内蒙古东北部得耳布尔铅锌银矿床闪锌矿Rb-Sr年龄及地质意义

得耳布尔铅锌银矿床产出于内蒙古东北部额尔古纳地块中部,得尔布干断裂西北侧。矿石呈角砾状、团块状产出,尤以闪锌矿粗大集合体与方铅矿伴生为特征。本次研究在对矿石开展矿相学研究基础上,选取成矿早阶段未遭受构造活动影响的8件闪锌矿样品进行Rb-Sr同位素分析,结果显示,8件样品~(87)Rb/~(86)Sr和~(87)Sr/~(86)Sr同位素比值分别在0.0824~8.957和0.712 902~0.730 753之间,二者之间具线性关系,8件样品构成等时线年龄为(144±13)Ma,剔除2件偏离等时线较远样品数据后,获得等时线年龄为(141.6±1.9)Ma(MSWD=1.8)。矿床形成于早白垩世,与额尔古纳地块内其他铅锌银矿床时代基本一致。额尔古纳地块中生代成矿作用直接受控于蒙古-鄂霍茨克造山过程,造山带后碰撞阶段局部拉伸环境引发晚侏罗世—早白垩世浅成岩浆侵入活动,得耳布尔铅锌银矿床的形成与之相关。     

贵州铜仁塘边铅锌矿床成矿时代和成矿物质来源——来自Rb-Sr同位素测年和S-Pb同位素的证据

对贵州铜仁塘边铅锌矿床开展闪锌矿Rb-Sr测年和黄铁矿、方铅矿、闪锌矿S、Pb同位素分析,以获得矿区的成矿年龄,探讨其成矿物质来源。塘边铅锌矿床闪锌矿Rb-Sr等时线年龄为477±5Ma(MSWD=1.2),与前人获得的卜口场矿区闪锌矿Rb-Sr等时线年龄486±6Ma在误差范围内一致,表明矿床形成于加里东早期。黄铁矿、方铅矿、闪锌矿S同位素变化于+25.2‰~+36.1‰之间,与湘西—黔东主要铅锌矿床相似,明显富集重硫,认为S可能来源于寒武系海水碳酸盐和/或下伏地层。方铅矿、闪锌矿Pb同位素~(208)Pb/~(204)Pb值为38.389~38.584,~(207)Pb/~(204)Pb值为15.737~15.790,206Pb/~(204)Pb值为18.181~18.217,μ值为9.75~9.86,显示铅主要来源于上地壳。     

Timing of formation of the Hongdonggou Pb-Zn polymetallic ore deposit,Henan Province,China: Evidence from Rb-Sr isotopic dating of sphalerites

The Hongdonggou Pb-Zn polymetallic ore deposit,located in the southwestern part of the Luanchuan Mo-W-Pb-Zn-Ag polymetallic ore mineralization in Henan Province,China,is an important part of the East Qinling metallogenic belt.The orebodies in the deposit,which are vein,bedded and lenticular,are mainly hosted in the syenite porphyry,and formed within the carbonate and clastic rocks of the Yuku and Qiumugou formations partially.The genesis of the deposit has previously been argued to be of hydrothermal-vein type or of skarn-hydrothermal type.In this study,we report the results of Rb-Sr isotopic dating based on sphalerites from the main orebody of the Hongdonggou Pb-Zn polymetallic ore deposit,which yield an isochron age of 135.7 ± 3.2 Ma,constraining the timing of mineralization as early Cretaceous.The age is close to those reported for the Pb-Zn deposits in the Luanchuan ore belt.The(~(87)Sr/~(86)Sr),values of the sphalerites(0.71127 + 0.00010) are lower than that of terrigenous silicates(0.720) and higher than the mantle(0.707),suggesting that the metallogenic components were mainly derived through crust-mantle mixing.Combining the results from this study with those from previous work,we propose that the Hongdonggou Pb-Zn polymetallic ore deposit is a hydrothermal-vein deposit associated with the early Cretaceous tectonothermal event,and the mineralization is controlled by NWand near EW-trending faults in the Luanchuan Mo-W-Pb-Zn-Ag polymetallic ore concentration belt.     

假玄武玻璃年代学研究现状及其地震学指示意义

假玄武玻璃是一种呈暗色的微晶—隐晶质岩石,一般产于古地震断层滑动面,被认为是研究地震活动的＂化石岩＂。经过碎裂岩化或摩擦熔融,假玄武玻璃发育于从地表到岩石圈地幔的整个地震活动区,其年代学研究对于揭示某一地区古地震活动频次及发生规律有重要意义。假玄武玻璃的定年一般采用Rb-Sr、^40Ar-^39Ar、裂变径迹等三种方法,但Sr的扩散性质、假玄武玻璃内部结构和成分的不均一性及其形成高温快速过程中锆石的退火行为等诸多因素,制约了以上三种方法的应用。文中总结了三种方法,分析了其适用范围和局限性,探讨了假玄武玻璃定年研究中最适用的方法和需注意的事项。最后,阐述了假玄武玻璃研究的地震学指示意义。     

Rb-Sr Isotope Dating of Neoproterozoic (Malani Group) Magmatism from Southwest Rajasthan, India: Evidence of Younger Pan-African Thermal Event by Ar-Ar Studies

This paper reports Rb-Sr isotope ages of the Neoproterozoic volcanics, and associated granitoids of the trans-Aravalli belt of northwestern India. All these rocks along with the earlier reported 779±10 Ma old felsic volcanics from Diri, and Gurapratap Singh of Pali district, Rajasthan, constitute the Malani Group. The study indicates that different rock suites belonging to the Malani Group represent a polyphase igneous activity which spanned for about 100 Ma ranging from 780 to 680 Ma. The granitoids of the Malani Group, i.e. peraluminous Jalore type, and peralkaline Siwana type, were emplaced around 730, and 700 Ma ago, respectively. These plutonic suites represent two different magmatic episodes within a short time interval. The initial Sr ratios of these granitoids suggest lower crustal derivation of the magma. The peralkaline granitoids, and the associated peralkaline rhyolites (pantellerites) are coeval, and cogenetic. The ultrapotassic rhyolite exposed at Manihari of Pali district represents the youngest magmatic activity at 681±20 Ma, having a very high initial Sr ratio of 0.7135±0.0033. The high initial Sr ratio of these rocks may be due to incorporation of radiogenic ⁸⁷Sr from the country rock, by assimilation or fusion, into the residual fraction of the magma in the crust which gave rise to other differentiated rocks of the Group.⁴⁰Ar³⁹Ar studies of two Jalore granite samples indicate presence of post crystallisation thermal disturbance between 500550 Ma ago. The timing of this thermal overprinting on the Malani rocks is related to the widespread Pan-African thermo-tectonic event which is witnessed, and magmatically manifested in different part of the Indian shield.     

贵州独山锑矿田石英Rb-Sr定年及矿床地球化学研究

独山锑矿田位于扬子古陆西南缘与雪峰山隆起的嵌接部,是华南锑矿带的重要组成部分.为厘清该矿田锑矿的成因,在总结区域上典型锑矿床地质特征的基础上,开展了石英Rb-Sr定年、流体包裹体和碳、氧同位素分析,并结合前人的氢、氧、硫、铅同位素研究结果,从成矿时代、成矿流体性质及来源、成矿物质来源等方面探讨了成矿作用.分析测试得到石...     

赣南中生代淘锡坑钨矿区花岗岩锆石SHRIMP年龄及石英脉Rb-Sr年龄测定

江西省崇义县淘锡坑钨矿区位于南岭东西向构造带东段与武夷山北东—北北东向构造带南段的复合部位,属于以石英脉型黑钨矿为主的钨多金属矿床。矿床形成与燕山期中酸性岩浆作用有密切关系,石英矿脉受北西向断裂控制,穿切新元古代地层。文章选取钻孔揭露的底部新鲜花岗岩样品2件,用SHRIMP方法测定锆石的结晶年龄,结果分别为(158.7±3.9)Ma和(157.6±3.5)Ma;对3件含黑钨矿石英脉样品中石英的流体包裹体进行了Rb-Sr等时线年龄测定,结果分别为(154±4)Ma、(157±3)Ma和(161±4)Ma。与前人用Re-Os法测定的辉钼矿(154Ma)比较,发现花岗岩的成岩年龄与含矿石英脉、钨矿的形成年龄相同,成岩、成矿作用几乎同时完成。综合前人研究资料,认为南岭地区160~150Ma成岩成矿作用主要分布于南岭中东段,可能与岩石圈大规模伸展的构造动力学背景有关。     

辽宁凡河康庄子组Rb－Sr年龄

康庄子组Ｒｂ－Ｓｒ测年为１５６５±１１０Ｍａ和４８９±７３Ｍａ。前者与华北地层区内相邻地层在年龄上衔接，有利于区域地层划分与对比；后者同关门山铅锌矿床两阶段铅上交点年龄相近，恰佐证关门山铅锌矿床矿化发生的时间。１７９６±７ＭａＳｍ－Ｎｂ等时线年龄，１５６５±１１０ＭａＲｂ－Ｓｒ等时线年龄和１４０２±２１１ＭａＲＬ－Ｓｒ等时线年龄在地层上是衔接的，对区域地层划分与对比具有重要意义。     

河北寿王坟铜矿黄铜矿铷锶同位素年龄测定及其成矿意义

本文以黄铜矿及其共生矿物为定年对象,采用亚样品取样和铷锶等时线定年方法测定了寿王坟铜矿的成矿时代.分析测试获得黄铜矿 黄铁矿单矿物组合的等时线年龄113.6Ma,黄铜矿 夕卡岩组合的等时线年龄112.3Ma和黄铜矿 黄铁矿 夕卡岩组合的等时线年龄115.0Ma.对比同一矿石亚样品,认为河北寿王坟夕卡岩型铜矿成矿时代为111.0Ma.实验表明,采用矿石亚样品取样方法和直接测定金属硫化物单矿物铷-锶同位素年龄可以有效地确定矿床成矿时代.     

湘东地区金矿床矿化年龄的测定及含矿流体来源的示踪——兼论矿床成因类型

文章对江南造山带中段湖南东部地区主要金矿床开展了成矿年龄测定和硫同位素分析。获得该区黄金洞和大洞金矿床矿脉石英流体包裹体Rb-Sr等时线年龄分别为152±13Ma和70±1.3Ma;同时获得黄金洞矿床矿脉硫化物δ34S均值为-6.3‰(主要集中在-4.8‰到-8.6‰之间)、大洞δ34S均值为-9.2‰(主要在-8‰到-10‰之间)、雁林寺δ34S均值为-1.2‰(主要在-2.6‰和6.1‰之间)。结合华南区域大地构造演化特征、江南造山带主要金矿床成矿地质条件,认为440～400Ma、160～110Ma和～70Ma是该区的三个主要金矿化期;含矿流体主要来源于深部,与变质水和/或岩浆水有关,但成矿晚期有大量再循环的大气降水和/或海水加入。江南造山带湖南段金矿床具有与造山作用有关的浅成型金矿的某些成矿特点。