...
  • 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>South African Journal of Geology: Being the Transaction of the Geological Society of South African: Syndie die Verhandelinge van die Geologiese Vereniging van Suid-Afrika >ANATEXIS OF JUVENILE MAFIC TO INTERMEDIATE CRUST CONSTRAINTS FROM MAJOR AND TRACE ELEMENT AND SR, ND, PB ISOTOPES OF DIORITES TO GRANITES (DAMARA OROGEN, NAMBIA)
【24h】

ANATEXIS OF JUVENILE MAFIC TO INTERMEDIATE CRUST CONSTRAINTS FROM MAJOR AND TRACE ELEMENT AND SR, ND, PB ISOTOPES OF DIORITES TO GRANITES (DAMARA OROGEN, NAMBIA)

机译：幼年黑胶质的中间壳构成的蚁体，主要形态和痕量元素以及SR，ND，PB的同位素从硅酸盐到颗粒状（达玛拉·奥尔根，纳米比亚）

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

The Tsomtsaub pluton (central Damara orogen, Namibia) consists of quartz diorites, granodiorites and granites. Intrusion ages of the undeformed and unmetamorphosed quartz diorites and granites are constrained by LA-ICP-MS U-Pb zircon analyses, which yielded ages of 541 +/- 3 Ma (quartz diorites) and 506 +/- 6 Ma (granodiorites), respectively. The older age predates the main phase of high-T regional metamorphism and the younger age fits to the inferred age of the main peak of regional metamorphism. Elemental and isotope variations are decoupled, indicating that combined assimilation-fractional crystallization processes were not important during evolution of these rocks. Therefore, Sr-Nd isotope compositions (quartz diorites: epsilon Nd-(init)-1.5 to -1.8; Sr-87/Sr-86((init)) 0.7049 to 0.7058; granodiorites/granites: epsilon Nd-(init): -2.7 to -5.3; Sr-87/Sr-86((init)): 0.7044 to 0.7096) indicate that generation of the quartz diorites and granodiorites involved distinct sources. Lead isotope ratios show some overlap between quartz diorites ((206)pb/(204)pb: 18.36 to 18.38; Pb-207/Pb-204: 15.66 to 15.67; Pb-208/Pb-204: 38.09 to 38.12) and granodiorites/granites ((206)pw(204)pb: 18.39 to 18.78; (207)pb/ Pb-204 : 15.62 to 15.67; Pb-208/Pb-204: 37.90 to 38.17). However, a large variation in Pb-207/Pb-204 at relatively constant (206)pb/(204)pb is apparent for all rock types. Based on a comparison with results from fluid-absent melting experiments using amphibolites, a lower crustal metabasalt, probably enriched in 1(20, is a likely source rock for the quartz diorites. For the granodiorites, a high-K andesitic or tonalitic source is likely. The granites are interpreted as fractionation products of the granodiorites. Semi-quantitative pressuretemperature estimates using Qtz-Ab-Or systematics and Zr saturation temperatures indicate pressures in excess of 5 kbar and temperature of c. 900 C, placing the site of melting in the lower crust. The weakly evolved Sr-Nd isotope ratios and the moderate radiogenic Pb isotope ratios are consistent with juvenile mafic to intermediate sources for the quartz diorites and granodiorites. This contrasts with previous suggestions favouring an origin of quartz diorites and granodiorites by either melting of an enriched mantle source during Pan-African times followed by AFC processes, or by melting of ancient, depleted mafic crust.
机译：Tsomtsaub岩体（纳米比亚中部达马拉造山带）由石英闪长岩，花岗闪长岩和花岗岩组成。 LA-ICP-MS U-Pb锆石分析限制了未变形和未变质的石英闪长岩和花岗岩的侵入年龄，产生的年龄为541 +/- 3 Ma（石英闪长岩）和506 +/- 6 Ma（红闪长岩），分别。年龄早于高T区域变质作用的主要阶段，而年龄小则适合于区域变质作用的主要高峰的推断年龄。元素和同位素的变化是解耦的，表明在这些岩石的演化过程中，合并的同化-分馏结晶过程并不重要。因此，Sr-Nd同位素组成（石英亚闪石：epsilon Nd-（init）-1.5至-1.8; Sr-87 / Sr-86（（init））0.7049至0.7058;花岗岩/花岗岩：epsilon Nd-（init）： -2.7至-5.3; Sr-87 / Sr-86（（init））：0.7044至0.7096）表明石英闪长岩和花岗闪长岩的产生涉及不同的来源。铅同位素比显示石英闪长岩（（206）pb /（204）pb：18.36至18.38; Pb-207 / Pb-204：15.66至15.67; Pb-208 / Pb-204：38.09至38.12）和花岗闪长岩之间有一些重叠/花岗岩（（206）pw（204）pb：18.39至18.78;（207）pb / Pb-204：15.62至15.67; Pb-208 / Pb-204：37.90至38.17）。但是，对于所有岩石类型，在相对恒定的（206）pb /（204）pb处，Pb-207 / Pb-204的变化很大。根据与两闪石无流体熔融实验结果的比较，可能会富集1（20）的下部地壳偏玄武岩可能是石英闪长石的烃源岩。对于花岗闪长石，高钾安山岩或tonalitic岩浆是使用Qtz-Ab-Or系统分析仪和Zr饱和温度的半定量压力温度估算值表明压力超过5 kbar，温度约为900°C，从而将花岗岩解释为花岗闪长岩的分馏产物。发育缓慢的Sr-Nd同位素比和适度的放射成因的Pb同位素比与石英黑闪石和花岗闪长岩的幼稚镁铁质到中间来源相一致，这与以前的主张通过熔融或熔融形成石英红闪石和花岗闪长岩的建议形成对比。泛非时期富集的地幔源，接着是AFC流程，或者是古代贫瘠的黑手党小伙子的融化t。

著录项

相似文献

  • 外文文献
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