{"title":"北秦岭地层(中国中部)火山岩序列变质作用中的古生代造山运动金矿化:桐柏地区银洞坡金矿床的启示","authors":"Ming-Chun Chai, Jian-Wei Li, Ya-Fei Wu, Xiao-Ping Xia, Huai-Yu He, Wei Fu","doi":"10.1007/s00126-024-01265-4","DOIUrl":null,"url":null,"abstract":"<p>Phanerozoic orogenic gold deposits worldwide are commonly considered to be formed from metamorphic devolatilization of marine carbonaceous sedimentary rocks. Here we show that the Yindongpo gold deposit from the Qinling orogen (central China) is genetically associated with the metamorphism of volcanic rocks during the late Paleozoic orogeny, which involved the closure of the Shangdan ocean. Gold mineralization at Yindongpo is hosted in lower Paleozoic metavolcanic-sedimentary sequences and occurs mainly as lenticular to stratiform ore bodies that formed in three paragenetic stages represented by quartz-ankerite-pyrite (stage I), quartz-carbonate-sulfide (stage II) and quartz-calcite assemblages (stage III), respectively. Rutile grains coexisting with auriferous pyrite from stage II yield U–Pb ages of 395 ± 9 to 400 ± 13 Ma (2σ). Fluid inclusions in quartz of stages I and II are dominated by CO<sub>2</sub>-rich (~ 10 mol%) aqueous fluids with low salinities (< 4.9 wt% NaCl equivalent) and total homogenization temperatures ranging from 241 to 352 ºC, whereas the values for H<sub>2</sub>O-rich inclusions of stage III are 0.2 to 2.6 wt% NaCl equivalent and 151 to 164 °C. Based on secondary ion mass spectrometry analysis of oxygen isotopes of quartz (Qz-1 to Qz-4), the calculated δ<sup>18</sup>O<sub>fluid</sub> values for the quartz-forming fluids are 1.3 to 7.0‰ in stage I, –3.1 to 6.6‰ in stage II, and –9.6 to –3.7‰ in stage III. These data indicate a metamorphic origin of ore fluids that underwent Rayleigh fractionation and incursion of meteoric water. The large variation in <sup>40</sup>Ar<sup>*</sup>/<sup>4</sup>He ratios (1.7–30.0), caused by accumulation of radiogenic Ar<sup>*</sup> and He loss within some pyrite samples, can be ascribed to regional metamorphism and deformation. Ore sulfides have sulfur (δ<sup>34</sup>S<sub>V-CDT</sub> = –2.1 to 3.3‰) and lead (<sup>206</sup>Pb/<sup>204</sup>Pb = 17.008–17.152, <sup>207</sup>Pb/<sup>204</sup>Pb = 15.402–15.493, and <sup>208</sup>Pb/<sup>204</sup>Pb = 38.254–38.564) isotopic compositions that are consistent with those of pyrite in the metavolcanic host rocks. Results presented here suggest that the ore fluids and, by inference, gold of the Yindongpo deposit were derived primarily from the volcanic sequences during regional metamorphism and deformation in response to the Early Devonian Qinling collisional orogeny. The Yindongpo deposit represents the first recognized Paleozoic orogenic gold deposit in the Qinling orogen, and thus has important implications for regional metallogeny and gold exploration.</p>","PeriodicalId":18682,"journal":{"name":"Mineralium Deposita","volume":null,"pages":null},"PeriodicalIF":4.4000,"publicationDate":"2024-05-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Paleozoic orogenic gold mineralization from metamorphism of volcanic sequences in the North Qinling terrane (central China): Insights from the Yindongpo gold deposit in the Tongbai area\",\"authors\":\"Ming-Chun Chai, Jian-Wei Li, Ya-Fei Wu, Xiao-Ping Xia, Huai-Yu He, Wei Fu\",\"doi\":\"10.1007/s00126-024-01265-4\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<p>Phanerozoic orogenic gold deposits worldwide are commonly considered to be formed from metamorphic devolatilization of marine carbonaceous sedimentary rocks. Here we show that the Yindongpo gold deposit from the Qinling orogen (central China) is genetically associated with the metamorphism of volcanic rocks during the late Paleozoic orogeny, which involved the closure of the Shangdan ocean. Gold mineralization at Yindongpo is hosted in lower Paleozoic metavolcanic-sedimentary sequences and occurs mainly as lenticular to stratiform ore bodies that formed in three paragenetic stages represented by quartz-ankerite-pyrite (stage I), quartz-carbonate-sulfide (stage II) and quartz-calcite assemblages (stage III), respectively. Rutile grains coexisting with auriferous pyrite from stage II yield U–Pb ages of 395 ± 9 to 400 ± 13 Ma (2σ). Fluid inclusions in quartz of stages I and II are dominated by CO<sub>2</sub>-rich (~ 10 mol%) aqueous fluids with low salinities (< 4.9 wt% NaCl equivalent) and total homogenization temperatures ranging from 241 to 352 ºC, whereas the values for H<sub>2</sub>O-rich inclusions of stage III are 0.2 to 2.6 wt% NaCl equivalent and 151 to 164 °C. Based on secondary ion mass spectrometry analysis of oxygen isotopes of quartz (Qz-1 to Qz-4), the calculated δ<sup>18</sup>O<sub>fluid</sub> values for the quartz-forming fluids are 1.3 to 7.0‰ in stage I, –3.1 to 6.6‰ in stage II, and –9.6 to –3.7‰ in stage III. These data indicate a metamorphic origin of ore fluids that underwent Rayleigh fractionation and incursion of meteoric water. The large variation in <sup>40</sup>Ar<sup>*</sup>/<sup>4</sup>He ratios (1.7–30.0), caused by accumulation of radiogenic Ar<sup>*</sup> and He loss within some pyrite samples, can be ascribed to regional metamorphism and deformation. Ore sulfides have sulfur (δ<sup>34</sup>S<sub>V-CDT</sub> = –2.1 to 3.3‰) and lead (<sup>206</sup>Pb/<sup>204</sup>Pb = 17.008–17.152, <sup>207</sup>Pb/<sup>204</sup>Pb = 15.402–15.493, and <sup>208</sup>Pb/<sup>204</sup>Pb = 38.254–38.564) isotopic compositions that are consistent with those of pyrite in the metavolcanic host rocks. Results presented here suggest that the ore fluids and, by inference, gold of the Yindongpo deposit were derived primarily from the volcanic sequences during regional metamorphism and deformation in response to the Early Devonian Qinling collisional orogeny. The Yindongpo deposit represents the first recognized Paleozoic orogenic gold deposit in the Qinling orogen, and thus has important implications for regional metallogeny and gold exploration.</p>\",\"PeriodicalId\":18682,\"journal\":{\"name\":\"Mineralium Deposita\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":4.4000,\"publicationDate\":\"2024-05-28\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Mineralium Deposita\",\"FirstCategoryId\":\"89\",\"ListUrlMain\":\"https://doi.org/10.1007/s00126-024-01265-4\",\"RegionNum\":2,\"RegionCategory\":\"地球科学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q1\",\"JCRName\":\"GEOCHEMISTRY & GEOPHYSICS\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Mineralium Deposita","FirstCategoryId":"89","ListUrlMain":"https://doi.org/10.1007/s00126-024-01265-4","RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"GEOCHEMISTRY & GEOPHYSICS","Score":null,"Total":0}
Paleozoic orogenic gold mineralization from metamorphism of volcanic sequences in the North Qinling terrane (central China): Insights from the Yindongpo gold deposit in the Tongbai area
Phanerozoic orogenic gold deposits worldwide are commonly considered to be formed from metamorphic devolatilization of marine carbonaceous sedimentary rocks. Here we show that the Yindongpo gold deposit from the Qinling orogen (central China) is genetically associated with the metamorphism of volcanic rocks during the late Paleozoic orogeny, which involved the closure of the Shangdan ocean. Gold mineralization at Yindongpo is hosted in lower Paleozoic metavolcanic-sedimentary sequences and occurs mainly as lenticular to stratiform ore bodies that formed in three paragenetic stages represented by quartz-ankerite-pyrite (stage I), quartz-carbonate-sulfide (stage II) and quartz-calcite assemblages (stage III), respectively. Rutile grains coexisting with auriferous pyrite from stage II yield U–Pb ages of 395 ± 9 to 400 ± 13 Ma (2σ). Fluid inclusions in quartz of stages I and II are dominated by CO2-rich (~ 10 mol%) aqueous fluids with low salinities (< 4.9 wt% NaCl equivalent) and total homogenization temperatures ranging from 241 to 352 ºC, whereas the values for H2O-rich inclusions of stage III are 0.2 to 2.6 wt% NaCl equivalent and 151 to 164 °C. Based on secondary ion mass spectrometry analysis of oxygen isotopes of quartz (Qz-1 to Qz-4), the calculated δ18Ofluid values for the quartz-forming fluids are 1.3 to 7.0‰ in stage I, –3.1 to 6.6‰ in stage II, and –9.6 to –3.7‰ in stage III. These data indicate a metamorphic origin of ore fluids that underwent Rayleigh fractionation and incursion of meteoric water. The large variation in 40Ar*/4He ratios (1.7–30.0), caused by accumulation of radiogenic Ar* and He loss within some pyrite samples, can be ascribed to regional metamorphism and deformation. Ore sulfides have sulfur (δ34SV-CDT = –2.1 to 3.3‰) and lead (206Pb/204Pb = 17.008–17.152, 207Pb/204Pb = 15.402–15.493, and 208Pb/204Pb = 38.254–38.564) isotopic compositions that are consistent with those of pyrite in the metavolcanic host rocks. Results presented here suggest that the ore fluids and, by inference, gold of the Yindongpo deposit were derived primarily from the volcanic sequences during regional metamorphism and deformation in response to the Early Devonian Qinling collisional orogeny. The Yindongpo deposit represents the first recognized Paleozoic orogenic gold deposit in the Qinling orogen, and thus has important implications for regional metallogeny and gold exploration.
期刊介绍:
The journal Mineralium Deposita introduces new observations, principles, and interpretations from the field of economic geology, including nonmetallic mineral deposits, experimental and applied geochemistry, with emphasis on mineral deposits. It offers short and comprehensive articles, review papers, brief original papers, scientific discussions and news, as well as reports on meetings of importance to mineral research. The emphasis is on high-quality content and form for all articles and on international coverage of subject matter.