Understanding the Neoproterozoic geodynamics of NW India: clues from tectonomagmatic studies of the Cryogenian Sindreth Basin at the eastern Malani Igneous Province

印度西北部的Sindreth盆地可以看作是双峰火山-深部熔体多相脉冲的档案，代表了持续约20 Ma的马拉尼岩浆活动的一个特征。印度西北部新元古代马拉尼火成岩套（MIS）与邻近巴基斯坦东南部Nagarparkar地区的类似岩浆岩可划分为硅质大火成岩省（SLIP）。该岩浆事件包括主要的长英质火山作用、花岗岩侵位、长英质和基性岩脉侵入。长英质岩石具有典型的a型亲和，主要来源于地壳输入的高温熔融。在项目第一阶段，对双峰套的基性火山岩和岩脉进行了评价，认为其地球化学均质性和衍生自枯竭的大陆地幔源，没有明显的地壳污染。在第二个项目阶段，我们将研究基性岩石的地球化学和放射性成因同位素组成，以确定(1)它们与长英质MIS岩石的关系，(2)岩脉的地幔来源，(3)不同构造块体的地壳岩石的可能污染，以及(4)可能类似于6500万年前德干洪水玄武岩的次大陆岩石圈地幔融化的潜在起源。因此，地球化学研究将深入了解MIS大量岩浆的起源，以及马尔瓦尔和阿拉瓦利克拉通交界处岩石圈的结构和组成。

The Sindreth basin in NW India can be regarded as archive for the multiphase pulses of bimodal volcano-plutonic melts representing a characteristic feature of the c. 20 Ma lasting Malani magmatic activity. The Neoproterozoic Malani Igneous Suite (MIS) in NW India along with analogous magmatic rocks from the adjoining Nagarparkar region in SE Pakistan can be classified as a Silicic Large Igneous Province (SLIP). This magmatic event includes predominant felsic volcanism, granite emplacement and felsic and mafic dyke intrusions. Felsic rocks have typical A-type affinity originated from high temperature melting with major crustal input. It has been evaluated during the first project phase that mafic volcanics and dykes of the bimodal suite show geochemical homogeneity and derivation from a depleted continental mantle source without significant crustal contamination. In this second project phase we will study the geochemical and radiogenic isotope composition of the mafic rocks in order to determine (1) their relation to the felsic MIS rocks, (2) the mantle source(s) of the dykes, (3) the possible contamination with crustal rocks of different tectonic blocks, and (4) the potential origin from melting of subcontinental lithospheric mantle that could be similar to the 65-million-year-old Deccan flood basalts. The geochemical study will thus provide insight into the origin of the large volumes of magmas of the MIS and on the structure and composition of the lithosphere at the boundary between the Marwar and Aravalli Cratons.