Abstract The plumbing architecture of the Neoproterozoic Malani Igneous Suite (MIS), representing one of the largest, intraplate, anorogenic rhyolitic volcanism in western Rajasthan, is poorly constrained. We present a crustal scale model from gravity anomaly modelling also supported by other geological and geophysical observations. The regional-residual separation using frequency filtering technique reveals the presence of high-density discreet bodies at different crustal levels. A 2½D forward and 3D constrained inversion of the residual gravity anomaly suggests the presence of sediments covering MIS, and 6–8 km thick high-density sills emplaced in upper crust down to ~9 km depth. The high gravity anomalies in the remaining part of the Bouguer anomaly could be explained by the presence of 10–12 km thick high-density magmatic intrusion at the base of the Moho below 32–38 km depth. These high-density bodies may be attributed to mafic/ultramafic cumulates during MIS magmatism. It appears that the magmatic melts migrated upwards from the mantle to lower crustal magma reservoirs may alter the bulk magma composition by crustal assimilation. The ensuing density contrast would lead to the upward migration of the dominant felsic melt and their emplacement at shallower depths.

中文翻译：

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印度西部新元古代马拉尼火成岩套组下的残余羽头

摘要 新元古代马拉尼火成岩组 (MIS) 的管道结构是拉贾斯坦邦西部最大的、板内、无造山流纹岩火山之一，受到的约束很差。我们提出了一个重力异常建模的地壳比例模型，也得到了其他地质和地球物理观测的支持。使用频率滤波技术的区域残差分离揭示了在不同地壳水平上存在高密度离散体。残余重力异常的 2.5D 正向和 3D 约束反演表明存在覆盖 MIS 的沉积物，以及位于上地壳中至约 9 公里深度的 6-8 公里厚的高密度基岩。布格异常其余部分的高重力异常可以用莫霍面底部 32-38 公里深度以下 10-12 公里厚的高密度岩浆侵入来解释。这些高密度体可能归因于 MIS 岩浆作用期间的镁铁质/超镁铁质堆积。似乎岩浆熔体从地幔向上迁移到下地壳岩浆储层可能会通过地壳同化作用改变大量岩浆成分。随之而来的密度对比将导致主要的长英质熔体向上迁移并在较浅的深度就位。似乎岩浆熔体从地幔向上迁移到下地壳岩浆储层可能会通过地壳同化作用改变大量岩浆成分。随之而来的密度对比将导致主要的长英质熔体向上迁移并在较浅的深度就位。似乎岩浆熔体从地幔向上迁移到下地壳岩浆储层可能会通过地壳同化作用改变大量岩浆成分。随之而来的密度对比将导致主要的长英质熔体向上迁移并在较浅的深度就位。