Economic Geology最新文献

{"title":"Boron and Oxygen Isotope Systematics of Two Hydrothermal Systems in Modern Back-Arc and Arc Crust (PACMANUS and Brothers Volcano, W-Pacific)","authors":"L. Schlicht, O. Rouxel, J. Deans, Stephen Fox, Y. Katzir, K. Kitajima, S. Kasemann, A. Meixner, W. Bach","doi":"10.5382/econgeo.4986","DOIUrl":"https://doi.org/10.5382/econgeo.4986","url":null,"abstract":"\u0000 A better characterization of subsurface processes in hydrothermal systems is key to a deeper understanding of fluid-rock interaction and ore-forming mechanisms. Vent systems in oceanic crust close to subduction zones, like at Brothers volcano and in the eastern Manus basin, are known to be especially ore rich. We measured B concentrations and isotope ratios of unaltered and altered lava that were recovered from drilling sites at Brothers volcano and Snowcap (eastern Manus basin) to test their sensitivity for changing alteration conditions with depth. In addition, for Brothers volcano, quartz-water oxygen isotope thermometry was used to constrain variations in alteration temperature with depth. All altered rocks are depleted in B compared to unaltered rocks and point to interaction with a high-temperature (>150°C) hydrothermal fluid. The δ11B values of altered rocks are variable, from slightly lower to significantly higher than those of unaltered rocks. For Brothers volcano, at the Upper Cone, we suggest a gradual evolution from a fluid- to a more rock-dominated system with increasing depth. In contrast, the downhole variations of δ11B at Snowcap as well as δ11B and δ18O variations at the NW Caldera (Site U1530) of Brothers volcano are suggested to indicate changes in water-rock ratios and, in the latter case, also temperature, with depth due to permeability contrasts between different lithology and alteration type boundaries. Furthermore, δ11B values from the NW Caldera (Site U1527) might point to a structural impact on the fluid pathway. These differences in the subseafloor fluid flow regime, which ranges from more pervasive and fluid-controlled to stronger and controlled by lithological and structural features, have significant influence on alteration conditions and may also impact metal precipitation within the sea floor.","PeriodicalId":11469,"journal":{"name":"Economic Geology","volume":"1 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2023-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87561757","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"REVIEWERS OF BOOKS","authors":"","doi":"10.5382/econgeo.2022.rev-bk","DOIUrl":"https://doi.org/10.5382/econgeo.2022.rev-bk","url":null,"abstract":"","PeriodicalId":11469,"journal":{"name":"Economic Geology","volume":"75 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136136182","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"REVIEWERS OF MANUSCRIPTS","authors":"","doi":"10.5382/econgeo.2022.rev-ms","DOIUrl":"https://doi.org/10.5382/econgeo.2022.rev-ms","url":null,"abstract":"","PeriodicalId":11469,"journal":{"name":"Economic Geology","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136136183","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Formation of Gold Deposits (Neil Phillips)","authors":"D. Craw","doi":"10.5382/econgeo.118.1.br01","DOIUrl":"https://doi.org/10.5382/econgeo.118.1.br01","url":null,"abstract":"","PeriodicalId":11469,"journal":{"name":"Economic Geology","volume":"26 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2023-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84694434","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"INTERESTING PAPERS IN OTHER JOURNALS","authors":"","doi":"10.5382/econgeo.118.1.ip01","DOIUrl":"https://doi.org/10.5382/econgeo.118.1.ip01","url":null,"abstract":"","PeriodicalId":11469,"journal":{"name":"Economic Geology","volume":"22 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2023-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88367027","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Geochronology and Mapping Constraints on the Time-Space Evolution of the Igneous and Hydrothermal Systems in the Taurus Cu-Mo District, Eastern Alaska","authors":"D. Kreiner, C. Holm-Denoma, Laura S. Pianowski, Zachary Flood, D. Stevenson, G. Graham, J. Vazquez, R. Creaser","doi":"10.5382/econgeo.4999","DOIUrl":"https://doi.org/10.5382/econgeo.4999","url":null,"abstract":"\u0000 The Taurus porphyry Cu-Mo district contains four mineralized porphyry centers in the eastern interior of Alaska. All four centers were emplaced during a magmatic episode that spanned from ca. 72 to 67 Ma, with seven distinct igneous suites. Each igneous suite resulted in hydrothermal alteration and mineralization, with younger pulses overprinting older pulses. Each magmatic-hydrothermal system is not present at all four mineralized centers. Apart from the Dennison occurrence, each mineralized center records pulses of repeated intermediate-silicic magmatism and associated alteration and mineralization.\u0000 Laser ablation-inductively coupled plasma-mass spectrometry U-Pb zircon crystallization ages indicate that an early quartz porphyry dike swarm ranges in age from ca. 71 to 70 Ma and is associated with potassic, sericitic, and propylitic alteration. Quartz latite intrusions were emplaced at ca. 69 Ma and exhibit early sodiccalcic alteration overprinted by potassic, sericitic, and propylitic alteration. The Taurus monzonite suite is cut by quartz latite but yielded an ca. 70 Ma emplacement age and exhibits the largest footprint of potassic and sericitic alteration. Feldspar porphyry dikes were emplaced ca. 69 Ma and have significant tourmaline-bearing potassic and sericitic alteration. This suite was followed by development of an igneous breccia with a monzonitic igneous matrix. Sodic-calcic alteration was associated with the igneous brecciation. A small stock of monzonite was emplaced at ca. 68 Ma causing locally pervasive sericite-tourmaline-pyrite alteration. The youngest suite of magmatism dated in the district is a series of granodiorite porphyry dikes with weak sodic-calcic and propylitic alteration that truncates earlier alteration assemblages.\u0000 Mineralization in the district consists of chalcopyrite and molybdenite associated with sugary quartz veins with potassium feldspar and biotite alteration envelopes (A veins). Less common banded quartz-molybdenite veins (B veins) occur with potassium feldspar envelopes. Gold occurs throughout the district and is strongly correlated with copper grade. Sericitic alteration contains lower copper contents and is predominantly associated with quartz-pyrite veins with sericite envelopes (D veins). Pyrrhotite and local arsenopyrite are present in sericitic assemblages. Pyrrhotite also occurs as inclusions in pyrite within D veins.\u0000 Magmas across the district exhibit oxidized characteristics, evidenced by the presence of abundant magnetite, rare titanite, and elevated Eu/Eu* and Ce/Ce* in zircon. Zircon Th/U and Yb/Gd compositions suggest a fractionation path controlled by apatite, titanite, and hornblende. Zircon rare earth element ratios and trace element data indicate two distinct batches of magma evolved from mafic parental compositions to monzonite and granodioritic compositions via fractional crystallization. In the early pulse of magma (ca. 72–69 Ma), fractional crystallization was key to ore formatio","PeriodicalId":11469,"journal":{"name":"Economic Geology","volume":"107 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2023-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88634343","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Stratiform Host-Rock Replacement via Self-Sustaining Reactions in a Clastic-Dominated (CD-Type) Zn Deposit","authors":"J. Magnall, R. Wirth, N. Hayward, S. Gleeson, A. Schreiber","doi":"10.5382/econgeo.4988","DOIUrl":"https://doi.org/10.5382/econgeo.4988","url":null,"abstract":"\u0000 Stratiform to stratabound replacement of a mixed siliciclastic-carbonate host rock is a defining characteristic of many sediment-hosted base metal deposits. Mineralized rocks in clastic-dominated (CD-type) Zn-Pb ore deposits, which represent our highest value base metal resources, are generally thin (101 m), laterally extensive (103 m), and stratiform to stratabound in fine-grained siltstone and mudstone facies. At the recently discovered Teena CD-type Zn-Pb deposit (Proterozoic Carpentaria Province, Australia), the host rock was undergoing burial diagenesis when altered and mineralized by hydrothermal fluids that moved up to 2 km lateral to the fluid input conduit (growth fault) through intraformational intervals. In much of the deposit, carbonate dissolution was an important reaction permeability control, although significant amounts of mineralization also occur in carbonate-free siliciclastic beds. In this study, transmission electron microscopy (TEM) data has been generated on a drill core sample that preserves a sharp reaction front between mineralized and unmineralized domains of the fine-grained siliciclastic compositional end member (carbonate free). Petrographic and mineralogical data provide evidence that oxidized hydrothermal fluids moved through the protolith via reaction permeability that developed from feldspar dissolution. The nature of reactive fluid flow was determined by reactions that took place at the fluid-mineral interface. Pyrite formation during the earliest stage of the hydrothermal paragenesis increased the mineral reactive surface area in the protolith. Acidity was then generated in situ via self-sustaining reactions involving pyrite oxidation, transient Fe sulfate formation, and sphalerite precipitation, which provided positive feedbacks to enhance porosity creation and further fluid infiltration and mineralization. In the absence of carbonate, however, ore fluid pH was buffered by K-feldspar dissolution (~4.5), thereby ensuring sphalerite precipitation was not inhibited under more acidic conditions. All CD-type deposits in the Carpentaria Province are hosted by a protolith comprising carbonate, K-feldspar, pyrite, and organic matter; these phases set the boundary conditions for the development of self-sustaining reactions during ore formation. Importantly, these self-sustaining reactions represent a Goldilocks zone for ore formation that is applicable to other sediment-hosted deposits that formed via replacement of mixed siliciclastic-carbonate host rocks (e.g., stratiform Cu).","PeriodicalId":11469,"journal":{"name":"Economic Geology","volume":"1 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2023-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75718289","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"INSTRUCTIONS TO AUTHORS, 2023","authors":"Gillian Harvey","doi":"10.5382/econgeo.118.1.ita01","DOIUrl":"https://doi.org/10.5382/econgeo.118.1.ita01","url":null,"abstract":"","PeriodicalId":11469,"journal":{"name":"Economic Geology","volume":"12 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2023-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78322909","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"SEG Awards for 2022: Penrose Gold Medal, Silver Medal, Waldemar Lindgren Award, Marsden Award, Brian J. Skinner Award","authors":"","doi":"10.5382/econgeo.2022.award","DOIUrl":"https://doi.org/10.5382/econgeo.2022.award","url":null,"abstract":"","PeriodicalId":11469,"journal":{"name":"Economic Geology","volume":"140 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2023-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88738849","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Sukari Gold Deposit, Egypt: Geochemical and Geochronological Constraints on the Ore Genesis and Implications for Regional Exploration","authors":"B. Zoheir, A. Holzheid, A. Zeh, R. McAleer, Mohamed El-Behairy, U. Schwarz-Schampera, T. Graupner, D. Lentz, F. Xiong","doi":"10.5382/econgeo.4990","DOIUrl":"https://doi.org/10.5382/econgeo.4990","url":null,"abstract":"\u0000 The Sukari gold deposit (>15 Moz Au) in the Eastern Desert of Egypt is hosted by a deformed granitoid stock (Sukari tonalite-trondhjemite intrusion) and mainly occurs as a network of crosscutting sulfide-bearing quartz (± carbonate) veins and intensely sulfidized-silicified-sericitized wall rock. Emplacement of the Sukari intrusion into a tectonized Neoproterozoic accretionary complex was controlled by a system of NE- to NNE-trending oblique faults that are related to a deep-seated positive flower structure. A robust genetic model has been hampered by the poorly understood relationships between gold mineralization and host rocks. In this study, zircon U-Pb ages of three samples from the Sukari intrusion define a crystallization age of ~695 ± 2 Ma. In contrast, hydrothermal sericite from the ore zone yields an 40Ar/39Ar age of ~625 ± 3 Ma, which coincides with the onset of major sinistral transpression in the region.\u0000 Features including sigmoidal morphology of gold quartz veins and abundant subhorizontal tension gashes alongside widespread brecciation and recrystallization suggest that quartz veining occurred during renewed shortening and exhumation through the brittle-ductile transition. Petrographic and micro-X-ray fluorescence (µXRF) studies indicate that disseminated gold and sulfides, commonly associated with sericite and carbonate alteration, are mostly confined to stylolitic bands in the quartz veins. Oscillatory and sector zoning patterns, irregular As-rich bands, and truncations between early- and late-genetic pyrites reflect variations in temperature and mechanism of ore deposition, demonstrated by variable As/S and Co/Ni ratios in the different pyrite generations. Laser ablation-inductively coupled plasma-mass spectrometry analysis pinpoints the covariance of gold and arsenic contents in pyrite, but free milling gold inclusions in microfractures consistently have a mercury-bearing electrum composition, depicting different ore formation stages.\u0000 Ore fluids with δ34SH2s values of –1.9 to –3.0‰, modeled from gold-associated pyrite and arsenopyrite assemblages with nearly identical δ34S values, suggest a likely single source of sulfur. Alternatively, multisourced sulfur could have extensively mixed and equilibrated by fluid reaction with carbonaceous wall rock. Gold deposition was triggered by abrupt changes in fluid pH and fO2. As an implication for future exploration, sites of maximized strain gradients adjacent to granitoid bodies along extensive transpression zones in the district could be highly prospective targets, particularly where imprinted by sericite-carbonate ± graphite alteration.","PeriodicalId":11469,"journal":{"name":"Economic Geology","volume":"28 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2022-12-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90737009","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}