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首页> 外文期刊>Journal of Asian earth sciences >Perovskite U-Pb age and petrogenesis of the P-12 kimberlite from the Eastern Dharwar craton, southern India: Implications for a possible linkage to the 1110 Ma large igneous province
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Perovskite U-Pb age and petrogenesis of the P-12 kimberlite from the Eastern Dharwar craton, southern India: Implications for a possible linkage to the 1110 Ma large igneous province

机译：来自印度南部Dharwar Craton东部Dharwar Craton的P-12金伯里术的钙钛矿年龄和培养性：对可能的联系到1110 MA大火省的可能性

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摘要

Petrology, bulk-rock geochemistry, and perovskite U-Pb age for the P-12 kimberlite pipe from the Wajrakarur kimberlite field, Eastern Dharwar craton (EDC) of southern India is reported. Pemvskites yielded a high-precision U-Pb age of 1122 +/- 7.7 Ma, taken to be an emplacement age of the host P-12 kimberlite pipe. The groundmass of coherent facies P-12 kimberlite contains monticellite, clinopyroxene, andradite, atoll spinel with titanomagnetite trend, and pemvskite with an elevated REE contents. Phlogopite shows restricted Al2O3 and TiO2 contents. Furthermore, olivines with a wider and higher range of core compositions (i.e. Mg# = 84-94) and multi-granular nodules are the hallmark features of the P-12 pipe. This assorted primary mineral content and its composition indicates the transitional nature of the P-12 towards the Kaapvaal lamproites. However, concentrations of bulkrock major and trace elements in the P-12 and other Wajrakarur kimberlites are similar to the global hypabyssal magmatic kimberlites. Large ion lithophile and high field strength elements (e.g. Ba and Nb) and their ratios (e.g. La/Nb and Th/Nb) suggest the presence of a heterogeneous and lithosphere influenced mantle source region which have been severely overprinted by metasomatizing fluids/melts emanating from the deep sourced upwelling mantle. The presence of such mixed and metasomatized mantle source regions likely to be an important factor for the transitional nature of the P-12 and other Mesopmterozoic kimberlites.Based on the availability of the newest emplacement ages, we propose a geodynamic model for the origin of kimberlites in the Indian subcontinent. The U-Pb age of 1122 +/- 7.7 Ma for the P-12 pipe shows its close temporal association to the emplacement of the recently proposed 1110 Ma Large Igneous Province (LIP), with plume center beneath the NW part of the Kalahari craton. Emplacement of the P-12 and other contemporaneous Indian kimberlites, therefore, marks the impingement of mantle plume which contributed heat and triggered partial melting of metasomatized lithospheric mantle without melt input. The eruption phase of similar to 100 million years (i.e. 1050-1153 Ma), for the kimberlites and related rocks in the Indian shield, does not appear to be continuous and can be separated into several short-durational magmatic events. For this reason, small-volume, volatile-rich magmatism during the Mesoproterozoic time in India is linked to the presence of a number of LIPs and associated mantle plumes during Columbia to Rodinia supercontinent transition and assembly of cratonic blocks of the latter.
机译：据报道，来自Wajrakarur Kimberlite领域的P-12金伯利斯特田，印度南部的Dharwar Craton（EDC）的P-12金伯利岩植物岩石学，岩石地球化学和Perovskite U-PB年龄。 Pemvskites产生了1122 +/- 7.7 mA的高精度U-PB Age，是宿主P-12金伯里条管的施加年龄。相干面P-12金伯利铝酸盐的粉末含有Monticellite，Clinopogogne，Andradite，环状旋光丝带，具有升高的REE含量的Pemvskite。 Phogopite显示限制Al 2 O 3和TiO2内容物。此外，具有较宽且较高范围的核心组合物（即Mg＃= 84-94）和多粒状结节的橄榄石是P-12管的标志特征。这种什锦的初级矿物质含量及其组合物表明p-12向Kaapvaal Lamproites的过渡性质。然而，P-12和其他Wajrakarur Kimberlites中的Bulkrock主要和微量元素的浓度类似于全球催眠岩浆金霉素。大离子亲和高场强元素（例如Ba和Nb）和它们的比率（例如LA /铌和Th / Nb）的建议的非均相和岩石圈的存在的影响已通过metasomatizing流体/熔体发出了严重套印地幔源极区从深水升起的搭便车。这种混合和弥物的裂缝源区的存在可能是P-12和其他脑外杂交金伯利玻璃的过渡性质的重要因素。基于最新的施加年龄的可用性，我们提出了一种基因粘土起源的地球动力学模型在印度次大陆。 P-12管道的U-PB年龄为1122岁+/- 7.7 mA表现出其密切的时间关联与最近提出的1110 MA大火省（嘴唇）的施加，在Kalahari Craton的NW部分下面有羽毛中心。因此，P-12和其他同期印度金伯莱粘物的施加标志着披风羽流的撞击，这促进了不含熔融输入的弥扑型岩石罩的热量和触发的部分熔化。对于印度盾牌的金伯利特和相关岩石，爆发阶段类似于1亿年（即1050-1153 mA），这似乎并不连续，并且可以分成几个短期岩浆事件。出于这个原因，在印度中奥斯普罗佐越时的小批量挥发性的岩浆主义与在哥伦比亚到罗迪尼亚的罗马尼亚超大过渡和后者的克拉氏块组装的罗马尼亚的许多嘴唇和相关的地幔羽毛的存在有关。

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