Resource Geology最新文献

{"title":"Ore‐forming process of the Haigou gold deposit in the eastern Central Asian Orogenic Belt, NE China: Constrains from EPMA and LA‐ICP‐MS analysis of Au‐bearing pyrite","authors":"Yuan-Wei Chen, Huan Li, Chaoyang Zheng, S. M. Elatikpo, Shanlin Cheng, Wenting Jiang","doi":"10.1111/rge.12304","DOIUrl":"https://doi.org/10.1111/rge.12304","url":null,"abstract":"The Haigou lode deposit, containing 40 t of gold at an average grade of 3.5 g/t, is one of the largest deposits in the Jiapigou gold belt located along the eastern segment of the northern margin of the North China Craton. The deposit comprises 15 gold‐bearing quartz veins hosted in a Carboniferous monzonite–monzogranite stock. Although many studies relating the genesis of this deposit have been carried previously, the understanding of ore‐forming process remains controversial. In this study, we combined field geological mapping with petrography, Electron Probe Micro Analysis (EPMA) and in situ LA‐ICP‐MS analysis of gold‐bearing pyrite to provide new insight into the genesis of the gold deposit. Our results show that Au in the Haigou gold deposit mainly exists in the form of native gold. LA‐ICP‐MS in situ multi‐element mapping shows that Au has a significant positive correlation with Ag, Te, Bi and Pb in Au‐bearing pyrite, indicating that these elements co‐precipitated with Au in pyrite lattice. The ore‐forming fluid existed under medium to low temperature, aiding complexing of the gold with sulfur, chlorine, and tellurium. Decoupling of sulfide and telluride complexes facilitated gold precipitation in the Haigou area. The abundance of lead and nickel tellurides in the Haigou gold deposits with general absence of tellurium in native gold is indicative of expulsion of tellurium through boiling during the process of fluid migration and evolution. Also, coexistence of Bi in native gold indicates that they were at Au–Bi eutectic. The gold‐bearing pyrite is characterized by dispersed magnetite in and around the fractures. The Au–Te–Bi–Pb element anomalies indicate that fluid oxygen fugacity increases while sulfur fugacity decreases with time, resulting in Au precipitation. Our results provide a new theoretical basis for the establishment of metallogenic model and deep prospecting of the Haigou gold deposit.","PeriodicalId":21089,"journal":{"name":"Resource Geology","volume":"3 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89231830","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 genesis of Xindian gold deposit, Liaodong Peninsula, NE China: Constraints from zircon U–Pb ages, S–Pb isotopes, and pyrite trace element chemistry","authors":"Bing Yu, Qingdong Zeng, H. Frimmel, Jinhui Yang, Lingli Zhou, Foteini Drakou, S. Mcclenaghan, Yongbin Wang, Ruiliang Wang","doi":"10.1111/rge.12303","DOIUrl":"https://doi.org/10.1111/rge.12303","url":null,"abstract":"The Xindian deposit is a medium tonnage (>5 tonnes of Au) quartz vein‐type gold deposit located on the south‐central part of the Liaodong Peninsula, China. A total of 37 auriferous quartz veins are hosted within the Paleoproterozoic metamorphic rocks of the Gaixian Formation and Late Triassic porphyritic biotite granite. Mineral paragenesis indicates that gold mineralization took place in three stages: early milky quartz‐pyrite stage, main gray quartz‐polymetallic sulfide and gold stage, and late quartz‐calcite‐pyrite stage. Silicification and pyritization are spatially and temporally associated with the main mineralization stage. Zircon U–Pb dating from dikes that predate and postdate the mineralization constrain the timing of mineralization to the Early Cretaceous, between 127.2 and 120.9 Ma. High‐precision in‐situ S isotope analyses yielded δ34S values for pyrite, sphalerite and galena of 10.1–11.0‰, 10.3–10.5‰, and 8.6–8.8‰, respectively, indicating that S was derived from the multiple sources. In‐situ Pb isotope analyses resulted in 208Pb/204Pb, 207Pb/204Pb, and 206Pb/204Pb ratios of 38.207–38.634, 15.598–15.668, and 18.027–18.143, respectively, for pyrite and galena, suggesting Pb derivation from a mixture of Gaixian Formation metamorphic rocks and other potential sources. In‐situ LA‐ICP‐MS trace element mapping and spot analyses show that the inner core of the pyrite (Py‐ic) formed early and is generally enriched in Au, As, Co, Ni, Bi, and Te, the outer core of the pyrite (Py‐oc) contains less Co, Ni, As, and Au, but more Cu, Pb, and Zn, whereas the rim of the pyrite (Py‐r) is enriched in Ag, Sn, Sb, Cu, Pb, and Zn. Trace element signatures of pyrite reveal that the mineralizing fluid was initially of magmatic‐hydrothermal origin, and subsequently modified by intensive interaction with the wall rock (Gaixian Formation). Our results consistently demonstrate that the Xindian gold deposit is resulted from fluid–rock interaction between the Early Cretaceous magmatic‐hydrothermal fluids and Gaixian Formation metamorphic wall rocks that enriched the metal budget of the mineralizing fluid. Then the addition of meteoric water significantly changed the physical and chemical conditions of the mineralizing fluid, triggering gold precipitation in the Xindian deposit. The results of our study expand the Early Cretaceous gold metallogenic models in the Liaodong Peninsula, highlighting the importance of the Gaixian Formation for regional gold mineralization.","PeriodicalId":21089,"journal":{"name":"Resource Geology","volume":"603 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90089830","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"High‐sulfidation epithermal–porphyry transition in the Kumbokarno Prospect, Trenggalek district, East Java, Indonesia: Constraints from mineralogy, fluid inclusion, and sulfur isotope studies","authors":"F. A. Aldan, A. Idrus, R. Takahashi, Genki Kaneko","doi":"10.1111/rge.12289","DOIUrl":"https://doi.org/10.1111/rge.12289","url":null,"abstract":"An indication of high‐sulfidation epithermal–porphyry transition was observed in the Kumbokarno prospect, East Java, Indonesia. The prospect is composed of two Middle Miocene intrusions with tonalitic and dioritic compositions. Tonalite, the main host‐rock was subjected to argillic, advanced argillic, and vuggy quartz alteration, whereas the juxtaposing diorite was subjected to peripheral propylitic alteration. Three types of vein exist in the research area, which are massive quartz, comb quartz, and stockwork vein. In addition, supergene alteration represented by goethite and hematite pervasively superimposed both the hydrothermal alteration and mineralization. Fluid inclusion petrography and microthermometry analysis on three types of quartz veins distinguished primary fluid inclusions into two groups, that is, V30 group composed of vapor (30 vol%)–liquid (70 vol%), and the second group V30H group composed of vapor (30 vol%)–halite (30 vol%)–liquid (40 vol%). The homogenization temperatures of both the groups show a similar range of ca. 350–480°C, but the V30H group has significantly higher salinity (35–50 wt% NaCl eq.) compared to the V30 group (10–20 wt% NaCl eq.). In terms of the vein types, the massive quartz vein has the highest homogenization temperatures, followed by the comb quartz vein and lastly the stockwork veins. The presence of alunite and its sulfur isotope compositions, δ34S = 19.6 (σ = 2.1‰), indicate acidic pH and presence of SO42− in the hydrothermal fluids. The prospect is an intrusion‐centered magmatic‐hydrothermal system reflecting the porphyry‐epithermal transition. The fluid inclusions with high homogenization temperatures up to 480°C and high salinity up to 50 wt% NaCl eq. also support the transition of porphyry to high‐sulfidation epithermal mineralization. The presence of two different types of primary fluid inclusions suggests that boiling process occurred and separated the original magmatic fluid into the liquid and vapor phases. More, this fluid underwent dilution and mixing with meteoric waters. The migration of both the fluids were likely unrelated to the formation of the advanced argillic–argillic alteration halo because the quartz veins cut across this alteration. The prospect was later subjected to intensive weathering process that altered most of the sulfides into iron oxides and hydroxides. Small amounts of copper and minor gold were detected, especially in the iron oxides and hydroxides ones with colloform and bladed textures. The Kumbokarno prospect evidences the potential for high‐sulfidation to porphyry deposits at the Southern Mountain Arc, Indonesia.","PeriodicalId":21089,"journal":{"name":"Resource Geology","volume":"32 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80060105","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 ore‐forming fluids characteristics of quartz‐vein type scheelite deposits in eastern Yanbian, NE China: Evidence from in situ LA‐ICP‐MS rare earth elements of Yangjingou and Sidaogou deposits","authors":"Jing-mou Li, Yun‐sheng Ren, Yu-jie Hao, Qingdong Zeng","doi":"10.1111/rge.12295","DOIUrl":"https://doi.org/10.1111/rge.12295","url":null,"abstract":"The quartz‐vein type scheelite deposits distributed in the Hunchun SN‐trending gold‐copper‐tungsten belt in eastern Yanbian, Jilin Province, are a group of recent discovery for the past decade. To determine properties of the ore‐forming fluids and the mineralization mechanism, in situ laser ablation‐inductively coupled plasma‐mass spectrometry (LA‐ICP‐MS) rare earth elements (REE) analysis of the ore mineral scheelite was carried out for the selected Yangjingou and Sidaogou scheelite deposits in this metallogenic belt. The results showed that the substitution of REE3+ for Ca2+ in scheelite from the Yangjingou scheelite deposit can be accounted for the substitution mechanism: 3Ca2+ = 2REE3+ + □Ca (where □ is a site vacancy). It shows a slightly right‐dipped flat REE pattern with distinct positive Eu anomalies. The Sidaogou scheelite deposit, completes the substitution via the 2Ca2+ = REE3+ + Na+ and Ca2+ + W6+ = REE3+ + Nb5+ mechanisms. It shows left‐dipped REE pattern with relative enrichment of MREEs (mainly Dy) with negative Eu anomalies in the scheelite core and no or insignificant positive Eu anomalies in the scheelite rim. By comparing with the REE of granites which are close related to mineralization in the area, the ore‐forming fluids of these two scheelite deposits are determined to be mainly derived from magmatism. The inapparent correlation between EuN and Eu*N of the Yangjingou scheelite deposit and the high EuN/Eu*N values indicate that its ore‐forming fluids are reducing fluids. Its strong positive Eu anomalies are not entirely inherited from the mineralized tonalite, but is due to the release of Eu from the water‐rock reaction. The good correlation between EuN and Eu*N and the low EuN/Eu*N values in the Sidaogou scheelite deposit indicate that the ore‐forming fluids are oxidizing fluids. This may be caused by the mixing of the original magmatic fluid with a large amount of meteoric water. This study suggests that the water‐rock reaction is an important mineralization mechanism for the quartz vein‐type scheelite deposits in eastern Yanbian. In addition, fluid mixing is also important for the Sidaogou scheelite deposit. All these mechanisms influence the REE compositional characteristics of scheelite. The initial ore‐bearing fluids metasomatized the metamorphic rocks of Wudaogou Group, resulting in water‐rock reaction, and enriched ore‐forming materials such as Ca and W. As the ore‐forming fluids migrated upward along the NW‐trending structures, the escape of CO2 and CH4 caused by the tectonic decompression disrupted the physiochemical balance of the ore‐forming fluid system, catalyzed the combination of Ca2+ and WO42−, resulting in the precipitation and enrichment of the scheelite.","PeriodicalId":21089,"journal":{"name":"Resource Geology","volume":"3 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81387135","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Element mobility during formation of the Ruwai Zn‐Pb‐Ag skarn deposit, Central Borneo, Indonesia","authors":"C. Dana, A. Agangi, R. Takahashi, A. Idrus, Chunkit Lai, Nico A. Nainggolan","doi":"10.1111/rge.12290","DOIUrl":"https://doi.org/10.1111/rge.12290","url":null,"abstract":"The Ruwai deposit is Indonesia's largest Zn‐Pb‐Ag skarn deposit and is located in Lamandau district, Central Borneo, within the Central Borneo metallogenic belt. This skarn deposit consists of four main zones, namely Gojo, Karim, Ruwai, and Southwest Gossan Zones. The skarn orebodies are mostly hosted by limestone of the Jurassic Ketapang Complex where quartz diorite of the Cretaceous Sukadana Granitoid is the ore‐causative intrusion. Despite the several mineralogical studies carried out in this deposit, there is still a lack of knowledge of its geochemical characteristics. This study evaluates the element mobility during skarn formation on the basis of skarn and ore mineralogy combined with lithogeochemical data of the intrusions, sedimentary wall rocks, and skarn bodies. The skarn mineralogy of the Ruwai skarn complex can be divided into prograde, retrograde and supergene stages. The prograde stage is characterized by the formation of an anhydrous assemblage of garnet‐pyroxene, while the retrograde stage features the replacement of prograde minerals by predominant epidote‐chlorite‐actinolite. The mineralization was first introduced during the late prograde stage, while the formation of massive orebodies attributed to the retrograde stage. The skarn samples show a wide range of major element contents, but both the mineralized skarn and massive orebodies show similar trace and rare‐earth elements patterns in global Phanerozoic limestone‐ and upper crust sedimentary rocks‐normalized spider diagrams. The skarn and orebodies, as well as the metalimestone in this study area, are depleted in REE, although HREE are higher than LREE. Most metals (e.g., Zn, Pb, Ag, Cu, Fe) in skarn and associated orebodies, interpreted to be predominantly magmatic‐sourced, show co‐occurring enrichment or depletion relative to the metalimestone and intrusive rocks. The isocon analysis shows that there was significant mass loss as a consequence of significant volatile loss, such as CO2, during skarn formation. Major oxides and large ion lithophile elements mostly behaved as mobile elements during skarn formation, whereas rare‐earth and high field strength elements tended to be immobile. However, the occurrence of several HFSE‐ and REE‐bearing minerals in Ruwai deposit (i.e., zircon, thorite, cerite, cerianite, monazite, allanite), suggesting minor or local mobility of these elements. Such unexpected behavior can be justified by the occurrence of fluorine‐rich hydrothermal fluid, which could have been responsible for the increasing mobility of these elements.","PeriodicalId":21089,"journal":{"name":"Resource Geology","volume":"1 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79651703","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Chemical compositions of the Neogene bedded manganese deposits in the Fukaura area, Northeast Japan","authors":"K. Komuro, Takashi Ito","doi":"10.1111/rge.12299","DOIUrl":"https://doi.org/10.1111/rge.12299","url":null,"abstract":"Inorganic chemical compositions are determined for a series of ores from three bedded manganese deposits, that is, Kitaichi, Teranosawa, and Maruyama, in the Fukaura area, northeast Japan. The deposits occur as layers or lenses conformably in sedimentary or pyroclastic rocks of the Odoji formation of the Onnagawa stage in the Neogene period. The ores are composed of lower goethite ore and upper todorokite ore. The ores in the bedded manganese deposits are anomalously high in certain elements: t‐Fe2O3 (max. 51.2%), P2O5 (0.34%), As (9200 ppm), and Pb (600 ppm) in the goethite ore, and MnO (48.5%), Ba (28,000 ppm), Co (560 ppm), Mo (660 ppm), Ni (200 ppm), Tl (32 ppm), V (530 ppm), and W (520 ppm) in the todorokite ore. In the Kitaichi profile, there is distinct compositional zoning, that is, Fe‐As‐Y, P‐Pb, Cu, Co‐W‐Tl, and Mn‐Ba‐Mo‐Sr‐V, in ascending order. Based on the occurrences and chemical compositions of the Fukaura manganese deposits and the geological and paleoceanographic backgrounds, hydrothermal input or upwelling of anaerobic stratified water would be a possible source of elements of initial ferromanganese deposits. The zoning would be made by early diagenetic redistribution process of manganese from initial Fe‐Mn deposits, left residual products of goethite ore at the original horizon. Distinct compositional zoning would be made by the different adsorption behavior of goethite and todorokite for minor elements during early diagenesis.","PeriodicalId":21089,"journal":{"name":"Resource Geology","volume":"144 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76818374","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Diagenetic and epigenetic origins for Cu‐Ag mineralization in the Khoemacau Zone 5 deposit, Kalahari Copperbelt, northwestern Botswana","authors":"M. Keeditse, Yasushi Watanabe, A. Arribas, T. Echigo, Catherine Knight, Oarabile Disang, Hannah Buamono","doi":"10.1111/rge.12286","DOIUrl":"https://doi.org/10.1111/rge.12286","url":null,"abstract":"In the Kalahari Copperbelt, the mechanism of regional scale Cu‐Ag mineralization has remained intensely debated between early diagenesis and a single pass during a regional deformation event. At the Zone 5 Cu‐Ag deposit in northwestern Botswana, the orebody is hosted preferentially by chemically reduced metasedimentary rocks that overly oxidized, hematite‐bearing arkosic sandstone. An early diagenetic mineralizing event has been identified which is characterized by fine‐grained stratiform pyrite, including recrystallized framboidal pyrite, intergrown with diagenetic mineral assemblages in the host‐rock. Diagenetic pyrite is in textural equilibrium with chalcopyrite, sphalerite, galena, and (Fe‐Co‐Ni) sulfarsenide. These minerals were subsequently overprinted by a more intense, multi‐stage, structurally‐controlled hydrothermal Cu‐Ag mineralization event related to the Damaran orogeny (~600–480 Ma). The hydrothermal Cu‐Ag mineralization was deposited from hot (~236–265°C), high salinity (19–24.6 wt% NaCl equiv.) hydrothermal ore fluids. Petrographic results reveal an apparent overlap in trace metal associations (Cu, Fe, As, Zn, Pb, Ni, Co) between the two mineralizing events, which can be explained by remobilization of precursor sulfides. The major Ag‐carriers in the ore are chalcocite, covellite, and bornite. The δ34S values of diagenetic pyrite range from −35.8 to +11.4‰, whereas those of hydrothermal epigenetic sulfides, including pyrite, range from −28.0 to +3.0‰. We propose that the hydrothermal sulfides had acquired some bacterially‐reduced sulfur from earlier‐formed minerals. The δ18O and δ13C values of quartz and calcite associated with the hydrothermal mineralization are typical of Neoproterozoic sediment‐hosted Cu‐Ag deposits. However, the δ18O isotopic values of the calcite gangue are anomalously depleted, which is likely due to recrystallization under metamorphic conditions. Our studies at Zone 5 indicate that the Zone 5 Cu‐Ag deposit is the result of a multi‐stage mineralization history that includes both diagenetic and epigenetic events (punctuated by >400 m.y.) facilitated by a strong litho‐structural control.","PeriodicalId":21089,"journal":{"name":"Resource Geology","volume":"74 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74068518","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Breccia characteristics and classification of the GW orebodies, Balatoc Diatreme, Philippines: Insights to breccia facies and distribution across diatremes","authors":"Acer Jian T. Figueroa, J. Gabo‐Ratio","doi":"10.1111/rge.12282","DOIUrl":"https://doi.org/10.1111/rge.12282","url":null,"abstract":"A careful descriptive characterization of breccias, including diatremes, is useful for comparative purposes during exploration, rather than the colloquial use of various breccia terminology in ore exploration. Here, we present the first detailed breccia characterization of the Balatoc Diatreme‐hosted GW orebodies in the Acupan deposit, Philippines. Three breccia types are identified from descriptive classification of the GW orebodies. GW 3/13, located at the northwestern rim of the diatreme, is a medium‐ to coarse‐grained rotational, quartz‐cemented diorite breccia, whereas GW 11, at the eastern portion of the diatreme, is a medium‐ to coarse‐grained mosaic calcite‐cemented andesite breccia. Both GW orebodies located at the southwestern portion of the diatreme, GW 4/7 and GW 6, are medium‐ to coarse‐grained rotational quartz‐cemented polymict breccias. The breccia facies and distribution emplaced during a single event include: (a) Crackle breccias proximal to the unbrecciated host rocks. (b) Mosaic breccia facies along the contact between the surrounding host rocks and orebody. (c) Rotational breccia facies near the outline of the diatreme. At Balatoc, the mineralized GW orebodies are characterized by mosaic and rotational clast distributions, suggesting that these breccia types are priority targets in ore exploration. Recognizing these various breccia types in other deposits may serve as an exploration vector to determine their position in a diatreme‐hosted deposit.","PeriodicalId":21089,"journal":{"name":"Resource Geology","volume":"158 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76096670","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Geological, mineralogical and ore fluid characteristics of the Tagun‐Khin‐Dan gold mineralization in Mogok‐Mandalay‐Mergui Belt, Central Myanmar","authors":"Sai Pyae Sone, K. Yonezu, A. Imai, Koichiro Watanabe, T. Tindell, K. Sanematsu","doi":"10.1111/rge.12298","DOIUrl":"https://doi.org/10.1111/rge.12298","url":null,"abstract":"The Tagun‐Khin‐Dan gold deposit in the Mogok‐Mandalay‐Mergui Belt, Central Myanmar, is characterized by an array of quartz‐veins hosted in mudstone of the Kogwe Formation of the Carboniferous Mergui Group. Two major deformational stages were recorded in the area; (1) N‐S shortening and (2) uplifting and emplacement of various dykes and quartz veinlets. The N‐S shortening within the area lead the development of km‐scale faults, determined largely by the presence of a zone of major WNW‐ESE trending dextral strike‐slip faulting. Quartz veins in the deposit include: (1) type‐A quartz veins, parallel to the dextral NW‐SE trending major fault; and (2) type‐B quartz veins which occur as isolated parallel veins. Gold in the type‐A quartz vein is present as native gold and electrum locked within pyrite and associated with pyrite and galena and in the type‐B quartz veins as electrum associated with sulfide minerals such as pyrite, chalcopyrite, galena and sphalerite. The mineralization stages can be classified into the type‐A quartz vein stage and the type‐B quartz vein stage. Two type of fluid inclusions; liquid‐rich aqueous inclusions (L‐type) and vapor‐rich aqueous inclusions (V‐type) are identified in the type‐A quartz veins. The homogenization temperature of L‐type fluid inclusions of the type‐A quartz veins ranges from 203 to 321°C and salinity of the fluid inclusions varies from 0.4 to 1.6 wt% NaCl equiv. The homogenization temperature of V‐type fluid inclusions of type‐A quartz veins ranges from 290 to 340°C with a salinity ranging from 0.4 to 1.9 wt% NaCl equivalent. In the type‐B quartz veins, only liquid‐rich aqueous inclusions (L‐type) are identified. The type‐B quartz veins yielded low homogenization temperatures from 160 to 220°C, with low salinities from 0.2 to 1.9 wt% NaCl equiv. compared with those of the type‐A veins. The depth range of ore formation is estimated to be a shallow depth of less than 0.2 km based on fluid inclusion microthermometry. Fluid boiling is evident during the type‐A quartz vein stage, and fluid cooling and mixing in the later type‐B quartz vein stage. Precipitation of pyrite in the ore zone occurred as four recognized types: arsenic‐rich pyrite‐1, 2, 3 in the type‐A quartz veins and pyrite‐4 in the type‐B quartz veins. A positive relation between Au and As contents of pyrites suggests that the gold is present together with arsenic in the structure of pyrites of the type‐A quartz veins as solid solution in addition to as nanoparticle inclusions. The high Co and Ni contents of pyrites of both the type‐A and the type‐B quartz veins, with no evidence of CO2 in the system indicate that the ore‐forming fluids were epizonal magmatic‐hydrothermal fluids rather than metamorphic fluid. The hydrothermal fluids of the Tagun‐Khin‐Dan deposit were driven by faulting to form the mudstone‐hosted epithermal gold mineralization and related to continuing northwards movement of the Indian Plate that initiated the displacement on the st","PeriodicalId":21089,"journal":{"name":"Resource Geology","volume":"14 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84295592","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Chemical and short‐wave infrared characteristics of white mica associated with the Gajah Tidur porphyry copper system at the deep Grasberg Cu—Au—(Mo) deposit, Indonesia","authors":"Reza Al Furqan, Yasushi Watanabe, A. Arribas, C. Leys, T. Echigo, Rici Anggun Putri, Renanda Sevirajati","doi":"10.1111/rge.12296","DOIUrl":"https://doi.org/10.1111/rge.12296","url":null,"abstract":"The Grasberg Cu—Au—(Mo) deposit comprises the shallower Main Grasberg porphyry Cu—Au and the deeper Gajah Tidur (GT) porphyry Cu—Mo—(Au) systems. The GT porphyry preserves various types of white mica whose geochemical variations provide insights into the white mica‐dominated alteration of porphyry systems. The white mica assemblages within the GT porphyry system comprise: (1) muscovite‐anhydrite‐chlorite (MAC), (2) muscovite‐chlorite‐anhydrite (MCA), and (3) muscovite‐quartz ± pyrophyllite (MQP). These assemblages display zonation from central and deep parts of the system to its shallower and peripheral parts. The MAC alteration white micas are characterized by high Na, Fe, Ti, and V concentrations, and with short‐wave infrared Al—OH absorption wavelengths of 2203–2208 nm. The MCA white micas have higher Mg content than the other two GT white mica assemblages but similar Al—OH absorption wavelengths to the MAC white micas. The MQP alteration white micas have low Na, Fe, Mg, and Ti, but relatively high Si, Al, and F, and Al—OH absorption wavelengths are largely shorter than 2202 nm. We interpret that the high Fe and Ti content of the MAC white micas is due to inheritance of these elements from mafic minerals they replaced. The higher Fe content of these white micas explain their longer wavelength Al—OH absorption positions relative to the MQP white micas. In contrast, lower Fe content and shorter Al—OH wavelengths of the MQP white micas are caused by their higher Si and Al content, which reduces iron occupancy in the white mica crystal structure. White micas in this assemblage formed at lower temperature and probable lower pH condition that may have led to a replacement of Fe by Al. The short‐wave infrared Al—OH position of white mica together with the associated hydrothermal assemblage can be used as a proximitor for porphyry Cu hydrothermal centres. White mica associated with chlorite, anhydrite, and chalcopyrite, which commonly occur overprinting or adjacent to the potassic alteration center, are characterized by Al—OH absorption positions at 2200–2215 nm. By contrast, white mica associated with quartz‐pyrite are characterized by Al—OH wavelengths shorter than 2202 nm. In the distal part of porphyry Cu system, white micas may be associated with chlorite and have Al—OH absorption positions longer than 2204 nm.","PeriodicalId":21089,"journal":{"name":"Resource Geology","volume":"18 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84887947","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}