatively high SiO 2 and cations contents resulting from the alteration of the alumino-silicates. (4) The ground-water of the bleached sands aquifer is strongly diluted by the recharge waters from the sandy soils. It remains oversaturated with respect to quartz and has the ability to hydrolyse the alumino-silicates. Geochemical modelling: The ground-water/aquifer interactions have been modelled. The modelisation takes into account the kinetics of water/rock interactions and was done by successive steps. (1) Alteration of the dark sands by the ground-water leads to dissolution of the pyrite and the calcite. The pyrite oxidation and the "buffering" calcite dissolution directly depend on oxygen availability in the ground-water. Muscovite remains stable, feldspars and glauconite are partially dissolved and Al-smectite forms. The composition of the resulting simulated oxydized sands agrees with the analyses. (2) The leaching of these oxydized sands by the calco-carbonaceous recharge water leads to simulate leached sands of similar composition than the unsaturated sands beneath the plateau. Muscovite remains stable; smectite, kaolinite and hematite form. (3) The final leaching of the former leached sand by the acidic recharge water brings about to simulate bleached sand. The muscovite stability, smectite dissolution and kaolinite precipitation are in conformity with the composition of the white sands. Nevertheless, the modelisation is not fully in agreement with the mass balance calculations. The discrepancy mainly comes from the simulation of excessive amounts of clay minerals and iron oxides. This precipitation excess may be related to the fact that the precipitation kinetics and/or of the organic complexations have not been taken into account in the model. Even if there is discrepancy in the mass balance, the thermokinetic simulations validate the reaction path which leads to the Beauce ground-water mineralisation and the Fontainebleau Sands bleaching. Discussion: Ground-water chemistry thus provides information on the alteration processes and indicates that the alterations are presently active. The white facies results from the progressive alteration of dark primary sands. This bleaching leads to a complete change of the geochemical characteristics of the Fontainebleau Sands. These alterations come with the export of a large amount of material corresponding to a geochemical lowering of the Beauce Plateau of at least 10 m during the Plio-Quaternary period. This example illustrates the importance of the sub-surface alterations due to ground-water flow, that are difficult to gauge from outcrop observation only.

APA, Harvard, Vancouver, ISO, and other styles

49

Macdonald, R., B. Bagiński, P. M. Kartashov, and D. Zozulya. "Behaviour of ThSiO4 during hydrothermal alteration of raremetal rich lithologies from peralkaline rocks." Mineralogical Magazine 81, no. 4 (August 2017): 873–93. http://dx.doi.org/10.1180/minmag.2016.080.138.

Full text

Abstract:

AbstractThe behaviour of ThSiO4 during low-temperature alteration has significance for element mobility and redistribution. Here we describe five types of alteration of ThSiO4 by hydrothermal fluids: (1) primary ThSiO4 associated with chevkinite-(Ce) in a quartz-epidote metasomatite; (2) during alteration of monazite-(Ce) in a quartzolite; (3) during alteration of fergusonite-(Y) in a quartz-epidote metasomatite; (4) following exsolution from chevkinite-(Ce); and (5) associated with cerite-(Ce) and with ilmenite and bastnäsite-(Ce) in late-stage veinlets in a syenitic pegmatite and a metasomatite. The great majority of crystals have been strongly altered compositionally, with variable degrees of replacement of formula elements by non-formula elements, such as Ca, Fe, P and REE. The most reliable geochemical indicators of hydrothermal alteration are low analytical totals and non-stoichiometric structural formulae. The alteration is variably ascribed to dissolution-reprecipitation and pervasive fluid infiltration along cracks. Thorium appears to have shown limited mobility in these samples.

APA, Harvard, Vancouver, ISO, and other styles

50

Conte, Aida Maria, Letizia Di Bella, Michela Ingrassia, Cristina Perinelli, and Eleonora Martorelli. "Alteration and Mineralization Products of the Zannone Giant Pockmark (Zannone Hydrothermal Field, Central Tyrrhenian Sea)." Minerals 10, no. 7 (June 27, 2020): 581. http://dx.doi.org/10.3390/min10070581.

Full text

Abstract:

The Zannone Giant Pockmark (ZGP) is a shallow-water (<−150 m) giant depression located on the shelf off Zannone Island (Pontine Archipelago, central Tyrrhenian Sea, Italy), hosting active hydrothermal vents. The ZGP seabed displays different fluid-venting morphologies (pockmarks, lithified pavements, mounds, and cone-shaped structures) and widespread bacterial communities. In this study, we analyzed ROV (Remote Operated Vehicle) images to gain information on seabed geology and the textural, mineralogical, and geochemical composition of authigenic crusts and gravel-sized clasts sampled close to active emissions. ROV images show authigenic dome-shaped crusts composed of native sulfur associated with barite, gypsum, amorphous silica, and secondary hydrothermal minerals (illite–montmorillonite). The gravel-sized clasts are mostly rhyolites strongly affected by hydrothermal alteration (Alteration Index > 88; depletion of some mobile elements and enrichment of some base metals), causing feldspar-destruction, silicification, formation of hydrothermal phyllosilicates, and precipitation of disseminated pyrite. More intense alteration implying the complete obliteration of the primary mineralogy or fabric is represented by quartz-pyrite samples. ZGP seabed morphology and petro-geochemical features of deposits point to the possible occurrence of a sulfide system linked to the degassing of magma similar to that feeding the Pleistocene products of Ponza Island.

APA, Harvard, Vancouver, ISO, and other styles

Journal articles on the topic 'Geochemical alteration'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles