祁连山东段的元古宙陇山群

陇山群是从祁连山东段原“牛头河群”哑岩系下部分解出来的变质岩系，它包括从下到上的大理岩和片麻岩两个岩组。依其片麻岩组先后同位素年代学的研究，主要最早一组年龄值为８１３－８１１Ｍａ，相当中－上元古代。作者从该岩群的出露和展布，认为在构造体系上，它属祁连山带的基底隆起部分，并讨论了赋存在片麻岩组内陈家调铁铜矿床的特征及其地质意义。     

印支运动在鄂尔多斯盆地和四川盆地启动时间的讨论：来自生长地层的证据

造山带的形成、演化与周缘盆地受统一构造事件影响,"盆"与"山"在构造和沉积方面相互耦合,沉积盆地存在造山事件的响应,如生长地层、包卷层理等。生长地层为同构造或同变形阶段沉积,其沉积时代可以有效约束构造事件时代。中央造山带近东西向展布,北侧为鄂尔多斯地块,南侧为扬子地块。中央造山带的形成主要源于原—古特提斯洋的闭合,原特提斯洋在早古生代闭合,古特提斯洋在中生代闭合,后者改造前者并响应全球印支运动。印支运动的启动,一方面促使现今中国大陆雏形的形成,另一方面响应Pangea超大陆的最终汇聚,具有重要的大地构造意义。古特提斯洋闭合,华南地块和华北地块汇聚拼贴,并在鄂尔多斯盆地和四川盆地沉积地层中保留了很好的记录。笔者在鄂尔多斯盆地南缘上三叠统识别出一套生长地层,通过最年轻碎屑锆石与区内相同地层凝灰岩锆石对比,限定印支运动启动时间为233 Ma左右;在四川盆地北缘上三叠统须家河组识别出一套生长地层,通过对比分析,推测印支运动启动时间为216 Ma左右。     

湖北竹山县银洞沟矿床成矿流体特征及矿床成因

银洞沟大型银多金属矿床位于南秦岭造山带,矿体主要受东西向的银洞岩背斜控制,呈脉状产于武当山群变火山岩.热液成矿作用包含4个阶段:(Ⅰ)细粒石英-闪锌矿-方铅矿阶段;(Ⅱ)细粒石英-银金矿化阶段;(Ⅲ)粗粒石英阶段,含少量方铅矿-闪锌矿-黄铜矿;(Ⅳ)块状铁白云石-石英阶段.银洞沟矿床流体包裹体可分为3类:NaCl-H2O型(W型)、CO2-H2O-NaCl型(C型)和CO2-CH4型(PC型).Ⅰ阶段石英中的流体包裹体以W和C型为主,含少量PC型,相比Ⅰ阶段,Ⅱ阶段的C型包裹体更多,而Ⅲ阶段仅发育W型包裹体.显微测温表明,Ⅰ阶段流体包裹体均一温度为308 ～ 436℃,盐度为5.1％～10.2％ NaCleqv;Ⅱ阶段均一温度为220～375℃,盐度为2.0％～ 10.7％ NaCleqv;Ⅲ阶段均一温度为122 ～272℃,盐度为0.4％～7.2％ NaCleqv.根据C型包裹体估算前两个阶段压力分别为330 ～463MPa和180～363MPa,相应成矿深度分别为12.5～17.5km和6.8 ～13.8km.从Ⅰ到Ⅲ阶段,δ18OW、δD平均值分别由8.4‰和-72‰,变化至0.9‰和-67‰,指示初始成矿流体来自变质热液,晚阶段混入了大气降水.流体包裹体与氢氧同位素数据表明,银洞沟矿床成矿流体为中温、低盐度、富CO2的变质热液,属于造山型矿床,流体的混合可能是金属沉淀的主要机制.     

汇聚造山带变质矿物冠状反应边及生长环带

哀牢山、澜沧江、高黎贡山、念青唐古拉山等汇聚造山带变质岩中,发现一些标型或特征变质矿物间形成冠状反应边或生长环带。它们是变质过程的真实记录,反映了变形变质环境条件的不断变化,完整或直观地表现了不同地体或构造带PTt轨迹特征。可帮助恢复汇聚造山带中不同地体构造属性,为研究造山带PTtD轨迹和PTDX轨迹,提供准确资料。可从另一侧面了解汇聚造山带的演化史。     

The Shanggong gold deposit, Eastern Qinling Orogen, China: Isotope geochemistry and implications for ore genesis

The Shanggong Au deposit in the Xiong’er Terrane, East Qinling, China, has resources of about 30 ton Au, making it one of the largest orogenic-mesothermal Au deposits hosted in volcanic rocks of the Mesoproterozoic Xiong’er Group. Three stages of hydrothermal activity are recognized (early, middle and late), of which two (early and middle) were ore producing and characterized by quartz–pyrite and polymetallic sulfides, respectively. The third and late stage is represented by a carbonate–quartz assemblage. Hydrogen, oxygen and carbon isotope systematics of the Shanggong deposit from a previous work suggest that the early stage fluids were derived from magmatic and/or metamorphic devolatilization of sedimentary rocks at depth. This is supported by new C, S and published Sr and Pb isotopic data, presented in this paper. These new data, δ¹³C values ranging from 1.5 ‰ for early stage ankerite to −2.2 ‰ for late stage ankerite, negative δ³⁴S values for sulfides from the middle stage (–19.2 to –6.3 ‰), suggest a contribution from organic matter and that the ore fluid evolved from deeply sourced to shallowly sourced, with those of the middle stage representing a mixture of these two fluid systems. The comparison of the hydrogen–oxygen–carbon–sulfur–lead–strontium isotope systematics between the Shanggong deposit and the main lithologies in the Xiong’er Terrane, shows that neither these nor the underlying lower crust and mantle, or combinations thereof, could be considered as the source of ore fluids for the Shanggong Au deposit. A likely source was a carbonaceous carbonate, sandstone, shale, chert sequence in the underthrusted Guandaokou and Luanchuan Groups, exposed south of the Xiong’er Terrane.Ar–Ar and Rb–Sr isochron ages for mineral phases of the early, middle and late stages, together with geological field data, constrain the timing of the hydrothermal activity and Au metallogenesis at 242 ± 10, 167 ± 7 and 112 ± 7 Ma, respectively. This metallogenesis and associated granitic magmatism, can be related to the continental collision between the Yangtze and North China Cratons that resulted in the formation of the Qinling Orogen, led to the different hydrothermal systems that were responsible for the three stages that formed the Shanggong Au deposit, over a period of about 130 Myrs.     

阿尔泰造山带变质岩系时代问题的讨论

针对目前阿尔泰地区变质岩系时代划分中年龄数据应用的一些问题,提出如下认识:富蕴县城西的石榴石片麻岩中锆石UPb上交点年龄2349±226Ma(2σ),初步确证了该区古元古代大陆地壳岩石的存在;克木齐群和富蕴群变质岩全岩SmNd等时线年龄代表其母岩形成时代。变质岩系和显生宙花岗岩类的Nd模式年龄,以及各种类型岩石中长石Pb二阶段模式t1年龄仅指出存在前寒武纪大陆地壳的可能性,没有真正的年龄意义,不能作为划分地层时代的依据。阿尔泰造山带是否存在1400Ma和700～900Ma的变质岩系岩石,至今仍缺乏可靠年龄数据的佐证     

哀牢山造山带构造演化

哀牢山造山带造山活动始于晚二叠世的扬子陆块被动边缘的裂谷环境,经过印支及喜马拉雅期两次造山作用,形成了四个构造世代的叠加构造变形。这些不同时期的构造共生组合,既表现出陆内造山带垂向上不同构造层次构造环境的流变学特征,又反映了造山物质从表部下冲到地壳深处,又折返地表的复杂经历。清晰地刻划出哀牢山造山带的所经历的陆内俯冲、主期碰撞造山及后期卷入喜马拉雅造山活动的发展过程。     

河南鱼池岭钼矿床辉钼矿铼-锇同位素年龄及地质意义

河南嵩县鱼池岭钼矿床是东秦岭钼矿带新发现的大型斑岩钼矿床,产于被前人认为白垩纪的合峪花岗岩基内部。鱼池岭矿床5件辉钼矿样品的铼锇同位素模式年龄介于(134.3±2.0)~(141.8±1.6)Ma 之间,铼锇等时线年龄为144.3±5.2Ma（1σ,MSWD=3.7）。据此,结合前人获得的年龄资料,确定合峪复式花岗岩基的岩浆侵入序列为：(1) 144Ma之前的似斑状黑云母二长花岗岩,(2) 144Ma左右的黑云母二长花岗斑岩,(3) 136~127Ma左右的巨斑状黑云母二长花岗斑岩,(4) <127Ma的(石英)正长斑岩脉或岩株;合峪复式花岗岩基形成于晚侏罗世—早白垩世,而非前人认为的仅限于白垩纪;成岩成矿构造背景为碰撞加厚的造山带地壳和岩石圈的伸展减薄或减压增温体制,岩浆侵入和成矿作用与地壳快速隆升事件相伴随。     

Re-Os and U-Pb Geochronology of the Erlihe Pb-Zn Deposit,Qinling Orogenic Belt,Central China,and Constraints on Its Deposit Genesis

The Erlihe Pb-Zn deposit is an important mine of the Pb-Zn metallogenic zone in the South Qinling Orogen.It has been considered a sedimentary exhalative deposit in previous investigations because the ore body occurs concordantly at the transitional location of an upright fold.Re and Os isotopic analyses for paragenetic pyrites with sphalerite and galena from the ore body have been used to determine the timing of mineralization and to trace the source of metallogenic materials.The Re-Os isotopic data of f...     

西秦岭造山带三叠纪大规模成矿作用背景: 来自恰冬铜矿高镁安山岩的证据

西秦岭造山带广泛发育与三叠纪岩浆活动密切相关的金、铜、钼等多金属矿床, 表明该地区存在一期三叠纪大规模成矿事件, 但其成矿地球动力学背景一直存在争议。恰冬铜矿是西秦岭造山带内与早三叠世高镁安山岩有关的铜矿床。本文对高镁安山岩开展了锆石U-Pb年代学、岩石地球化学和Sr-Nd-Hf同位素分析, 对其岩石成因及构造环境进行了探讨, 以进一步约束西秦岭造山带三叠纪大规模成矿作用的地球动力学背景。安山岩的锆石U-Pb年龄为246.1±1.6Ma, 形成于早三叠世。岩石属于高钾钙碱性-钙碱性系列, SiO₂含量为54.60% ~56.21%, 具有较高的MgO含量(3.78%~4.57%)和Mg^#(49.7~62.1), 与日本Setouchi火山岩带中典型赞岐岩相类似。安山岩富集轻稀土元素(LREE)和Cs、Rb、U、Sr等大离子亲石元素(LILEs), 显著亏损Nb、Ta、Ti、P等高场强元素(HFSEs), 其初始⁸⁷Sr/⁸⁶Sr比值、ε_Nd(t)值和锆石ε_Hf(t)值分别为0.7073~0.7090、-9.72~-11.03和-2.1~-18.6, 是俯冲沉积物熔融产生的熔体与地幔楔发生交代反应的产物, 并经历了一定程度的结晶分异。以上研究表明, 恰冬铜矿高镁安山岩形成于早三叠世古特提斯洋俯冲背景下的活动大陆边缘环境。结合区域成矿资料分析, 西秦岭造山带在早-中三叠世处于洋壳俯冲环境, 发育岩浆-热液成矿系统。