...
  • 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Journal of Asian earth sciences >Age, petrogenesis and significance of 1 Ga granitoids and related rocks from the Sendra area, Aravalli Craton, NW India
【24h】

Age, petrogenesis and significance of 1 Ga granitoids and related rocks from the Sendra area, Aravalli Craton, NW India

机译：印度西北部Aravalli Craton Sendra地区1 Ga花岗岩和相关岩石的年龄，成因及其意义

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

We present new geochronological, petrological, geochemical and isotopic data for granitic and related rocks from the Aravalli Craton, Rajasthan, northwestern India. In the Sendra area, five variably deformed granitoid plutons, ranging in composition from tonalite to granite, cut across carbonate-rich metasedimentary rocks of the Delhi Supergroup. The largest of these bodies, the Chang pluton (～15 km~2) is dominated by monzogranitic gneisses and aplitic dykes, composed of subequal proportions of quartz, plagioclase (An_(7-20)) and microcline (Or_(92-98)), with lesser biotite (Fe~* = 0.8-0.9) and accessory muscovite (Fe~* = 0.7-0.8). U-Pb zircon data (TIMS method) for a biotite granite gneiss yield a weighted mean ~(207)Pb/~(206)Pb age of 967.8 +- 1.2 Ma, which we interpret as representing the time of magmatic crystallization. Rb - Sr whole-rock isotopic data for the Chang pluton, including new analyses as well as previously published ones, yield a regression of 906 +- 67 Ma (MSWD = 82), which is barely within error of the U-Pb age. There is evidence for open-system behaviour in the Rb-Sr system, particularly for whole-rock samples with low Sr concentrations, and consequently high Rb/Sr. Sm-Nd isotopic data fail to yield meaningful age information. Initial isotopic ratios (at 968 Ma) for Chang pluton granitoids (I_(Sr) = 0.7110 +- 14; ε_(Nd) = -3.28 +- 0.47) are compatible with source materials similar to Archaean amphibolitic rocks of the Banded Gneiss Complex. Spatially associated with the Chang pluton is a massive metagabbro, composed of plagioclase (An_(45-68)) and magnesio-hornblende (Fe~* = 0.3-0.4), with secondary Cl-rich scapolite and ferrian zoisite. The scapolite and zoisite likely crystallized from metamorphic fluids that interacted with nearby calc-silicate schists and gneisses of the Delhi Supergroup. Aside from slight enrichments in Rb, U, Th and Ba, this metagabbro retains a primitive chemical signature similar to N-MORB (LREEdepletion, low K),andinitialisotopicratios(I_(Sr) = 0.7058; ε_(Nd) = +2.9)thatapproachmodeldepletedmantleat968 Ma. The metagabbro is chemically and isotopically similar to mafic metavolcanic and related rocks that have been considered to represent ocean-floor and island-arc basaltic magmas. All available data are compatible with the idea that these rocks represent the products of convergent margin processes during the Early Neoproterozoic, a conclusion that could have important implications for the construction of the Rodinia supercontinent.
机译：我们提供了来自印度西北部拉贾斯坦邦Aravalli Craton的花岗岩和相关岩石的新的年代学，岩石学，地球化学和同位素数据。在森德拉地区，有五种不同变形的花岗岩类岩体，其成分从方钠石到花岗岩，横穿了德里超群富含碳酸盐岩的准沉积岩。其中最大的largest长岩体（〜15 km〜2）主要由单级片麻片和片状脉构成，由等比例的石英，斜长石（An_（7-20））和微斜线（Or_（92-98）组成），黑云母（Fe〜* = 0.8-0.9）和副白云母（Fe〜* = 0.7-0.8）。黑云母花岗岩片麻岩的U-Pb锆石数据（TIMS方法）的加权平均〜（207）Pb /〜（206）Pb年龄为967.8±1.2 Ma，我们将其解释为代表岩浆结晶的时间。 p长岩体的Rb-Sr全岩石同位素数据，包括新的分析和先前发表的分析，得出906 +-67 Ma（MSWD = 82）的回归，这几乎不在U-Pb年龄的误差之内。有证据表明在Rb-Sr系统中存在开放系统行为，特别是对于低Sr浓度，因此Rb / Sr高的全岩样。 Sm-Nd同位素数据无法产生有意义的年龄信息。昌岩体花岗岩的初始同位素比（968 Ma）（I_（Sr）= 0.7110 +-14;ε_（Nd）= -3.28 +-0.47）与类似于带状片麻岩复合体的古生代两性岩石兼容。在空间上与Chang岩浆体相关的是一个大型的变质岩，由斜长石（An_（45-68））和镁镁角闪石（Fe〜* = 0.3-0.4）组成，具有次生的富含Cl的闪锌矿和ferrian zoisite。凹凸石和方沸石可能从与德里超群附近的钙硅酸盐片岩和片麻岩相互作用的变质流体中结晶出来。除了Rb，U，Th和Ba的少量富集外，该金属异物还保留了类似于N-MORB的原始化学特征（LREE耗竭，低K），初始同位素比（I_（Sr）= 0.7058；ε_（Nd）= +2.9），该模型接近耗尽嘛。变质岩在化学和同位素上类似于铁镁质火山岩和相关岩石，这些岩石被认为代表了海底和岛弧玄武岩浆。所有可用的数据都与这些岩石代表新元古代早期收敛边缘过程的产物的观点相符，这一结论可能对罗迪尼亚超大陆的构造具有重要意义。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号