The remobilization,migration,precipitation,and enrichment of ore-forming elements are closely related to structures.Therefore,detailed regional and ore-field structural analyses are critical for determining the genesi...The remobilization,migration,precipitation,and enrichment of ore-forming elements are closely related to structures.Therefore,detailed regional and ore-field structural analyses are critical for determining the genesis of a mineral deposit.The Jiangnan Orogenic Belt(JOB)is an important gold polymetallic metallogenic belt in South China,which is characterized by multiple periods of gold mineralization in the Paleozoic and Mesozoic.However,the genesis of these gold polymetallic deposits is still not well understood due to a lack of systematic research on the regional geology,ore-controlling structures and metallogenic mechanism.In this study,a detailed structural survey at the surface and in the subsurface tunnels was conducted on the Woxi Au-Sb-W deposit,the genesis of which is relatively controversial among the gold polymetallic deposits in the JOB due to poor structural constraints.In addition,a wolframite U-Pb dating was carried out to further constrain the relationship between structures and mineralization.Based on the results of these studies,together with those from previous studies,it is proposed that the Woxi deposit and surrounding areas likely underwent six periods of regional deformation,which are constrained in time and geodynamic setting.Furthermore,we present a systematic discussion on the roles of ore-controlling structures in the transportation,distribution,and deposition of ore-forming elements and localization of orebodies.According to the wolframite dating results,structural analyses,and previous data,we propose that the Woxi Au-Sb-W deposit was formed in two stages during the Yanshanian:a W(wolframite)-Au mineralization stage at ca.140 Ma and an Au-Sb-W(scheelite)mineralization stage at<130 Ma.These mineralizing events are interpreted to have a tight relationship with tectonic reactivation,and the ore-forming fluids were derived from deep sources,including those of magmatic or metamorphic origins.The Woxi deposit can therefore be classified as an“intracontinental reactivation-type”,and the mineralization is related to lithospheric extension caused by plate retreat,retention,and delamination following the cessation of westward subduction of the Paleo-Pacific Plate beneath the East Asian continent.展开更多
通过对湖南沃溪Au-Sb-W矿床鱼儿山-红岩溪矿段中黑钨矿族矿物的野外观察表明，含黑钨矿族矿物的矿石主要呈条带状、细脉状，次为浸染状构造，结构上主要为半自形-它形板状和柱状；X射线粉晶衍射结果得出其物相为钨铁矿，晶胞参数为a0：4...通过对湖南沃溪Au-Sb-W矿床鱼儿山-红岩溪矿段中黑钨矿族矿物的野外观察表明，含黑钨矿族矿物的矿石主要呈条带状、细脉状，次为浸染状构造，结构上主要为半自形-它形板状和柱状；X射线粉晶衍射结果得出其物相为钨铁矿，晶胞参数为a0：4.7454 A ，b0：5.7160A ，c0：4.9753 A ，β：90°13′；电子探针分析结果显示，MnO含量范围0.97%-11%，FeO含量范围13.65%-23.36%，WO3含量范围71.39%-76.87%，既有高MnO含量亦有低MnO含量的钨铁矿，成连续性变化，并从深部中段向浅部中段，MnO含量具有增大趋势。计算其晶体化学式为（Fe0.57-1.02Mn0.46-0.04）W0.98-1.00O4。相关分析得出FeO与MnO相关系数为-0.98，WO3与MnO相关系数为0.47，WO3与FeO相关系数为-4.10。黑钨矿族矿物中Nb和Ta的含量较低，暗示了沃溪Au-Sb-W矿床可能为沉积-改造热液成因。展开更多
The formation of many hydrothermal gold deposits is closely related to iron-rich rocks. The host rocks of the Madiyi Formation of the Mid-to Late Neoproterozoic Banxi Group for the Woxi Au(-Sb-W) deposit, which is loc...The formation of many hydrothermal gold deposits is closely related to iron-rich rocks. The host rocks of the Madiyi Formation of the Mid-to Late Neoproterozoic Banxi Group for the Woxi Au(-Sb-W) deposit, which is located in western Hunan Province of the western Jiangnan Orogen, South China, is rich in hematite, which provides a good example for studying the relationship between the formation of gold deposit and iron-rich rocks. Field investigation and petrographic observation on the unaltered, weakly altered and strongly altered rocks demonstrate that the bleaching is caused by a combination of carbonatization, sulfidation and sericitization. Mass balance calculation suggests that, during decolourization there is no change in TFe_(2)O_(3), while FeO is gained and Fe_(2)O_(3)is lost. Geochemical modeling found that Au was mainly present as AuHS(aq) and Au(HS)-2, and that the water-rock interactions decreased the sulfur fugacity which destroyed the stability of such aqueous complexes. Combined with the locally occurred native gold in quartz veins, it is concluded that the major gold precipitation mechanisms are sulfidation and fluid boiling. Based on previous geochronological and geochemical research further gold mineralization is proposed to be generated by deep sourced magmatic or metamorphic fluid migrated upward along the Woxi fault, and the iron-rich Madiyi Formation is the idea chemical trap for gold deposition. The decrease of sulfur contents caused by fluid-rock interactions and fluid boiling are the major mechanisms for gold mineralization.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.41930428)the Scientific Research Project of the Hunan Academy of Geology(Grant No.2019-17).
文摘The remobilization,migration,precipitation,and enrichment of ore-forming elements are closely related to structures.Therefore,detailed regional and ore-field structural analyses are critical for determining the genesis of a mineral deposit.The Jiangnan Orogenic Belt(JOB)is an important gold polymetallic metallogenic belt in South China,which is characterized by multiple periods of gold mineralization in the Paleozoic and Mesozoic.However,the genesis of these gold polymetallic deposits is still not well understood due to a lack of systematic research on the regional geology,ore-controlling structures and metallogenic mechanism.In this study,a detailed structural survey at the surface and in the subsurface tunnels was conducted on the Woxi Au-Sb-W deposit,the genesis of which is relatively controversial among the gold polymetallic deposits in the JOB due to poor structural constraints.In addition,a wolframite U-Pb dating was carried out to further constrain the relationship between structures and mineralization.Based on the results of these studies,together with those from previous studies,it is proposed that the Woxi deposit and surrounding areas likely underwent six periods of regional deformation,which are constrained in time and geodynamic setting.Furthermore,we present a systematic discussion on the roles of ore-controlling structures in the transportation,distribution,and deposition of ore-forming elements and localization of orebodies.According to the wolframite dating results,structural analyses,and previous data,we propose that the Woxi Au-Sb-W deposit was formed in two stages during the Yanshanian:a W(wolframite)-Au mineralization stage at ca.140 Ma and an Au-Sb-W(scheelite)mineralization stage at<130 Ma.These mineralizing events are interpreted to have a tight relationship with tectonic reactivation,and the ore-forming fluids were derived from deep sources,including those of magmatic or metamorphic origins.The Woxi deposit can therefore be classified as an“intracontinental reactivation-type”,and the mineralization is related to lithospheric extension caused by plate retreat,retention,and delamination following the cessation of westward subduction of the Paleo-Pacific Plate beneath the East Asian continent.
文摘通过对湖南沃溪Au-Sb-W矿床鱼儿山-红岩溪矿段中黑钨矿族矿物的野外观察表明，含黑钨矿族矿物的矿石主要呈条带状、细脉状，次为浸染状构造，结构上主要为半自形-它形板状和柱状；X射线粉晶衍射结果得出其物相为钨铁矿，晶胞参数为a0：4.7454 A ，b0：5.7160A ，c0：4.9753 A ，β：90°13′；电子探针分析结果显示，MnO含量范围0.97%-11%，FeO含量范围13.65%-23.36%，WO3含量范围71.39%-76.87%，既有高MnO含量亦有低MnO含量的钨铁矿，成连续性变化，并从深部中段向浅部中段，MnO含量具有增大趋势。计算其晶体化学式为（Fe0.57-1.02Mn0.46-0.04）W0.98-1.00O4。相关分析得出FeO与MnO相关系数为-0.98，WO3与MnO相关系数为0.47，WO3与FeO相关系数为-4.10。黑钨矿族矿物中Nb和Ta的含量较低，暗示了沃溪Au-Sb-W矿床可能为沉积-改造热液成因。
基金supported by the National Natural Science Foundation of China (No.41930428)the scientific research start-up fund for doctors of East China University of Technology (No.DHBK2019066)the science and technology research project of Jiangxi Education Department (No.GJJ2200754)。
文摘The formation of many hydrothermal gold deposits is closely related to iron-rich rocks. The host rocks of the Madiyi Formation of the Mid-to Late Neoproterozoic Banxi Group for the Woxi Au(-Sb-W) deposit, which is located in western Hunan Province of the western Jiangnan Orogen, South China, is rich in hematite, which provides a good example for studying the relationship between the formation of gold deposit and iron-rich rocks. Field investigation and petrographic observation on the unaltered, weakly altered and strongly altered rocks demonstrate that the bleaching is caused by a combination of carbonatization, sulfidation and sericitization. Mass balance calculation suggests that, during decolourization there is no change in TFe_(2)O_(3), while FeO is gained and Fe_(2)O_(3)is lost. Geochemical modeling found that Au was mainly present as AuHS(aq) and Au(HS)-2, and that the water-rock interactions decreased the sulfur fugacity which destroyed the stability of such aqueous complexes. Combined with the locally occurred native gold in quartz veins, it is concluded that the major gold precipitation mechanisms are sulfidation and fluid boiling. Based on previous geochronological and geochemical research further gold mineralization is proposed to be generated by deep sourced magmatic or metamorphic fluid migrated upward along the Woxi fault, and the iron-rich Madiyi Formation is the idea chemical trap for gold deposition. The decrease of sulfur contents caused by fluid-rock interactions and fluid boiling are the major mechanisms for gold mineralization.
