The Tiegelongnan deposit is a newly discovered super-large porphyry-epithermal Cu-（Au） deposit in the western part of the Bangong Co-Nujiang metallogenic belt, Tibet（China）. Field geology and geochronology indicat...The Tiegelongnan deposit is a newly discovered super-large porphyry-epithermal Cu-（Au） deposit in the western part of the Bangong Co-Nujiang metallogenic belt, Tibet（China）. Field geology and geochronology indicate that the porphyry mineralization was closely related to the Early Cretaceous intermediate-felsic intrusions（ca. 123–120 Ma）. Various epithermal ore and gangue mineral types were discovered in the middle-shallow part of the orebody, indicating the presence of epithermal mineralization at Tiegelongnan. Potassic, propylitic, phyllic and advanced argillic alteration zones were identified. 40Ar/39Ar dating of hydrothermal biotite（potassic zone）, sericite（phyllic zone）, and alunite（advanced argillic zone） in/around the ore-bearing granodiorite porphyry yielded 121.1±0.6 Ma（1σ）, 120.8±0.7 Ma（1σ） and 117.9±1.6 Ma（1σ）, respectively. Five hydrothermal mineralization stages were identified, of which the Stage IV pyrite was Rb-Sr dated to be 117.5±1.8 Ma（2σ）, representing the end of epithermal mineralization. Field geology and geochronology suggest that both the epithermal and porphyry mineralization belong to the same magmatic-hydrothermal system. The Tiegelongnan super-large Cu-（Au） deposit may have undergone a prolonged magmatichydrothermal evolution, with the major mineralization event occurring at ca.120–117Ma.展开更多
The newly discovered Zhunuo porphyry Cu-Mo-Au deposit is located in the western part of the Gangdese porphyry copper belt in southern Tibet, SW China. The granitoid plutons in the Zhunuo region are composed of quartz ...The newly discovered Zhunuo porphyry Cu-Mo-Au deposit is located in the western part of the Gangdese porphyry copper belt in southern Tibet, SW China. The granitoid plutons in the Zhunuo region are composed of quartz diorite porphyry, diorite porphyry, granodiorite porphyry, biotite monzogranite and quartz porphyry. The quartz diorite porphyry yielded zircon U-Pb ages of 51.9±0.7 Ma（Eocene） using LA-ICP-MS, whereas the diorite porphyry, granodiorite porphyry, biotite monzogranite and quartz porphyry yielded ages ranging from 16.2±0.2 to 14.0±0.2 Ma（Miocene）. CuMo-Au mineralization is mainly hosted in the Miocene granodiorite porphyry. Samples from all granitoid plutons have geochemical compositions consistent with high-K calc-alkaline series magmatism. The samples display highly fractionated light rare-earth element（REE） distributions and heavy REE distributions with weakly negative Eu anomalies on chondrite-normalized REE patterns. The trace element distributions exhibit positive anomalies for large-ion lithophile elements（Rb, K, U, Th and Pb） and negative anomalies for high-field-strength elements（Nb and Ti） relative to primitive mantlenormalized values. The Eocene quartz diorite porphyry yielded εNd（t） values ranging from-3.6 to-5.2,（-（87）Sr/-（86）Sr）i values in the range 0.7046–0.7063 and initial radiogenic Pb isotopic compositions with ranges of 18.599–18.657 -（206）Pb/-（204）Pb, 15.642–15.673 -（207）Pb/-（204）Pb and 38.956–39.199 -（208）Pb/-（204）Pb. In contrast, the Miocene granitoid plutons yielded ε（Nd）（t） values ranging from-6.1 to-7.3 and（87Sr/86Sr）i values in the range 0.7071–0.7078 with similar Pb isotopic compositions to the Eocene quart diorite. The Sr-Nd-Pb isotopic compositions of the rocks are consistent with formation from magma containing a component of remelted ancient crust. Zircon grains from the Eocene quartz diorite have ε（Hf）（t） values ranging from-5.2 to ＋0.9 and two-stage Hf model ages ranging from 1.07 to 1.46 Ga, while zircon grains from the Miocene granitoid plutons have ε（Hf）（t） values from-9.9 to ＋4.2 and two-stage Hf model ages ranging from 1.05–1.73 Ga, indicating that the ancient crustal component likely derives from Paleo- to Mesoproterozoic basement. This source is distinct from that of most porphyry Cu-Mo-Au deposits in the eastern part of the Gangdese porphyry copper belt, which likely originated from juvenile crust. We therefore consider melting of ancient crustal basement to have contributed significantly to the formation Miocene porphyry Cu-Mo-Au deposits in the western part of the Gangdese porphyry copper belt.展开更多
The paleohydrogeologic condition and the tectonic stress field during the mineralization epoch of the Au (Cu) ore fluid in the bordering orogenic belt of Simao-Nanping basin reveal that the complicated paleohydrodynam...The paleohydrogeologic condition and the tectonic stress field during the mineralization epoch of the Au (Cu) ore fluid in the bordering orogenic belt of Simao-Nanping basin reveal that the complicated paleohydrodynamic condition during the Devonian-Carboniferous period in the northern Ailao-shan was favorable for the pre-enrichment of the mineral elements, and that the migration and the distribution of the groundwater were controlled by the tectonic stress field and driven by temperature and hydraulic gradients during the Yanshan-Himalayan movement epoch. Therefore, the determination of the low-pressure zone of the maximum principal stress is effective for the location of the Au deposits (ore spots).展开更多
Petrographic and geochemical studies of syenite-looking Ayetoro and Sasaro plutons within Igarra Schist Belt were carried out in order to classify them and determine their tectonic setting and mineralization potential...Petrographic and geochemical studies of syenite-looking Ayetoro and Sasaro plutons within Igarra Schist Belt were carried out in order to classify them and determine their tectonic setting and mineralization potential. Petrographic study and geochemical classification revealed that while Ayetoro boss is microgranite constituting an aggregate of medium grained muscovite, quartz and biotite minerals, Sasaro stock is micromonzonite made up of medium grained albite, orthoclase, biotite, hornblende and pyroxene. Geotectonic setting showed the boss and stock are orogenic, probably derived from the same upper mantle magma as Igarra batholith that got contaminated by crustal materials responsible for their difference in lithology. Their mineralization potential showed that the massive Ayetoro microgranite with no appreciable trace-element contents cannot serve as host of any metallic deposit, and should be suitable for industrial applications. Whereas, the silicified, highly sheared Sasaro monzonite, with elevated level of some trace elements contents as Ag, Au and Cu, could harbor Ag-Au-Cu deposit.展开更多
The newly discovered Paodaoling porphyry Au deposit from the Guichi region, Lower Yangtze River Metallogenic Belt （LYRB）, contains 〉35 tons of Au at an average grade of -1.7 g/t. It is a porphyry ＇Au-only＇ deposi...The newly discovered Paodaoling porphyry Au deposit from the Guichi region, Lower Yangtze River Metallogenic Belt （LYRB）, contains 〉35 tons of Au at an average grade of -1.7 g/t. It is a porphyry ＇Au-only＇ deposit, as revealed by current exploration in the depths, mostly above -400 m, which is quite uncommon among coeval porphyry mineralization along the LYRB. Additionally, there are also Cu-Au bearing porphyries and barren alkaline granitoids in the Paodaoling district. Zircon LA-ICP-MS U-Pb dating of the Cu-Au-bearing porphyries yield an age of 141-140 Ma, falling within the main magmatic stage of the LYRB, whereas the barren granites give an age of 125-120 Ma, coeval with the regional A- type granites. The Cu-Au-bearing porphyries are LILE-, LREE-enriched and HFSE-depleted, typical of arc magmatic affinities. The barren granites are HFSE-enriched, with lower LREE/HREE ratios and pronounced negative Eu anomalies. The Cu-Au-bearing porphyries in the Paodaoling district have high oxygen fugacities and high water content. Pyrite sulfur isotopes of the Paodaoling gold deposit indicate a magmatic-sedimentary mixed source for the ore-forming fluids. Based on the alteration and poly-metal zonation of the deepest exploration drill hole from the Paodaoling Au deposit, we propose that Cu ore bodies could lie at depth beneath the current Au ore bodies. The magmatism and associated Cu-Au mineralization of the Paodaoling district are likely to have formed in a subduction setting, during slab rollback of the paleo-Pacific plate.展开更多
Duobaoshan is the largest porphyry-related Cu-Mo-Au orefield in northeastern(NE)Asia,and hosts a number of large-medium porphyry Cu(PCDs),epithermal Au and Fe-Cu skarn deposits.Formation ages of these deposits,from th...Duobaoshan is the largest porphyry-related Cu-Mo-Au orefield in northeastern(NE)Asia,and hosts a number of large-medium porphyry Cu(PCDs),epithermal Au and Fe-Cu skarn deposits.Formation ages of these deposits,from the oldest(Ordovician)to youngest(Jurassic),have spanned across over 300 Ma.No similar orefields of such size and geological complexity are found in NE Asia,which reflects its metallogenic uniqueness in forming and preserving porphyry-related deposits.In this study,we explore the actual number and timing of magmatic/mineralization phases,their respective magma genesis,fertility,and regional tectonic connection,together with the preservation of PCDs.We present new data on the magmatic/mineralization ages(LA-ICP-MS zircon U-Pb,pyrite and molybdenite Re-Os dating),whole-rock geochemistry,and zircon trace element compositions on four representative deposits in the Duobaoshan orefield,i.e.,Duobaoshan PCD,Tongshan PCD,Sankuanggou Fe-Cu skarn,and Zhengguang epithermal Au deposits,and compiled published ones from these and other mineral occurrences in the orefield.In terms of geochronology,we have newly summarized seven magmatic phases in the orefield:(1)Middle-Late Cambrian(506-491 Ma),(2)Early and Middle Ordovician(485-471 Ma and~462 Ma),(3)Late Ordovician(450-447 Ma),(4)Early Carboniferous and Late-Carboniferous to Early Permian(351-345 and 323-291 Ma),(5)Middle-Late Triassic(244-223 Ma),(6)Early-Middle and Late Jurassic(178-168 Ma and~150 Ma),and(7)Early Cretaceous(~112 Ma).Three of these seven major magmatic phases were coeval with ore formation,including(1)Early Ordovician(485-473 Ma)porphyry-type Cu-Mo-(Au),(2)Early-Middle Triassic(246-229 Ma)porphyry-related epithermal Au-(Cu-Mo),and(3)Early Jurassic(177-173 Ma)Fe-Cu skarn mineralization.Some deposits in the orefield,notably Tongshan and Zhengguang,were likely formed by more than one mineralization events.In terms of geochemistry,ore-causative granitoids in the orefield exhibit adakite-like or adakite-normal arc transitional signatures,but those forming the porphyry-/epithermal-type Cu-Mo-Au mineralization are largely confined to the former.The varying but high Sr/Y,Sm/Yb and La/Yb ratios suggest that the ore-forming magmas were mainly crustal sourced and formed at different depths(clinopyroxene-/amphibole-/garnet-stability fields).The adakite-like suites may have formed by partial melting of the thickened lower crust at 35-40 km(for the Early Ordovician arc)and>40 km(for the Middle-Late Triassic arc)depths.The Early Jurassic Fe-Cu skarn orecausative granitoids show an adakitic-normal arc transitional geochemical affinity.These granitoids were likely formed by partial melting of the juvenile lower crust(35-40 km depth),and subsequently modified by assimilation and fractional crystallization(AFC)processes.In light of the geological,geochronological and geochemical information,we proposed the following tectonometallogenic model for the Duobaoshan orefield.The Ordovician Duobaoshan may have been in a continental arc setting during the subduction of the Paleo-Asian Ocean,and formed the porphyry-related deposits at Duobaoshan,Tongshan and Zhengguang.Subduction may have ceased in the latest Ordovician,and the regional tectonics passed into long subsidence and extension till the latest Carboniferous.This extensional tectonic regime and the Silurian terrestrial-shallow marine sedimentation had likely buried and preserved the Ordovician Duobaoshan magmatic-hydrothermal system.The south-dipping Mongol-Okhotsk Ocean subduction from north of the orefield had generated the Middle-Late Triassic continental arc magmatism and the associated Tongshan PCD and Zhengguang epithermal Au mineralization(which superimposed on the Ordovician PCD system).The Middle Jurassic closure of Mongol-Okhotsk Ocean in the northwestern Amuria block(Erguna terrane),and the accompanying Siberia-Amuria collision,may have placed the Paleo-Pacific subduction system in NE China(including the orefield)under compression,and formed the granodiorite-tonalite and Fe-Cu skarn deposits at Sankuanggou and Xiaoduobaoshan.From the Middle Jurassic,the consecutive accretion of Paleo-Pacific arc terranes(e.g.,Sikhote-Alin and Nadanhada)onto the NE Asian continental margin may have gradually distant the Duobaoshan orefield from the subduction front,and consequently arc-type magmatism and the related mineralization faded.The minor Late Jurassic and Cretaceous unmineralized magmatism in the orefield may have triggered mainly by the far-field extension led by the post-collisional(Siberia-Amuria)gravitational collapse and/or Paleo-Pacific backarc-basin opening.展开更多
Four samples of plagioclase and biotite from the Shaxi porphyry in the lower part of the Yangtze metallogenic belt were analyzed for age determination with the ^40 Ar/^39Ar method. The results yield reproducible ages ...Four samples of plagioclase and biotite from the Shaxi porphyry in the lower part of the Yangtze metallogenic belt were analyzed for age determination with the ^40 Ar/^39Ar method. The results yield reproducible ages of 126 Ma to 135 Ma with a high level of confidence according to the agreement between isochron and plateau ages. The four Ar-Ar ages are relatively consistent within the analytical error. These ages are also consistent with, but more precise than, previous K-Ar and Rb-Sr ages and thus provide better constraints on the time of porphyry formation and associated Cu-Au mineralization along the middle to lower part of the Yangtze metallogenic belt. The ages of 126 to 135 Ma are interpreted to represent the intrusive time of the Shaxi porphyry, so that the Cu-Au mineralization should have occurred later due to the post-magmatic hydrothermal event.展开更多
Recently,continuous breakthroughs have been made about deep gold prospecting in the Jiaodong gold province area of China.Approximately 5000 t of cumulative gold resources have been explored in Jiaodong,which has thus ...Recently,continuous breakthroughs have been made about deep gold prospecting in the Jiaodong gold province area of China.Approximately 5000 t of cumulative gold resources have been explored in Jiaodong,which has thus become an internationally noteworthy gold ore cluster.The gold exploration depth has been increased to about 2000 m from the previous<1000 m.To further explore the mineralization potential of the Jiaodong area at a depth of about 3000 m,the Shandong Institute of Geological Sciences has drilled an exploratory drillhole named“Deep drillhole ZK01”to a depth of 3266 m.Hence,as reported herein,the mineralization characteristics of the Jiaojia metallogenic belt have been successfully documented.ZK01 is,to date,the deepest borehole with an gold intersect in China,and constitutes a significant advance in deep gold prospecting in China.The findings of this study further indicate that the depth interval of 2000 m to 4000 m below the ground surface in the Wuyi Village area incorporates 912 t of inferred gold resources,while the depth interval of 2000 m to 4000 m below the surface across the Jiaodong area possesses about 4000 t of inferred gold resources.The Jiaojia Fault Belt tends to gently dip downward,having dip angles of about 25°and about 20°at vertical depths of 2000 m and 2850 m,respectively.The deep part of the Jiaojia metallogenic belt differs from the shallow and moderately deep parts about fracturing,alteration,mineralization,and tectonic type.The deep zones can generally be categorized from inside outward as cataclastic granite,granitic cataclasite,weakly beresitized granitic cataclasite,beresitized cataclasite,and gouge.These zones exhibit a gradual transitional relation or occur alternately and repeatedly.The mineralization degree of the pyritized cataclastic granite-type ore in the deep part of the Jiaojia metallogenic belt is closely related to the degree of pyrite vein development;that is,the higher the pyrite content,the wider the veins and the higher the gold grade.Compared to the shallow gold ores,the deep-seated gold ores have higher fineness and contain joseite,tetradymite,and native bismuth,suggesting that the deep gold mineralization temperature is higher and that mantle-sourced material may have contributed to this mineralization.ZK01 has also revealed that the deep-seated ore bodies in the Jiaojia metallogenic belt are principally situated above the main fracture plane(gouge)and hosted within the Linglong Granite,contradicting previous findings indicating that the moderately shallow gold ore bodies are usually hosted in the contact zone between the Linglong Granite and Jiaodong Group or meta-gabbro.These new discoveries are particularly significant because they can help correct mineralization prospecting models,determine favorable positions for deep prospecting,and improve metallogenic prediction and resource potential evaluation.展开更多
基金jointly sponsored by the Public Science and Technology Research Funds Projects,Ministry of Land Resources of the People’s Republic of China(project No.201511017 and 201511022-02)the Basic Research Fund of the Chinese Academy of Geological Sciences(Grant No.YYWF201608)+3 种基金the National Natural Science Foundation of China(Grant No.41402178)Geological Survey Project of the China Geological Survey(project 1212011405040)Golden Dragon Mining Co.Ltd.(project XZJL-2013-JS03)China Scholarship Council
文摘The Tiegelongnan deposit is a newly discovered super-large porphyry-epithermal Cu-（Au） deposit in the western part of the Bangong Co-Nujiang metallogenic belt, Tibet（China）. Field geology and geochronology indicate that the porphyry mineralization was closely related to the Early Cretaceous intermediate-felsic intrusions（ca. 123–120 Ma）. Various epithermal ore and gangue mineral types were discovered in the middle-shallow part of the orebody, indicating the presence of epithermal mineralization at Tiegelongnan. Potassic, propylitic, phyllic and advanced argillic alteration zones were identified. 40Ar/39Ar dating of hydrothermal biotite（potassic zone）, sericite（phyllic zone）, and alunite（advanced argillic zone） in/around the ore-bearing granodiorite porphyry yielded 121.1±0.6 Ma（1σ）, 120.8±0.7 Ma（1σ） and 117.9±1.6 Ma（1σ）, respectively. Five hydrothermal mineralization stages were identified, of which the Stage IV pyrite was Rb-Sr dated to be 117.5±1.8 Ma（2σ）, representing the end of epithermal mineralization. Field geology and geochronology suggest that both the epithermal and porphyry mineralization belong to the same magmatic-hydrothermal system. The Tiegelongnan super-large Cu-（Au） deposit may have undergone a prolonged magmatichydrothermal evolution, with the major mineralization event occurring at ca.120–117Ma.
基金financially supported by National key research and development program of China:2016YFC0600308Chinese Geological survey project No.121201010000150014,1212011221073,12120114050701
文摘The newly discovered Zhunuo porphyry Cu-Mo-Au deposit is located in the western part of the Gangdese porphyry copper belt in southern Tibet, SW China. The granitoid plutons in the Zhunuo region are composed of quartz diorite porphyry, diorite porphyry, granodiorite porphyry, biotite monzogranite and quartz porphyry. The quartz diorite porphyry yielded zircon U-Pb ages of 51.9±0.7 Ma（Eocene） using LA-ICP-MS, whereas the diorite porphyry, granodiorite porphyry, biotite monzogranite and quartz porphyry yielded ages ranging from 16.2±0.2 to 14.0±0.2 Ma（Miocene）. CuMo-Au mineralization is mainly hosted in the Miocene granodiorite porphyry. Samples from all granitoid plutons have geochemical compositions consistent with high-K calc-alkaline series magmatism. The samples display highly fractionated light rare-earth element（REE） distributions and heavy REE distributions with weakly negative Eu anomalies on chondrite-normalized REE patterns. The trace element distributions exhibit positive anomalies for large-ion lithophile elements（Rb, K, U, Th and Pb） and negative anomalies for high-field-strength elements（Nb and Ti） relative to primitive mantlenormalized values. The Eocene quartz diorite porphyry yielded εNd（t） values ranging from-3.6 to-5.2,（-（87）Sr/-（86）Sr）i values in the range 0.7046–0.7063 and initial radiogenic Pb isotopic compositions with ranges of 18.599–18.657 -（206）Pb/-（204）Pb, 15.642–15.673 -（207）Pb/-（204）Pb and 38.956–39.199 -（208）Pb/-（204）Pb. In contrast, the Miocene granitoid plutons yielded ε（Nd）（t） values ranging from-6.1 to-7.3 and（87Sr/86Sr）i values in the range 0.7071–0.7078 with similar Pb isotopic compositions to the Eocene quart diorite. The Sr-Nd-Pb isotopic compositions of the rocks are consistent with formation from magma containing a component of remelted ancient crust. Zircon grains from the Eocene quartz diorite have ε（Hf）（t） values ranging from-5.2 to ＋0.9 and two-stage Hf model ages ranging from 1.07 to 1.46 Ga, while zircon grains from the Miocene granitoid plutons have ε（Hf）（t） values from-9.9 to ＋4.2 and two-stage Hf model ages ranging from 1.05–1.73 Ga, indicating that the ancient crustal component likely derives from Paleo- to Mesoproterozoic basement. This source is distinct from that of most porphyry Cu-Mo-Au deposits in the eastern part of the Gangdese porphyry copper belt, which likely originated from juvenile crust. We therefore consider melting of ancient crustal basement to have contributed significantly to the formation Miocene porphyry Cu-Mo-Au deposits in the western part of the Gangdese porphyry copper belt.
基金This paper is supported by NKBRSF Project (No. G1999043205) the Returned Studenes Fund of CME.
文摘The paleohydrogeologic condition and the tectonic stress field during the mineralization epoch of the Au (Cu) ore fluid in the bordering orogenic belt of Simao-Nanping basin reveal that the complicated paleohydrodynamic condition during the Devonian-Carboniferous period in the northern Ailao-shan was favorable for the pre-enrichment of the mineral elements, and that the migration and the distribution of the groundwater were controlled by the tectonic stress field and driven by temperature and hydraulic gradients during the Yanshan-Himalayan movement epoch. Therefore, the determination of the low-pressure zone of the maximum principal stress is effective for the location of the Au deposits (ore spots).
文摘Petrographic and geochemical studies of syenite-looking Ayetoro and Sasaro plutons within Igarra Schist Belt were carried out in order to classify them and determine their tectonic setting and mineralization potential. Petrographic study and geochemical classification revealed that while Ayetoro boss is microgranite constituting an aggregate of medium grained muscovite, quartz and biotite minerals, Sasaro stock is micromonzonite made up of medium grained albite, orthoclase, biotite, hornblende and pyroxene. Geotectonic setting showed the boss and stock are orogenic, probably derived from the same upper mantle magma as Igarra batholith that got contaminated by crustal materials responsible for their difference in lithology. Their mineralization potential showed that the massive Ayetoro microgranite with no appreciable trace-element contents cannot serve as host of any metallic deposit, and should be suitable for industrial applications. Whereas, the silicified, highly sheared Sasaro monzonite, with elevated level of some trace elements contents as Ag, Au and Cu, could harbor Ag-Au-Cu deposit.
基金supported by the National Key R&D Program of China(No.2016YFC0600404)the National Natural Science Foundation of China(Grant Nos.41673040 and 41611540339)the Project of National Land Resource Science and Technology of Anhui Province(2014-K-4)
文摘The newly discovered Paodaoling porphyry Au deposit from the Guichi region, Lower Yangtze River Metallogenic Belt （LYRB）, contains 〉35 tons of Au at an average grade of -1.7 g/t. It is a porphyry ＇Au-only＇ deposit, as revealed by current exploration in the depths, mostly above -400 m, which is quite uncommon among coeval porphyry mineralization along the LYRB. Additionally, there are also Cu-Au bearing porphyries and barren alkaline granitoids in the Paodaoling district. Zircon LA-ICP-MS U-Pb dating of the Cu-Au-bearing porphyries yield an age of 141-140 Ma, falling within the main magmatic stage of the LYRB, whereas the barren granites give an age of 125-120 Ma, coeval with the regional A- type granites. The Cu-Au-bearing porphyries are LILE-, LREE-enriched and HFSE-depleted, typical of arc magmatic affinities. The barren granites are HFSE-enriched, with lower LREE/HREE ratios and pronounced negative Eu anomalies. The Cu-Au-bearing porphyries in the Paodaoling district have high oxygen fugacities and high water content. Pyrite sulfur isotopes of the Paodaoling gold deposit indicate a magmatic-sedimentary mixed source for the ore-forming fluids. Based on the alteration and poly-metal zonation of the deepest exploration drill hole from the Paodaoling Au deposit, we propose that Cu ore bodies could lie at depth beneath the current Au ore bodies. The magmatism and associated Cu-Au mineralization of the Paodaoling district are likely to have formed in a subduction setting, during slab rollback of the paleo-Pacific plate.
基金funded by the China Geological Survey,the Chinese Ministry of Science and Technology(2017YFC0601304)the Cu-Mo-Au-Ag Metallogenic Regularity in Duobaoshan-Sankuanggou Belt Project(DT-2017-SJC-12)。
文摘Duobaoshan is the largest porphyry-related Cu-Mo-Au orefield in northeastern(NE)Asia,and hosts a number of large-medium porphyry Cu(PCDs),epithermal Au and Fe-Cu skarn deposits.Formation ages of these deposits,from the oldest(Ordovician)to youngest(Jurassic),have spanned across over 300 Ma.No similar orefields of such size and geological complexity are found in NE Asia,which reflects its metallogenic uniqueness in forming and preserving porphyry-related deposits.In this study,we explore the actual number and timing of magmatic/mineralization phases,their respective magma genesis,fertility,and regional tectonic connection,together with the preservation of PCDs.We present new data on the magmatic/mineralization ages(LA-ICP-MS zircon U-Pb,pyrite and molybdenite Re-Os dating),whole-rock geochemistry,and zircon trace element compositions on four representative deposits in the Duobaoshan orefield,i.e.,Duobaoshan PCD,Tongshan PCD,Sankuanggou Fe-Cu skarn,and Zhengguang epithermal Au deposits,and compiled published ones from these and other mineral occurrences in the orefield.In terms of geochronology,we have newly summarized seven magmatic phases in the orefield:(1)Middle-Late Cambrian(506-491 Ma),(2)Early and Middle Ordovician(485-471 Ma and~462 Ma),(3)Late Ordovician(450-447 Ma),(4)Early Carboniferous and Late-Carboniferous to Early Permian(351-345 and 323-291 Ma),(5)Middle-Late Triassic(244-223 Ma),(6)Early-Middle and Late Jurassic(178-168 Ma and~150 Ma),and(7)Early Cretaceous(~112 Ma).Three of these seven major magmatic phases were coeval with ore formation,including(1)Early Ordovician(485-473 Ma)porphyry-type Cu-Mo-(Au),(2)Early-Middle Triassic(246-229 Ma)porphyry-related epithermal Au-(Cu-Mo),and(3)Early Jurassic(177-173 Ma)Fe-Cu skarn mineralization.Some deposits in the orefield,notably Tongshan and Zhengguang,were likely formed by more than one mineralization events.In terms of geochemistry,ore-causative granitoids in the orefield exhibit adakite-like or adakite-normal arc transitional signatures,but those forming the porphyry-/epithermal-type Cu-Mo-Au mineralization are largely confined to the former.The varying but high Sr/Y,Sm/Yb and La/Yb ratios suggest that the ore-forming magmas were mainly crustal sourced and formed at different depths(clinopyroxene-/amphibole-/garnet-stability fields).The adakite-like suites may have formed by partial melting of the thickened lower crust at 35-40 km(for the Early Ordovician arc)and>40 km(for the Middle-Late Triassic arc)depths.The Early Jurassic Fe-Cu skarn orecausative granitoids show an adakitic-normal arc transitional geochemical affinity.These granitoids were likely formed by partial melting of the juvenile lower crust(35-40 km depth),and subsequently modified by assimilation and fractional crystallization(AFC)processes.In light of the geological,geochronological and geochemical information,we proposed the following tectonometallogenic model for the Duobaoshan orefield.The Ordovician Duobaoshan may have been in a continental arc setting during the subduction of the Paleo-Asian Ocean,and formed the porphyry-related deposits at Duobaoshan,Tongshan and Zhengguang.Subduction may have ceased in the latest Ordovician,and the regional tectonics passed into long subsidence and extension till the latest Carboniferous.This extensional tectonic regime and the Silurian terrestrial-shallow marine sedimentation had likely buried and preserved the Ordovician Duobaoshan magmatic-hydrothermal system.The south-dipping Mongol-Okhotsk Ocean subduction from north of the orefield had generated the Middle-Late Triassic continental arc magmatism and the associated Tongshan PCD and Zhengguang epithermal Au mineralization(which superimposed on the Ordovician PCD system).The Middle Jurassic closure of Mongol-Okhotsk Ocean in the northwestern Amuria block(Erguna terrane),and the accompanying Siberia-Amuria collision,may have placed the Paleo-Pacific subduction system in NE China(including the orefield)under compression,and formed the granodiorite-tonalite and Fe-Cu skarn deposits at Sankuanggou and Xiaoduobaoshan.From the Middle Jurassic,the consecutive accretion of Paleo-Pacific arc terranes(e.g.,Sikhote-Alin and Nadanhada)onto the NE Asian continental margin may have gradually distant the Duobaoshan orefield from the subduction front,and consequently arc-type magmatism and the related mineralization faded.The minor Late Jurassic and Cretaceous unmineralized magmatism in the orefield may have triggered mainly by the far-field extension led by the post-collisional(Siberia-Amuria)gravitational collapse and/or Paleo-Pacific backarc-basin opening.
基金This study is supported by funds from the Ministry of Science and Technology of China （2006CB403500） ； National Natural Science Foundation of China （40473021）.
文摘Four samples of plagioclase and biotite from the Shaxi porphyry in the lower part of the Yangtze metallogenic belt were analyzed for age determination with the ^40 Ar/^39Ar method. The results yield reproducible ages of 126 Ma to 135 Ma with a high level of confidence according to the agreement between isochron and plateau ages. The four Ar-Ar ages are relatively consistent within the analytical error. These ages are also consistent with, but more precise than, previous K-Ar and Rb-Sr ages and thus provide better constraints on the time of porphyry formation and associated Cu-Au mineralization along the middle to lower part of the Yangtze metallogenic belt. The ages of 126 to 135 Ma are interpreted to represent the intrusive time of the Shaxi porphyry, so that the Cu-Au mineralization should have occurred later due to the post-magmatic hydrothermal event.
基金by the National Natural Science Foundation of China(41772076,41672084,41372086,41503038)the National Key Research and Development Program of China(2016YFC0600105-04,2016YFC0600606)+1 种基金the Key Research and Development Program of Shandong Province(2017CXGC1601,2017CXGC1602,2017CXGC1603),the Special Fund for“Taishan Scholars”Project of Shandong Province.
文摘Recently,continuous breakthroughs have been made about deep gold prospecting in the Jiaodong gold province area of China.Approximately 5000 t of cumulative gold resources have been explored in Jiaodong,which has thus become an internationally noteworthy gold ore cluster.The gold exploration depth has been increased to about 2000 m from the previous<1000 m.To further explore the mineralization potential of the Jiaodong area at a depth of about 3000 m,the Shandong Institute of Geological Sciences has drilled an exploratory drillhole named“Deep drillhole ZK01”to a depth of 3266 m.Hence,as reported herein,the mineralization characteristics of the Jiaojia metallogenic belt have been successfully documented.ZK01 is,to date,the deepest borehole with an gold intersect in China,and constitutes a significant advance in deep gold prospecting in China.The findings of this study further indicate that the depth interval of 2000 m to 4000 m below the ground surface in the Wuyi Village area incorporates 912 t of inferred gold resources,while the depth interval of 2000 m to 4000 m below the surface across the Jiaodong area possesses about 4000 t of inferred gold resources.The Jiaojia Fault Belt tends to gently dip downward,having dip angles of about 25°and about 20°at vertical depths of 2000 m and 2850 m,respectively.The deep part of the Jiaojia metallogenic belt differs from the shallow and moderately deep parts about fracturing,alteration,mineralization,and tectonic type.The deep zones can generally be categorized from inside outward as cataclastic granite,granitic cataclasite,weakly beresitized granitic cataclasite,beresitized cataclasite,and gouge.These zones exhibit a gradual transitional relation or occur alternately and repeatedly.The mineralization degree of the pyritized cataclastic granite-type ore in the deep part of the Jiaojia metallogenic belt is closely related to the degree of pyrite vein development;that is,the higher the pyrite content,the wider the veins and the higher the gold grade.Compared to the shallow gold ores,the deep-seated gold ores have higher fineness and contain joseite,tetradymite,and native bismuth,suggesting that the deep gold mineralization temperature is higher and that mantle-sourced material may have contributed to this mineralization.ZK01 has also revealed that the deep-seated ore bodies in the Jiaojia metallogenic belt are principally situated above the main fracture plane(gouge)and hosted within the Linglong Granite,contradicting previous findings indicating that the moderately shallow gold ore bodies are usually hosted in the contact zone between the Linglong Granite and Jiaodong Group or meta-gabbro.These new discoveries are particularly significant because they can help correct mineralization prospecting models,determine favorable positions for deep prospecting,and improve metallogenic prediction and resource potential evaluation.
