The Nanling Range in South China is well known for its rich granite-related W–Sn deposits.To elucidate the controls of different granite-related W–Sn metallogenesis in the region,we chose five representative orerela...The Nanling Range in South China is well known for its rich granite-related W–Sn deposits.To elucidate the controls of different granite-related W–Sn metallogenesis in the region,we chose five representative orerelated granites(Yanbei,Mikengshan,Tieshanlong,Qianlishan,and Yaogangxian intrusions)in the Hunan–Jiangxi region,and studied their magmatic zircon ages and trace element geochemistry.Our new zircon data showed the differences in ages,temperatures and oxygen fugacity of the ore-forming magmas.Zircon U–Pb ages of the Yanbei and Mikengshan intrusions are characterized by 142.4±2.4 and 143.0±2.3 Ma,respectively,whereas the Tieshanlong and Qianlishan intrusions are 159.5±2.3and 153.2±3.3 Ma,respectively.The Sn-related intrusions were younger than the W-related intrusions.The Tiin-zircon thermometry showed that there was no systematic difference between the Sn-related Yanbei(680–744℃)and Mikengshan(697–763℃)intrusions and the W-related Tieshanlong(730–800℃),Qianlishan(690–755℃)and Yaogangxian(686–751℃)intrusions.However,the zircon Ce^4+/Ce^3+ratios of the Yanbei(averaged at 18.3)and Mikengshan(averaged at 18.8)intrusions are lower than those of the Tieshanlong(averaged at 36.9),Qianlishan(averaged at 38.4)and Yaogangxian(averaged at 37)intrusions,indicating that the Sn-related granitic magmas might have lower oxygen fugacities than those of the W-related.This can be explained by that,in more reduced magmas,Sn is more soluble than W and thus is more enriched in the residual melt to form Sn mineralization.The difference in source materials between the Sn-related and the W-related granites seems to have contributed to the different redox conditions of the melts.展开更多
Previous studies have obtained some petrogenetic and metallogenic chronological data with SHRIMP （sensitive high-resolution ion microprobe） zircon U-Pb, zircon LA-ICPMS （laser-ablation-inductively coupled plasma ma...Previous studies have obtained some petrogenetic and metallogenic chronological data with SHRIMP （sensitive high-resolution ion microprobe） zircon U-Pb, zircon LA-ICPMS （laser-ablation-inductively coupled plasma mass spectroscopy） U-Pb, molybdenite Re-Os isochron and muscovite Ar-Ar methods in southern Jiangxi Province and its adjacent areas. Based on these, the purpose of this paper is to study the petrogenetic and metallogenic ages and their time gap for different genetic types of W-Sn deposits, and thus to research their numerous episodes, zonal arrangement and their geodynamic background. The result shows that the large-scale W-Sn mineralization in southern Jiangxi Province occurred in the middle to late Jurassic （170-150 Ma）, the skarn W-Sn-polymetallic deposits formed much earlier （170-161 Ma）, and all of the wolframite-quartz vein type, greisen type, altered granite type and fractured zone type tungsten deposits formed in the late Jurassic （160-150 Ma）. In one ore field or ore district, greisen type tungsten deposits formed earlier than quartz vein type ones hosted in the endoor exo-contact zone; and quartz vein type hosted in the endocontact zone formed earlier than that of exocontact zone. There is no significant time difference between tungstentin mineralization and its intimately associated parent granite emplacement （1-6 Ma）. They all formed in the same rock-forming and ore-forming system and under the same geodynamic setting. Regionally, rock-forming and ore-forming processes of the W-Sn deposits in the Nanling region （include southern Jiangxi Province, southern Hunan Province, northern Guangdong Province and eastern Guangxi Zhuang Autonomous Region） exhibit numerous episodes. The mineralization in the Nanling region mainly occurred at （240-210） Ma, （170-150） Ma and （130-90） Ma. The tungsten-tin deposits in this region are centered by the largest scale in southern Jiangxi Province and southern Hunan Province, and become small in the east, west, south and north directions. This displays a zonal arrangement and temporal and spatial distribution regularity. Integrated with the latest research results, it is concluded that the W-Sn mineralization in southern Jiangxi Province and its adjacent areas corresponds to the second large-scale mineralization in South China. The Indosinian W-Sn mineralization formed under the extensional tectonic regime between collisional compressional stages, while the Yanshanian large-scale petrogenetic and metallogenic processes occurred in the Jurassic intraplate extensional geodynamic setting of lithosphere extension.展开更多
The stability of underground excavations has become an important issue in order to extend underground mining operations and extract deeper deposits. The increasing demand for Tin-Tungsten (Sn-W) for industry and its m...The stability of underground excavations has become an important issue in order to extend underground mining operations and extract deeper deposits. The increasing demand for Tin-Tungsten (Sn-W) for industry and its market price has created a motivation for mining companies to extract deep-seated Sn-W ore deposits in Myanmar. Thus, this paper aims to investigate the stability of underground openings, especially, the stope with considering the mining methods. To meet the objective, FLAC<sup>3D</sup> 5.0 simulation was used for the assessment of stope under different stress ratios, 0.5, 1.0, and 1.5 for two types of underground mines;Open stoping and Cut and Fill stoping. The results show that the risk of instability of stope is high under the stress ratio of <em>K</em> = 0.5 than that of <em>K</em> = 1.0 and <em>K</em> = 1.5 in both mining methods. However, the stability of the stope in open stope method is lower than that of cut-and-fill method obviously. This result shows that the appropriate mining method has to be selected for extraction of Sn-W deposit carefully in terms of the balance of safety and cost.展开更多
The Hermyingyi W-Sn deposit, situated in southern Myanmar, SE Asia, is a typical quartz-vein type W-Sn deposit. The ore-bearing quartz veins are mainly hosted by the Hermyingyi monzogranite which intruded into the Car...The Hermyingyi W-Sn deposit, situated in southern Myanmar, SE Asia, is a typical quartz-vein type W-Sn deposit. The ore-bearing quartz veins are mainly hosted by the Hermyingyi monzogranite which intruded into the Carboniferous metasedimentary rocks of Mergui Series. According to mineral assemblages and crosscutting relationships, four ore-forming stages are recognized:(1) silicate-oxide stage;(2) quartz-sulfide stage;(3) barren quartz vein stage;(4) supergene stage. Five molybdenite samples from the deposit yield Re-Os model ages ranging from 67.8±1.6 to 69.2±1.6 Ma(weighted mean age of 68.7±1.2 Ma), and a well-defined isochron age of 68.4±2.5 Ma(MSWD=0.18, 2σ). This Re-Os age is consistent with the previously published zircon U-Pb age of the Hermyingyi monzogranite(70.0±0.4 Ma)(MSWD=0.9, 2σ) within errors, which indicates a genetic link between the monzogranitic magmatism and W-Sn mineralization. The new high-precision geochronological data reveal that the granitic magmatism and associated W-Sn mineralization in southern Myanmar took place during the Late Cretaceous(70–68 Ma). The extremely low Re contents(22.9 ppb to 299 ppb) in molybdenite, coupled with sulfide δ^(34)S values in the range of +1.9‰ to +5.6‰ suggest that ore-forming metals were predominately sourced from the crustal-derived granitic magma.展开更多
Concentration of elements or element groups in a geological body is the result of multiple stages of rockforming and ore-forming geological processes.An ore-forming element group can be identified by PCA(principal com...Concentration of elements or element groups in a geological body is the result of multiple stages of rockforming and ore-forming geological processes.An ore-forming element group can be identified by PCA(principal component analysis)and be separated into two components using BEMD(bi-dimensional empirical mode decomposition):(1)a high background component which represents the ore-forming background developed in rocks through various geological processes favorable for mineralization(i.e.magmatism,sedimentation and/or metamorphism);(2)the anomaly component which reflects the oreforming anomaly that is overprinted on the high background component developed during mineralization.Anomaly components are used to identify ore-finding targets more effectively than ore-forming element groups.Three steps of data analytical procedures are described in this paper;firstly,the application of PCA to establish the ore-forming element group;secondly,using BEMD on the o re-forming element group to identify the anomaly components created by different types of mineralization processes;and finally,identifying ore-finding targets based on the anomaly components.This method is applied to the Tengchong tin-polymetallic belt to delineate ore-finding targets,where four targets for Sn(W)and three targets for Pb-Zn-Ag-Fe polymetallic mineralization are identified and defined as new areas for further prospecting.It is shown that BEMD combined with PCA can be applied not only in extracting the anomaly component for delineating the ore-finding target,but also in extracting the residual component for identifying its high background zone favorable for mineralization from its oreforming element group.展开更多
基金supported by the National Basic Research Program of China (973 Program) (Grants No. 2014CB440906)Innovation Team Program of Chinese Academy of Sciences (Overseas Famous Scholars Program)‘‘Light of West China’’ Program of Chinese Academy of Sciences
文摘The Nanling Range in South China is well known for its rich granite-related W–Sn deposits.To elucidate the controls of different granite-related W–Sn metallogenesis in the region,we chose five representative orerelated granites(Yanbei,Mikengshan,Tieshanlong,Qianlishan,and Yaogangxian intrusions)in the Hunan–Jiangxi region,and studied their magmatic zircon ages and trace element geochemistry.Our new zircon data showed the differences in ages,temperatures and oxygen fugacity of the ore-forming magmas.Zircon U–Pb ages of the Yanbei and Mikengshan intrusions are characterized by 142.4±2.4 and 143.0±2.3 Ma,respectively,whereas the Tieshanlong and Qianlishan intrusions are 159.5±2.3and 153.2±3.3 Ma,respectively.The Sn-related intrusions were younger than the W-related intrusions.The Tiin-zircon thermometry showed that there was no systematic difference between the Sn-related Yanbei(680–744℃)and Mikengshan(697–763℃)intrusions and the W-related Tieshanlong(730–800℃),Qianlishan(690–755℃)and Yaogangxian(686–751℃)intrusions.However,the zircon Ce^4+/Ce^3+ratios of the Yanbei(averaged at 18.3)and Mikengshan(averaged at 18.8)intrusions are lower than those of the Tieshanlong(averaged at 36.9),Qianlishan(averaged at 38.4)and Yaogangxian(averaged at 37)intrusions,indicating that the Sn-related granitic magmas might have lower oxygen fugacities than those of the W-related.This can be explained by that,in more reduced magmas,Sn is more soluble than W and thus is more enriched in the residual melt to form Sn mineralization.The difference in source materials between the Sn-related and the W-related granites seems to have contributed to the different redox conditions of the melts.
基金financially supported by the National Key Basic Research Program (Grant2012CB416704) from the Ministry of Science and Technology, Chinagrant No. 40772063 from the National Natural Science Foundation of China+1 种基金the Program of Excellent Young Scientists from the Ministry of Land and Resources (200809)Geological Survey Program Grant 1212010561603-2 from the China Geological Survey
文摘Previous studies have obtained some petrogenetic and metallogenic chronological data with SHRIMP （sensitive high-resolution ion microprobe） zircon U-Pb, zircon LA-ICPMS （laser-ablation-inductively coupled plasma mass spectroscopy） U-Pb, molybdenite Re-Os isochron and muscovite Ar-Ar methods in southern Jiangxi Province and its adjacent areas. Based on these, the purpose of this paper is to study the petrogenetic and metallogenic ages and their time gap for different genetic types of W-Sn deposits, and thus to research their numerous episodes, zonal arrangement and their geodynamic background. The result shows that the large-scale W-Sn mineralization in southern Jiangxi Province occurred in the middle to late Jurassic （170-150 Ma）, the skarn W-Sn-polymetallic deposits formed much earlier （170-161 Ma）, and all of the wolframite-quartz vein type, greisen type, altered granite type and fractured zone type tungsten deposits formed in the late Jurassic （160-150 Ma）. In one ore field or ore district, greisen type tungsten deposits formed earlier than quartz vein type ones hosted in the endoor exo-contact zone; and quartz vein type hosted in the endocontact zone formed earlier than that of exocontact zone. There is no significant time difference between tungstentin mineralization and its intimately associated parent granite emplacement （1-6 Ma）. They all formed in the same rock-forming and ore-forming system and under the same geodynamic setting. Regionally, rock-forming and ore-forming processes of the W-Sn deposits in the Nanling region （include southern Jiangxi Province, southern Hunan Province, northern Guangdong Province and eastern Guangxi Zhuang Autonomous Region） exhibit numerous episodes. The mineralization in the Nanling region mainly occurred at （240-210） Ma, （170-150） Ma and （130-90） Ma. The tungsten-tin deposits in this region are centered by the largest scale in southern Jiangxi Province and southern Hunan Province, and become small in the east, west, south and north directions. This displays a zonal arrangement and temporal and spatial distribution regularity. Integrated with the latest research results, it is concluded that the W-Sn mineralization in southern Jiangxi Province and its adjacent areas corresponds to the second large-scale mineralization in South China. The Indosinian W-Sn mineralization formed under the extensional tectonic regime between collisional compressional stages, while the Yanshanian large-scale petrogenetic and metallogenic processes occurred in the Jurassic intraplate extensional geodynamic setting of lithosphere extension.
文摘The stability of underground excavations has become an important issue in order to extend underground mining operations and extract deeper deposits. The increasing demand for Tin-Tungsten (Sn-W) for industry and its market price has created a motivation for mining companies to extract deep-seated Sn-W ore deposits in Myanmar. Thus, this paper aims to investigate the stability of underground openings, especially, the stope with considering the mining methods. To meet the objective, FLAC<sup>3D</sup> 5.0 simulation was used for the assessment of stope under different stress ratios, 0.5, 1.0, and 1.5 for two types of underground mines;Open stoping and Cut and Fill stoping. The results show that the risk of instability of stope is high under the stress ratio of <em>K</em> = 0.5 than that of <em>K</em> = 1.0 and <em>K</em> = 1.5 in both mining methods. However, the stability of the stope in open stope method is lower than that of cut-and-fill method obviously. This result shows that the appropriate mining method has to be selected for extraction of Sn-W deposit carefully in terms of the balance of safety and cost.
基金financially supported by the National Key R&D Program of China (No. 2017YFC0602405)the National Natural Science Foundation of China (Nos. 41503043, 91755208)the MOST Special Fund from the State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences (No. MSFGPMR03-2)
文摘The Hermyingyi W-Sn deposit, situated in southern Myanmar, SE Asia, is a typical quartz-vein type W-Sn deposit. The ore-bearing quartz veins are mainly hosted by the Hermyingyi monzogranite which intruded into the Carboniferous metasedimentary rocks of Mergui Series. According to mineral assemblages and crosscutting relationships, four ore-forming stages are recognized:(1) silicate-oxide stage;(2) quartz-sulfide stage;(3) barren quartz vein stage;(4) supergene stage. Five molybdenite samples from the deposit yield Re-Os model ages ranging from 67.8±1.6 to 69.2±1.6 Ma(weighted mean age of 68.7±1.2 Ma), and a well-defined isochron age of 68.4±2.5 Ma(MSWD=0.18, 2σ). This Re-Os age is consistent with the previously published zircon U-Pb age of the Hermyingyi monzogranite(70.0±0.4 Ma)(MSWD=0.9, 2σ) within errors, which indicates a genetic link between the monzogranitic magmatism and W-Sn mineralization. The new high-precision geochronological data reveal that the granitic magmatism and associated W-Sn mineralization in southern Myanmar took place during the Late Cretaceous(70–68 Ma). The extremely low Re contents(22.9 ppb to 299 ppb) in molybdenite, coupled with sulfide δ^(34)S values in the range of +1.9‰ to +5.6‰ suggest that ore-forming metals were predominately sourced from the crustal-derived granitic magma.
基金funded by the Na-tional Natural Science Foundation of China(Grant Nos.41672329,41272365)the National Key Research and Development Project of China(Grant No.2016YFC0600509)the Project of China Geological Survey(Grant No.1212011120341)
文摘Concentration of elements or element groups in a geological body is the result of multiple stages of rockforming and ore-forming geological processes.An ore-forming element group can be identified by PCA(principal component analysis)and be separated into two components using BEMD(bi-dimensional empirical mode decomposition):(1)a high background component which represents the ore-forming background developed in rocks through various geological processes favorable for mineralization(i.e.magmatism,sedimentation and/or metamorphism);(2)the anomaly component which reflects the oreforming anomaly that is overprinted on the high background component developed during mineralization.Anomaly components are used to identify ore-finding targets more effectively than ore-forming element groups.Three steps of data analytical procedures are described in this paper;firstly,the application of PCA to establish the ore-forming element group;secondly,using BEMD on the o re-forming element group to identify the anomaly components created by different types of mineralization processes;and finally,identifying ore-finding targets based on the anomaly components.This method is applied to the Tengchong tin-polymetallic belt to delineate ore-finding targets,where four targets for Sn(W)and three targets for Pb-Zn-Ag-Fe polymetallic mineralization are identified and defined as new areas for further prospecting.It is shown that BEMD combined with PCA can be applied not only in extracting the anomaly component for delineating the ore-finding target,but also in extracting the residual component for identifying its high background zone favorable for mineralization from its oreforming element group.
