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

印度西北部的辛德雷思盆地可视为双峰火山-深成熔体多期脉冲的档案，代表了约20 Ma持续马拉尼岩浆活动的特征。印度西北部新元古代马拉尼火成岩与巴基斯坦东南部Nagarparkar地区类似的岩浆岩可归类为硅质大火成岩省(SLIP)。这一岩浆事件包括主要的长英质火山作用、花岗岩侵位和长英质和镁铁质岩墙侵入。长英质岩石具有典型的A型亲和力，起源于主要地壳输入的高温熔融。在项目第一阶段进行的评估表明，双峰岩套的镁铁质火山岩和岩墙显示出地球化学均一性，来自贫化的大陆地幔来源，没有明显的地壳污染。在这个二期工程中，我们将研究镁铁质岩石的地球化学和放射性同位素组成，以确定(1)它们与长英质MIS岩的关系，(2)岩墙的地幔来源(S)，(3)可能与不同构造块体的地壳岩石混染，(4)类似于6500万年前德干溢流玄武岩的次大陆岩石圈地幔熔融的潜在来源。因此，这项地球化学研究将有助于洞察马瓦尔克拉通和阿拉瓦利克拉通交界处大量岩浆的来源以及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.