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首页> 外文期刊>Journal of Asian earth sciences >Petrology, geochemistry and magnetic properties of Sadara sill: Evidence of rift related magmatism from Kutch basin, northwest India
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Petrology, geochemistry and magnetic properties of Sadara sill: Evidence of rift related magmatism from Kutch basin, northwest India

机译：萨达拉基岩的岩石学，地球化学和磁学性质：来自印度西北部库奇盆地的裂谷相关岩浆作用的证据

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摘要

Mafic volcanic rocks of the Mesozoic Kutch basin represent the earliest phase of Deccan volcanic activity. An olivine-clinopyroxene-plagioclase-phyric undersaturated basalt occurs as a sill near Sadara in the Pachham upland, Northern Kutch. The Sadara sill is deformed and emplaced along faults. The sill is alkaline in character and is transitional between basalt and basanite. Compared to primitive mantle, the Sadara sill is enriched in Sr, Ba, Pb and LREE but depleted in Nb, Cr, Y, Cs and Lu. Fractional crystallization of olivine and clinopyroxene from an alkaline mafic melt generated by low degree partial melting of mantle peridotite can explain the observed chemical variation in the sill. IRM and L-F test experiments and mineral analyses show titano-magnetite as the major remanence carrying magnetic mineral. AF and thermal demagnetizations of the Sadara sill yielded a mean ChRM direction as D = 315.6°, I = -43.0° (α_(95) = 9.78; k = 25.38) and the corresponding VGP at 25°S; 114.6°E (dp/dm=6.58°/11.6°). The Sadara sill pole is significantly different from those of the Deccan (65 Ma) and the Rajmahal Traps (118 Ma) but is close to the Cretaceous poles of 85-91 Ma rock units from southern India. This suggests a pre-Deccan age for the sill.
机译：中生代库奇盆地的镁铁质火山岩是德肯火山活动的最早阶段。在北库奇北部帕查姆山地的萨达拉（Sadara）附近，石橄榄石-斜辉石-斜长石-岩浆-饱和玄武岩出现。萨达拉岩台沿断层变形并被定位。窗台是碱性的，在玄武岩和玄武岩之间过渡。与原始地幔相比，萨达拉基岩富含Sr，Ba，Pb和LREE，但富含Nb，Cr，Y，Cs和Lu。由地幔橄榄岩的低度部分熔融所产生的碱性镁铁质熔体的橄榄石和斜辉石的部分结晶可以解释观察到的基石化学变化。 IRM和L-F测试实验以及矿物分析表明，钛磁铁矿是携带磁性矿物的主要剩磁。 Sadara窗台的AF和热消磁产生的平均ChRM方向为D = 315.6°，I = -43.0°（α_（95）= 9.78; k = 25.38）和相应的VGP在25°S;东经114.6°（dp / dm = 6.58°/ 11.6°）。 Sadara基台极与Deccan（65 Ma）和Rajmahal Traps（118 Ma）的极不同，但靠近印度南部85-91 Ma岩石单元的白垩纪极。这表明门槛的预装年龄。

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