The Mamupu skarn-type Cu-Au polymetallic deposit represents the first discovery of a medium deposit in the southern Yulong porphyry copper belt(YPCB),eastern Tibet.The Cu-Au mineralization mainly occurs as chalcopyrit...The Mamupu skarn-type Cu-Au polymetallic deposit represents the first discovery of a medium deposit in the southern Yulong porphyry copper belt(YPCB),eastern Tibet.The Cu-Au mineralization mainly occurs as chalcopyrite in breccia,within the plate-like carbonate interlayer,being closely related to chloritization(e.g.,chlorite,magnetite and epidote)and skarnization(e.g.,diopside,tremolite and garnet).The ore-related quartz syenite porphyry(QSP)and granodiorite porphyry(GP)were emplaced at 40.1±0.2 Ma and 39.9±0.3 Ma,respectively.The QSP of Mamupu is an alkaline-rich intrusion,relatively enriched in LREE,LILE,depleted in HFSE,with no significant negative Eu and Ce anomalies,slightly high(^(87)Sr/^(86)Sr)i,lowε_(Nd)(t),uniform(^(206)Pb/^(204)Pb)i andε_(Hf)(t)values,which indicates that the porphyry magma may be caused by both the mixing of metasomatized EM II enriched mantle and thickened juvenile lower crust.The QSP in the Mamupu deposit shares a similar genesis of petrology to other ore-related porphyries within the YPCB.High oxygen fugacity and water content of the magmas are essential for the formation of porphyry and skarn Cu deposits.The QSP has similar high magmatic oxidation states and water content to the Yulong deposit,which indicates that the Mamupu has a high prospecting potential.Differences in the geological characteristics and scale of mineralization between the Mamupu and other YPCB deposits may be due to the different emplacement depths of ore-related intrusions,as well as differences in the surrounding rocks.展开更多
The Oyu Tolgoi cluster of seven porphyry Cu-Au-Mo deposits in southern Mongolia,define a narrow,linear,12 km long,almost continuously mineralised trend,which contains in excess of 42 Mt of Cu and1850 t of Au,and is am...The Oyu Tolgoi cluster of seven porphyry Cu-Au-Mo deposits in southern Mongolia,define a narrow,linear,12 km long,almost continuously mineralised trend,which contains in excess of 42 Mt of Cu and1850 t of Au,and is among the largest high grade porphyry Cu-Au deposits in the world.These deposits lie within the Gurvansayhan island-arc terrane,a fault bounded segment of the broader Silurian to Carboniferous Kazakh-Mongol arc,located towards the southern margin of the Central Asian Orogenic Belt,a collage of magmatic arcs that were periodically active from the late Neoproterozoic to PermoTriassic,extending from the Urals Mountains to the Pacific Ocean.Mineralisation at Oyu Tolgoi is associated with multiple,overlapping,intrusions of late Devonian（～372 to 370 Ma） quartzmonzodiorite intruding Devonian（or older） juvenile,probably intra-oceanic arc-related,basaltic lavas and lesser volcaniclastic rocks,unconformably overlain by late Devonian（～370 Ma） basaltic to dacitic pyroclastic and volcano sedimentary rocks.These quartz-monzodiorite intrusions range from earlymineral porphyritic dykes,to larger,linear,syn-,late- and post-mineral dykes and stocks.Ore was deposited within syn-mineral quartz-monzodiorites,but is dominantly hosted by augite basalts and to a lesser degree by overlying dacitic pyroclastic rocks.Following ore deposition,an allochthonous plate of older Devonian（or pre-Devonian） rocks was overthrust and a post-ore biotite granodiorite intruded at～365 Ma.Mineralisation is characterised by varying,telescoped stages of intrusion and alteration.Early A-type quartz veined dykes were followed by Cu-Au mineralisation associated with potassic alteration,mainly K-feldspar in quartz-monzodiorite and biotite-magnetite in basaltic hosts.Downward reflux of cooled,late-magmatic hydrothermal fluid resulted in intense quartz-sericite retrograde alteration in the upper parts of the main syn-mineral intrusions,and an equivalent chlorite-muscovite/illite-hematite assemblage in basaltic host rocks.Uplift,facilitated by syn-mineral longitudinal faulting,brought sections of the porphyry deposit to shallower depths,to be overprinted and upgraded by late stage,shallower,advanced argillic alteration and high sulphidation mineralisation.Key controls on the location,size and grade of the deposit cluster include（i） a long-lived,narrow faulted corridor;（ii） multiple pulses of overlapping intrusion within the same structure;and（iii） enclosing reactive,mafic dominated wall rocks,focussing ore.展开更多
The Yulong supper\|large copper deposit is situated within the well\|known S\|N striking Yulong copper\|molybdenum ore belt. The ore\|bearing biotite\|monogranitic porphyry was emplaced within clastic rocks (mainly sh...The Yulong supper\|large copper deposit is situated within the well\|known S\|N striking Yulong copper\|molybdenum ore belt. The ore\|bearing biotite\|monogranitic porphyry was emplaced within clastic rocks (mainly shales and siltstones) of the Jiapila Formation (T 3 j ) and carbonate rocks of the Bolila Formation (T 3 b ) of the Upper Triassic. Five mineralization patterns have been recognized in the deposit, i.e., ①veinlet\|disseminated Cu\|Mo ore in the porphyry; ②skarn\|type Cu ore at the contact zone with carbonates (T 3 b ); ③stratiform\|like oxidized Cu ore between T 3 b carbonate rocks and T 3 j hornstones; ④brecciated Cu ore at the local periphery of porphyry; and ⑤vein Pb\|Zn\|Ag ore in the outer contact zone. They constitute a unique integrated polymetal mineralization series of epigenetic intermediate\|acid magmatic hydrothermal system.Studies have shown that the Yulong deposit was the coupling product of sedimentation, magmatism, and tectonism. The Cu\|bearing sandstones in the Japila Formation have provided partial ore\|bearing materials for the porphyry mineralization during the Himalayan period. The mineralized porphyry mass was passively emplaced and controlled by a nose\|like anticlinal trap opening to the north. The interlayered fractured zone formed during folding between the Jiapila and Bolila Formations acted as favorable host space for stratiform\|like skarn and oxidized ores. A large number of cleavages and fissures developed during folding provided both conduits for the circulation of ore\|forming fluids and host spaces for Pb\|Zn\|Ag ore veins. The veinlet\|disseminated Cu\|Mo ore in the porphyry mass owns the characteristics of typical porphyry copper deposits in the world. The veinlet\|disseminated ore body and the stratiform\|like skarn\|type and/or oxidized ore body, the two main ore bodies in Yulong, are connected with each other and shown as “mushroom\|like" shape, in which the former occurs as “mushroom stem" and the latter as “mushroom cover".展开更多
Multistage tungsten mineralization was recently discovered in the Mamupu copper-polymetallic deposit in the southern Yulong porphyry copper belt(YPCB),Tibet.This study reports the results of cathodoluminescence,trace ...Multistage tungsten mineralization was recently discovered in the Mamupu copper-polymetallic deposit in the southern Yulong porphyry copper belt(YPCB),Tibet.This study reports the results of cathodoluminescence,trace element and Sr isotope analyses of Mamupu scheelite samples,undertaken in order to better constrain the mechanism of W mineralization and the sources of the ore-forming fluids.Three different types of scheelite are identified in the Mamupu deposit:scheelite A(Sch A)mainly occurs in breccias during the prograde stage,scheelite B(Sch B)forms in the chlorite-epidote alteration zone in the retrograde stage,while scheelite C(Sch C)occurs in distal quartz sulfide veins.The extremely high Mo content and negative Eu anomaly in Sch A represent high oxygen fugacity in the prograde stage.Compared with ore-related porphyries,Sch A has a similar REE pattern,but with higher ΣREE,more depleted HREE and slightly lower(^(87)Sr/^(86)Sr)i ratios.These features suggest that Sch A is genetically related to ore-related porphyries,but extensive interaction with carbonate surrounding rocks affects the final REE and Sr isotopic composition.Sch B shows dark(Sch B-I)and light(Sch B-II)domains under CL imaging.From Sch B-I to Sch B-II,LREEs are gradually depleted,with MREEs being gradually enriched.Sch C has the highest LREE/HREE ratio,which indicates that it inherited the geochemical characteristics of fluids after the precipitation of HREE-rich minerals,such as diopside and garnet,in the early prograde stage.The Mo content in Sch B and Sch C gradually decreased,indicating that the oxygen fugacity of the fluids changed from oxidative in the early stages to reductive in the later,the turbulent Eu anomaly in Sch B and Sch C indicating that the Eu anomaly in the Mamupu scheelite is not solely controlled by oxygen fugacity.The extensive interaction of magmatic-hydrothermal fluids and carbonate provides the necessary Ca^(2+)for the precipitation of scheelite in the Mamupu deposit.展开更多
Extending in a NNW-SSE direction. the Yulong porphyry copper belt is the largest and richest porphyry copper belt in China, originating in the Paleogene. Tectonically located on the eastern margin of the northern Tibe...Extending in a NNW-SSE direction. the Yulong porphyry copper belt is the largest and richest porphyry copper belt in China, originating in the Paleogene. Tectonically located on the eastern margin of the northern Tibet geodepression. and nearly 500 km of the Himalayan Yarlung Zangbo plate subduction zone of nearly E-W trend. it is a relatively typical intracontinental rejuvenated platform-type porphyry copper belt. Ore-bearing porphyry masses in the belt mainly represented by monzogranite-porphyry occurring as stocks in variegated sandshale of the lower Upper Triassic Jiapila Fromation and its overlying and underlying copper-bearing strata. They are characterized by enrichment in K. CI and LREE. abundant fluid inclusions and a distinct porphyroblastic texture. The oxygen. hydrogen. strotium. lead and sulfur isotopic values of the rock show the feature of crust-mantle mixing.The Orebodies are plpe-shaped stratoid; the mineralization is dominated by Cu and Mo, accompanied by Fe. Co. Au. Ag. Bi. W. Pb. Zn. and Pt-group elements. Alteration is strong. marked mainly by potassic alteration, silicification. skarnization and propylitization. The formation of this type of deposit largely progressed through two stages. The first stage was the stage of formation of Cu-bearing source beds. It occurred in the Triassic. when a transgressive copper-bearing formation was deposited on the western margin of the Qamdo Bay. which was represented by intermediate-acid volcanic rocks and variegated sandshale in the lower part. dolomitic carbonate rocks in the middle and black carbonaceous sandshale in the upper part. In the second stage. composite porphyry copper deposits were formed. This stage took place in the Paleogene. when this district was in a stage of platform rejuvenation. forming a series of NNW-trending deep faults. so that Na, K. Cl. H2O and CO2-rich hydrothermal fluids from the depths were injected into the upper crust and replaced and melted copper-bearing sialic rocks of the upper crust. e. g. the Triassic copper-bearing rock series in the Yulong area. to form porphyroblastic cooper-bearing intermediate-acid porphyry.展开更多
The Gangdise plutonic\|volcanic arc is situated in the eastern section of the Tethys\|Himalaya metallogenic province. It is acknowledged as a “tectonic\|magmatic complex" because of its well\|developed fault and...The Gangdise plutonic\|volcanic arc is situated in the eastern section of the Tethys\|Himalaya metallogenic province. It is acknowledged as a “tectonic\|magmatic complex" because of its well\|developed fault and igneous activities. Intermediate to acid plutons and dikes were mainly emplaced in the Upper Cretaceous to Lower Eocene volcanic rocks. The unique tectonic position and extremely complicated evolution history of the Gangdise arc have given rise to favorable conditions for polymetal mineralization. From Xietongmen in the west to Mozhugongka in the east of the arc, Au, Cu, Pb, Zn, and Ag show large ore\|forming potentials with well overlapped and highly intensified polymetal anomalies. In the arc region, many localities, like Jiama (Cu, Pb, Zn, Au, Ag) and Qulong (Cu, Pb, Zn) in Mozhugongka county, Lakang’e (Cu, Pb, Zn, Mo) in Lazi county, Tinggong (Cu, Mo) and Chongjiang (Cu, Mo) in Nimu county, Dabu (Cu, Au) in Qushui county, and Dongga (Au, Cu) in Xietongmen county, have sound prospective for polymetals.展开更多
蚀变分带和成矿机制的准确厘定是建立斑岩成矿模型与找矿预测的关键。本文以新生代金沙江-哀牢山成矿带的玉龙斑岩铜矿为例,通过质量作用定律(LMA)和吉布斯自由能最小化模型(GEM),构建含矿热液与斑岩侵入体的pH-f O 2相图和动态传输模型...蚀变分带和成矿机制的准确厘定是建立斑岩成矿模型与找矿预测的关键。本文以新生代金沙江-哀牢山成矿带的玉龙斑岩铜矿为例,通过质量作用定律(LMA)和吉布斯自由能最小化模型(GEM),构建含矿热液与斑岩侵入体的pH-f O 2相图和动态传输模型,以揭示蚀变分带成因和金属成矿机制。LMA与GEM结果显示初始成矿流体pH值为4.7,logf_(O2)=-23.0(ΔFMQ=+2.7),且溶解Cu含量为1138×10^(-6),Mo为1.2×10^(-6)。研究表明,当该酸性及强氧化性流体流入二长花岗斑岩体时,在温度为450~360℃范围内,代表钾硅酸盐化蚀变的钾长石、黑云母、硬石膏、赤铁矿和磁铁矿的矿物逐渐沉淀,且与钾硅酸盐化蚀变相关流体具有较高pH值(5.0~7.0)和氧逸度(ΔFMQ=+2.9~+3.6)特征;当温度在360~320℃范围时,代表青磐岩化蚀变阶段的典型矿物如绿帘石、铁绿泥石和斜绿泥石等逐渐形成,流体pH值(5.0~6.4)和氧逸度(ΔFMQ=+1.1)均有所下降;当温度进一步从320℃下降到200℃时,流体pH值(5.0~5.7)进一步小幅下降,而氧逸度则(ΔFMQ=+1.7)略有回升,在此期间,绢云母和方解石等开始沉淀并形成典型的绢英岩化蚀变。此外,以HMoO_(4)^(-)和MoO_(4)^(2-)为载体的Mo在狭窄高温区间(450~370℃)内沉淀,而以CuCl(CuCl_(4)^(3-)、CuCl_(2)^(-)、CuCl)为主要载体的Cu则在在中、高温(450~300℃)范围中沉淀。通过利用LMA反演及GEM正演相结合定量化地刻画了玉龙斑岩铜矿水岩反应过程,由此揭示了斑岩矿床蚀变分带是逐渐冷却的单一岩浆热液与斑岩体不断反应的结果,且不同温度窗口对应着钾硅酸盐化(450~360℃)、青磐岩化(360~320℃)和绢英岩化(320~200℃)蚀变矿物的形成,故含矿流体温度的快速下降可能是玉龙铜矿蚀变叠加的重要因素。此外,Cu、Mo络合离子溶解度对温度变化的差异响应,导致了Mo矿化主要发育于靠近斑岩体的高温区域,而Cu则以网脉状-浸染状叠加到Mo矿化之上,并广泛分布于斑岩体周边的高-中温区域。展开更多
通过对王龙斑岩铜矿石英斑晶、辉钼矿石英脉中流体包裹体岩相学、包裹体显微测温分析、包裹体成分的激光拉曼探针分析及包裹体中子矿物的扫描电镜/能谱分析,发现矿化斑岩石英斑晶中发育多期流体包裹体。斑晶中除流体包裹体外尚可见少量...通过对王龙斑岩铜矿石英斑晶、辉钼矿石英脉中流体包裹体岩相学、包裹体显微测温分析、包裹体成分的激光拉曼探针分析及包裹体中子矿物的扫描电镜/能谱分析,发现矿化斑岩石英斑晶中发育多期流体包裹体。斑晶中除流体包裹体外尚可见少量熔体包裹体,与斑岩期矿化有关的成矿流体以中高温(200～537℃)、高盐度(29.6～44.7 wt%NaCleq)为特征,与粘土化蚀变有关的流体包裹体以低温、富 Ca 为特征,不同气相充填度的气液两相包裹体与高盐度含子矿物多相包裹体共存,且具有相似的均一温度,显示不混溶流体包裹体特征。温度、压力降低引起的流体不混溶是造成斑岩型矿化矿质沉淀的主要因素,斑岩期流体与浅成低温热液期流体形成于统一的流体系统,为同源演化结果。展开更多
基金supported by the Research Project of Shengyuan Mining Group Co.Ltd,Tibet(Grant No.XZSYKYJT-JSFW-2019-001)the Basic Research Fund of Institute of mineral Resource,Chinese Academy of Geological Sciences(Grant Nos.KJ2102,KK2116,KK2017)+2 种基金the National Natural Science Foundation of China(Grant No.41902097)the Science and Technology Plan Project of the Tibetan Autonomous Region(Grant No.XZ201901-GB-24)Geological Survey project(Grant No.DD20190167)。
文摘The Mamupu skarn-type Cu-Au polymetallic deposit represents the first discovery of a medium deposit in the southern Yulong porphyry copper belt(YPCB),eastern Tibet.The Cu-Au mineralization mainly occurs as chalcopyrite in breccia,within the plate-like carbonate interlayer,being closely related to chloritization(e.g.,chlorite,magnetite and epidote)and skarnization(e.g.,diopside,tremolite and garnet).The ore-related quartz syenite porphyry(QSP)and granodiorite porphyry(GP)were emplaced at 40.1±0.2 Ma and 39.9±0.3 Ma,respectively.The QSP of Mamupu is an alkaline-rich intrusion,relatively enriched in LREE,LILE,depleted in HFSE,with no significant negative Eu and Ce anomalies,slightly high(^(87)Sr/^(86)Sr)i,lowε_(Nd)(t),uniform(^(206)Pb/^(204)Pb)i andε_(Hf)(t)values,which indicates that the porphyry magma may be caused by both the mixing of metasomatized EM II enriched mantle and thickened juvenile lower crust.The QSP in the Mamupu deposit shares a similar genesis of petrology to other ore-related porphyries within the YPCB.High oxygen fugacity and water content of the magmas are essential for the formation of porphyry and skarn Cu deposits.The QSP has similar high magmatic oxidation states and water content to the Yulong deposit,which indicates that the Mamupu has a high prospecting potential.Differences in the geological characteristics and scale of mineralization between the Mamupu and other YPCB deposits may be due to the different emplacement depths of ore-related intrusions,as well as differences in the surrounding rocks.
文摘The Oyu Tolgoi cluster of seven porphyry Cu-Au-Mo deposits in southern Mongolia,define a narrow,linear,12 km long,almost continuously mineralised trend,which contains in excess of 42 Mt of Cu and1850 t of Au,and is among the largest high grade porphyry Cu-Au deposits in the world.These deposits lie within the Gurvansayhan island-arc terrane,a fault bounded segment of the broader Silurian to Carboniferous Kazakh-Mongol arc,located towards the southern margin of the Central Asian Orogenic Belt,a collage of magmatic arcs that were periodically active from the late Neoproterozoic to PermoTriassic,extending from the Urals Mountains to the Pacific Ocean.Mineralisation at Oyu Tolgoi is associated with multiple,overlapping,intrusions of late Devonian（～372 to 370 Ma） quartzmonzodiorite intruding Devonian（or older） juvenile,probably intra-oceanic arc-related,basaltic lavas and lesser volcaniclastic rocks,unconformably overlain by late Devonian（～370 Ma） basaltic to dacitic pyroclastic and volcano sedimentary rocks.These quartz-monzodiorite intrusions range from earlymineral porphyritic dykes,to larger,linear,syn-,late- and post-mineral dykes and stocks.Ore was deposited within syn-mineral quartz-monzodiorites,but is dominantly hosted by augite basalts and to a lesser degree by overlying dacitic pyroclastic rocks.Following ore deposition,an allochthonous plate of older Devonian（or pre-Devonian） rocks was overthrust and a post-ore biotite granodiorite intruded at～365 Ma.Mineralisation is characterised by varying,telescoped stages of intrusion and alteration.Early A-type quartz veined dykes were followed by Cu-Au mineralisation associated with potassic alteration,mainly K-feldspar in quartz-monzodiorite and biotite-magnetite in basaltic hosts.Downward reflux of cooled,late-magmatic hydrothermal fluid resulted in intense quartz-sericite retrograde alteration in the upper parts of the main syn-mineral intrusions,and an equivalent chlorite-muscovite/illite-hematite assemblage in basaltic host rocks.Uplift,facilitated by syn-mineral longitudinal faulting,brought sections of the porphyry deposit to shallower depths,to be overprinted and upgraded by late stage,shallower,advanced argillic alteration and high sulphidation mineralisation.Key controls on the location,size and grade of the deposit cluster include（i） a long-lived,narrow faulted corridor;（ii） multiple pulses of overlapping intrusion within the same structure;and（iii） enclosing reactive,mafic dominated wall rocks,focussing ore.
文摘The Yulong supper\|large copper deposit is situated within the well\|known S\|N striking Yulong copper\|molybdenum ore belt. The ore\|bearing biotite\|monogranitic porphyry was emplaced within clastic rocks (mainly shales and siltstones) of the Jiapila Formation (T 3 j ) and carbonate rocks of the Bolila Formation (T 3 b ) of the Upper Triassic. Five mineralization patterns have been recognized in the deposit, i.e., ①veinlet\|disseminated Cu\|Mo ore in the porphyry; ②skarn\|type Cu ore at the contact zone with carbonates (T 3 b ); ③stratiform\|like oxidized Cu ore between T 3 b carbonate rocks and T 3 j hornstones; ④brecciated Cu ore at the local periphery of porphyry; and ⑤vein Pb\|Zn\|Ag ore in the outer contact zone. They constitute a unique integrated polymetal mineralization series of epigenetic intermediate\|acid magmatic hydrothermal system.Studies have shown that the Yulong deposit was the coupling product of sedimentation, magmatism, and tectonism. The Cu\|bearing sandstones in the Japila Formation have provided partial ore\|bearing materials for the porphyry mineralization during the Himalayan period. The mineralized porphyry mass was passively emplaced and controlled by a nose\|like anticlinal trap opening to the north. The interlayered fractured zone formed during folding between the Jiapila and Bolila Formations acted as favorable host space for stratiform\|like skarn and oxidized ores. A large number of cleavages and fissures developed during folding provided both conduits for the circulation of ore\|forming fluids and host spaces for Pb\|Zn\|Ag ore veins. The veinlet\|disseminated Cu\|Mo ore in the porphyry mass owns the characteristics of typical porphyry copper deposits in the world. The veinlet\|disseminated ore body and the stratiform\|like skarn\|type and/or oxidized ore body, the two main ore bodies in Yulong, are connected with each other and shown as “mushroom\|like" shape, in which the former occurs as “mushroom stem" and the latter as “mushroom cover".
基金jointly supported by the National Key Research and Development Program of China(Grant No.2022YFC2905001)the Basic Research Fund of the Chinese Academy of Geological Sciences(Grant No.JKYZD202316)+2 种基金the National Natural Science Foundation of China(Grant Nos.42272093,42230813,42002097)the Research Project of the Shengyuan Mining Co.,Ltd.,Tibet(Grant No.XZSYKYJT-JSFW2019-001)the China Scholarship Council project and the Geological Survey project(Grant Nos.DD20230054,DD20221684,DD20221690,DD20230031,DD20230049,DD20230338)。
文摘Multistage tungsten mineralization was recently discovered in the Mamupu copper-polymetallic deposit in the southern Yulong porphyry copper belt(YPCB),Tibet.This study reports the results of cathodoluminescence,trace element and Sr isotope analyses of Mamupu scheelite samples,undertaken in order to better constrain the mechanism of W mineralization and the sources of the ore-forming fluids.Three different types of scheelite are identified in the Mamupu deposit:scheelite A(Sch A)mainly occurs in breccias during the prograde stage,scheelite B(Sch B)forms in the chlorite-epidote alteration zone in the retrograde stage,while scheelite C(Sch C)occurs in distal quartz sulfide veins.The extremely high Mo content and negative Eu anomaly in Sch A represent high oxygen fugacity in the prograde stage.Compared with ore-related porphyries,Sch A has a similar REE pattern,but with higher ΣREE,more depleted HREE and slightly lower(^(87)Sr/^(86)Sr)i ratios.These features suggest that Sch A is genetically related to ore-related porphyries,but extensive interaction with carbonate surrounding rocks affects the final REE and Sr isotopic composition.Sch B shows dark(Sch B-I)and light(Sch B-II)domains under CL imaging.From Sch B-I to Sch B-II,LREEs are gradually depleted,with MREEs being gradually enriched.Sch C has the highest LREE/HREE ratio,which indicates that it inherited the geochemical characteristics of fluids after the precipitation of HREE-rich minerals,such as diopside and garnet,in the early prograde stage.The Mo content in Sch B and Sch C gradually decreased,indicating that the oxygen fugacity of the fluids changed from oxidative in the early stages to reductive in the later,the turbulent Eu anomaly in Sch B and Sch C indicating that the Eu anomaly in the Mamupu scheelite is not solely controlled by oxygen fugacity.The extensive interaction of magmatic-hydrothermal fluids and carbonate provides the necessary Ca^(2+)for the precipitation of scheelite in the Mamupu deposit.
文摘Extending in a NNW-SSE direction. the Yulong porphyry copper belt is the largest and richest porphyry copper belt in China, originating in the Paleogene. Tectonically located on the eastern margin of the northern Tibet geodepression. and nearly 500 km of the Himalayan Yarlung Zangbo plate subduction zone of nearly E-W trend. it is a relatively typical intracontinental rejuvenated platform-type porphyry copper belt. Ore-bearing porphyry masses in the belt mainly represented by monzogranite-porphyry occurring as stocks in variegated sandshale of the lower Upper Triassic Jiapila Fromation and its overlying and underlying copper-bearing strata. They are characterized by enrichment in K. CI and LREE. abundant fluid inclusions and a distinct porphyroblastic texture. The oxygen. hydrogen. strotium. lead and sulfur isotopic values of the rock show the feature of crust-mantle mixing.The Orebodies are plpe-shaped stratoid; the mineralization is dominated by Cu and Mo, accompanied by Fe. Co. Au. Ag. Bi. W. Pb. Zn. and Pt-group elements. Alteration is strong. marked mainly by potassic alteration, silicification. skarnization and propylitization. The formation of this type of deposit largely progressed through two stages. The first stage was the stage of formation of Cu-bearing source beds. It occurred in the Triassic. when a transgressive copper-bearing formation was deposited on the western margin of the Qamdo Bay. which was represented by intermediate-acid volcanic rocks and variegated sandshale in the lower part. dolomitic carbonate rocks in the middle and black carbonaceous sandshale in the upper part. In the second stage. composite porphyry copper deposits were formed. This stage took place in the Paleogene. when this district was in a stage of platform rejuvenation. forming a series of NNW-trending deep faults. so that Na, K. Cl. H2O and CO2-rich hydrothermal fluids from the depths were injected into the upper crust and replaced and melted copper-bearing sialic rocks of the upper crust. e. g. the Triassic copper-bearing rock series in the Yulong area. to form porphyroblastic cooper-bearing intermediate-acid porphyry.
文摘The Gangdise plutonic\|volcanic arc is situated in the eastern section of the Tethys\|Himalaya metallogenic province. It is acknowledged as a “tectonic\|magmatic complex" because of its well\|developed fault and igneous activities. Intermediate to acid plutons and dikes were mainly emplaced in the Upper Cretaceous to Lower Eocene volcanic rocks. The unique tectonic position and extremely complicated evolution history of the Gangdise arc have given rise to favorable conditions for polymetal mineralization. From Xietongmen in the west to Mozhugongka in the east of the arc, Au, Cu, Pb, Zn, and Ag show large ore\|forming potentials with well overlapped and highly intensified polymetal anomalies. In the arc region, many localities, like Jiama (Cu, Pb, Zn, Au, Ag) and Qulong (Cu, Pb, Zn) in Mozhugongka county, Lakang’e (Cu, Pb, Zn, Mo) in Lazi county, Tinggong (Cu, Mo) and Chongjiang (Cu, Mo) in Nimu county, Dabu (Cu, Au) in Qushui county, and Dongga (Au, Cu) in Xietongmen county, have sound prospective for polymetals.
文摘蚀变分带和成矿机制的准确厘定是建立斑岩成矿模型与找矿预测的关键。本文以新生代金沙江-哀牢山成矿带的玉龙斑岩铜矿为例,通过质量作用定律(LMA)和吉布斯自由能最小化模型(GEM),构建含矿热液与斑岩侵入体的pH-f O 2相图和动态传输模型,以揭示蚀变分带成因和金属成矿机制。LMA与GEM结果显示初始成矿流体pH值为4.7,logf_(O2)=-23.0(ΔFMQ=+2.7),且溶解Cu含量为1138×10^(-6),Mo为1.2×10^(-6)。研究表明,当该酸性及强氧化性流体流入二长花岗斑岩体时,在温度为450~360℃范围内,代表钾硅酸盐化蚀变的钾长石、黑云母、硬石膏、赤铁矿和磁铁矿的矿物逐渐沉淀,且与钾硅酸盐化蚀变相关流体具有较高pH值(5.0~7.0)和氧逸度(ΔFMQ=+2.9~+3.6)特征;当温度在360~320℃范围时,代表青磐岩化蚀变阶段的典型矿物如绿帘石、铁绿泥石和斜绿泥石等逐渐形成,流体pH值(5.0~6.4)和氧逸度(ΔFMQ=+1.1)均有所下降;当温度进一步从320℃下降到200℃时,流体pH值(5.0~5.7)进一步小幅下降,而氧逸度则(ΔFMQ=+1.7)略有回升,在此期间,绢云母和方解石等开始沉淀并形成典型的绢英岩化蚀变。此外,以HMoO_(4)^(-)和MoO_(4)^(2-)为载体的Mo在狭窄高温区间(450~370℃)内沉淀,而以CuCl(CuCl_(4)^(3-)、CuCl_(2)^(-)、CuCl)为主要载体的Cu则在在中、高温(450~300℃)范围中沉淀。通过利用LMA反演及GEM正演相结合定量化地刻画了玉龙斑岩铜矿水岩反应过程,由此揭示了斑岩矿床蚀变分带是逐渐冷却的单一岩浆热液与斑岩体不断反应的结果,且不同温度窗口对应着钾硅酸盐化(450~360℃)、青磐岩化(360~320℃)和绢英岩化(320~200℃)蚀变矿物的形成,故含矿流体温度的快速下降可能是玉龙铜矿蚀变叠加的重要因素。此外,Cu、Mo络合离子溶解度对温度变化的差异响应,导致了Mo矿化主要发育于靠近斑岩体的高温区域,而Cu则以网脉状-浸染状叠加到Mo矿化之上,并广泛分布于斑岩体周边的高-中温区域。
文摘通过对王龙斑岩铜矿石英斑晶、辉钼矿石英脉中流体包裹体岩相学、包裹体显微测温分析、包裹体成分的激光拉曼探针分析及包裹体中子矿物的扫描电镜/能谱分析,发现矿化斑岩石英斑晶中发育多期流体包裹体。斑晶中除流体包裹体外尚可见少量熔体包裹体,与斑岩期矿化有关的成矿流体以中高温(200～537℃)、高盐度(29.6～44.7 wt%NaCleq)为特征,与粘土化蚀变有关的流体包裹体以低温、富 Ca 为特征,不同气相充填度的气液两相包裹体与高盐度含子矿物多相包裹体共存,且具有相似的均一温度,显示不混溶流体包裹体特征。温度、压力降低引起的流体不混溶是造成斑岩型矿化矿质沉淀的主要因素,斑岩期流体与浅成低温热液期流体形成于统一的流体系统,为同源演化结果。
