苏鲁超高压变质带南部浅变质岩的全岩Rb-Sr同位素年龄

提供了苏鲁超高压变质带南部震旦纪浅变质千枚岩的全岩Rb Sr同位素年龄测试数据 ,获得了 2 2 1± 14Ma的等时线年龄。对测试结果的分析认为 :该年龄为浅变质岩的变质年龄。区域调查对比表明 ,低绿片岩相变质作用在造山带组成岩石中普遍存在 ,并叠加于超高压变质岩石 ,因而上述年龄代表在印支期存在普遍的退变质作用年龄。浅变质岩中印支期同位素年龄的获得 ,对正确认识超高压变质带的演化具有重要意义。     

Isotopic evidence of middle proterozoic magmatism from bombay high field: Implications to crustal evolution of western offshore of India

Precambrian granitic basement rocks obtained from well BH-36 of Bombay High Field, western offshore of India has been studied both by Rb-Sr and K-Ar dating methods. Seven basement samples chosen from two cores have yielded whole rock Rb-Sr isochron age of 1446 ± 67 Ma with an initial⁸⁷Sr/⁸⁶Sr ratio of 0.7062 ± 0.0012. This age has been interpreted as the formation/emplacement time of the granite. Two biotite fractions of different grain size separated from a sample CC6B2T have yielded Rb-Sr mineral isochron age of 1385 ± 21 Ma. However, these fractions when studied by K-Ar dating method have yielded slightly higher but mutually consistent ages of 1458 ± 43 Ma and 1465 ± 43 Ma, respectively. Further, two biotites separated from additional samples CC5B9T and CC6B3B have yielded K-Ar ages of 1452 ± 42 Ma and 1425 ± 40 Ma with an overall mean age of 1438 ± 19 Ma. This mean K-Ar age is indistinguishable from whole rock Rb-Sr isochron as well as mineral isochron age within experimental error. The similarity in the whole rock and biotite ages obtained by different isotopic methods suggests that no thermal disturbance has occurred in these rocks after their emplacement/formation around 1450 Ma ago. The present study provides the evidence for the existence of an important Middle Proterozoic magmatic event around 1400-1450 Ma on the western offshore of India which, hitherto, was thought to be mainly confined to the eastern Ghats, Satpura and Delhi fold belt of India. This finding may have an important bearing on the reconstruction of Proterozoic crustal evolution of western Indian shield.     

新疆哈密百灵山铁矿地质特征及成矿时代

文章总结了前人对百灵山铁矿的研究成果,并对已发表的地质图件进行了修正。首次对矿石中含矿石英脉中的流体包裹体进行了Rb_Sr等时线年龄测定,结果为(293±10)Ma,确定了该矿床的成矿时代为石炭纪末—二叠纪初。     

山西中条山地区北峪奥长花岗岩的同位素年龄和同位素地球化学特征

追索北峪奥长花岗岩与围岩（早元古代绛县群变富钾流纹岩）接触关系，发现北峪奥长花岗岩已侵入于围岩地层中，表明其为早元古代岩浆型侵人体。使用全岩Ｒｂ－Ｓｒ等时线方法测定北峪奥长花岗岩时代，获得的年龄为２１０７±５９Ｍａ（２），由此推断北峪岩体成岩时代为２１００Ｍａ，代表了本区绛县运动岩浆深成事件年龄。其８７Ｓｒ／８６Ｓｒ初始比值为０．７０２３，呈现出幄源花岗岩的特点，但结合其铝过饱和特点以及具高的Ｏ全岩比例，推测其主要来源于下地壳麻粒岩相变质的沉积岩，但可能存在地幔物质添加或已遭受地幔交代作用的改造。     

川西丹巴地区变质岩的Rb—Sr年代学研究

丹巴地区自中生代以来经历了多期的变形、变质和岩浆作用。根据变质程度差异划分出6个变质带：矽线石带、蓝晶石带、十字石带、石榴子石带、黒云母带和绢云母－绿泥石带。蓝晶石带十字石片岩和石榴石带斜长角闪岩与变玄武岩的矿物Rb－Sr等时线年龄分别为149.0±7.1Ma，160.0±13.0Ma和150.2±2.4Ma，它们代表该区最主要的一次区域动热变质事件年龄。本文还结合已有的年代学资料，讨论了丹巴地区变质作用演化史     

中国滇西南造山带变质岩的Sm-Nd和Rb-Sr同位素年代学

滇西南造山带的主体由多期变质的岩石单元组成。变质和变形年代的确定是研究它们构造演化的关键之一。哀牢山群和大勐龙群斜长角闪岩分别得到1367Ma和1436Ma的Sm-Nb等时线年龄,这代表了高级角闪岩相的变质时代。它们的形成年龄约为2000～1600Ma。崇山群黑云斜长片麻岩获得了与此相当的1900～1600Ma的Sm-Nd模式年龄。澜沧群的蓝片岩的Sm-Nd等时线年龄为1287Ma,绿片岩的Sm-Nd模式年龄为1300～1200Ma。上述各组岩石还获得了约为1000Ma、500～400Ma、300～180Ma和180～140Ma的几组Rb-Sr等时线或Sm-Nd和Rb-Sr模式年龄,分别代表了后期重要构造事件。     

Rb-Sr age of the Sivamalai alkaline complex,Tamil Nadu

The Sivamalai alkaline complex comprises ferro-, pyroxene-hornblende- and nepheline-syenites. Field relations show that the nepheline syenites followed the emplacement of non-feldspathoidal syenites. Mineralogical data on the syenite suite have been reviewed. The Sivamalai alkaline rocks are not strongly enriched in rare-earth elements like most miaskites. Rb-Sr isotopic analyses of a suite of six samples from the various members of the complex define an isochron corresponding to an age of 623 ±21 Ma (2σ) and initial Sr ratio of 0.70376 ±14 (2σ). This is consistent with a model of fractional crystallization of a parent magma derived from an upper mantle source with apparently no isotopic evidence for more than one magma source for the complex. The Sivamalai alkaline complex represents a Pan-African alkaline magmatic event in the southern granulite terrane of Peninsular India.     

阴山东段先寒武变质岩的Rb-Sr年代

采自阴山东段先寒武变质岩的全岩样品给出四个等时线年龄。下部集宁群为2497±124Ma;上部乌拉山群为2367±127Ma;上部二道洼群给出两个年龄:2067±39Ma和325±16Ma。据此认为,2.5Ga前发生了麻粒岩化;2.35Ga前发生混合岩化;2.0Ga和0.33Ga前有变质事件叠加。     

Genesis of the Maka Pb-Zn-W deposit in southeastern Yunnan" Constraints from sphalerite Rb-Sr dating,cassiterite U-Pb dating and in -situ S,Pb isotopes of sulfideSCIEI北大核心CSCD

马卡铅锌钨矿床地处云南省马关县与麻栗坡县的南温河交界处,位于燕山晚期老君山复式花岗岩体北缘。野外地质调查发现,该矿床主要发育矽卡岩型、石英脉型铅锌矿化和萤石石英脉型白钨矿化,但它们的形成机制仍缺乏系统研究。本文通过闪锌矿Rb-Sr、锡石原位U-Pb同位素定年和硫化物原位S、Pb同位素分析,厘定了马卡矿床不同类型铅锌矿化年龄,并探讨了其成矿物质来源及成因机制。矽卡岩型和石英脉型铅锌矿石中闪锌矿分别获得了88.9±1.9Ma(MSWD=4.5)和85.18±0.72Ma(MSWD=1.2)的Rb-Sr等时线年龄,同时获得石英脉型铅锌矿石中锡石LA-ICP-MS U-Pb年龄为84.3±4.7Ma(MSWD=0.66)。结果指示锌、锡矿化时代为晚白垩世,矽卡岩型和石英脉型铅锌矿化分别与该区广泛出露的老君山花岗岩(-90Ma)和花岗斑岩年龄(80-86Ma)一致。矿石硫化物原位硫同位素测试结果显示,δ34S值范围为2.53‰-9.65‰,均值为4.7‰,与老君山花岗岩中硫化物硫同位素组成(4.07‰)相似,表明硫主要来源于老君山花岗岩,少部分源自沉积地层;原位铅同位素组成特征也表明矿石铅主要源自老君山花岗岩。综合研究认为,老君山花岗岩体南北缘地区具有相似的成矿地质条件。马卡矿床的形成主要与燕山晚期老君山复式花岗岩体有关,可能经历了与花岗岩有关的矽卡岩型矿化和与花岗斑岩有关的热液充填、交代成矿过程。