Rift‐related multistage evolution of the Mangalwar Complex, Aravalli Craton (NW India): Evidence from elemental and Sr–Nd isotopic features of Proterozoic amphibolites. Issue 8 (14th May 2022)

• Record Type: Journal Article
• Authors: Hamidullah, Ismail S.; Mondal, Md. Erfan Ali; Ahmad, Iftikhar; Dash, Jitendra K.; Rahaman, Waliur
• Is Part Of: Geological journal. Volume 57:Issue 8(2022)
• Page Start: 3199
• Page End: 3229
• Publication Date: 2022-05-14
• Subjects: amphibolites -- Aravalli Craton -- Banded Gneissic Complex -- basin opening -- continental rift -- Mangalwar Complex -- Sr–Nd isotope ratios; Geology -- Periodicals; 551
• DOI: 10.1002/gj.4470
• Languages: English
• ISSNs: 0072-1050

Abstract

Abstract : The Banded Gneissic Complex (BGC) of the Aravalli Craton (India) comprises Archean BGC‐I (3.3–2.5 Ga) and Proterozoic BGC‐II. The BGC‐II is a mosaic of amphibolite facies namely, (a) Mangalwar Gneissic Complex (MGC), (b) Mangalwar Metasedimentary Complex (MMC), and (c) granulite‐facies Sandmata Metamorphic Complex. Here we present field, petrography and geochemical study of the Proterozoic amphibolites from the MGC and MMC. Based on field and geochemical data, the amphibolites have been characterized into three types related to rift settings (G1, G2 and G3). The G1 type occurs as dykes in the MGC and bears ocean island basalt‐type rare earth element (REE) patterns along with negative Nb and Ti anomalies, negative to positive values of εNd ( t ) (−0.02 to +3.96) and slightly variable initial 87 Sr/ 86 Sr ( I Sr ) ratios. They are derived from deep mantle sources and correspond to the pre‐rift magmatic phase. The G2 type occurs as isolated patches associated with chert and is characterized by light REE (LREE) depleted and almost flat heavy REE (HREE) patterns suggesting that they were emplaced in an oceanic setting and were derived from a shallower mantle bearing positive εNd ( t ) (+2.87 to +6.27) and I Sr = 0.7002–0.7083. This phase corresponds to the opening of the Mangalwar sedimentary basin (MMC). The G3 type occurs intercalated with metasedimentary rocks of the MMC and marked by LREE‐enriched and HREE‐depleted to flat patterns that resemble Upper Continental Crust signature, their εNd ( t ) mostly negative values and variable I Sr also corroborate this explanation. They are believed to be derived from heterogeneous sources and represent syn‐sedimentary volcanic phases. All these signatures indicate that the amphibolites distinctly represent three phases of magmatism that occurred during pre‐rift (1.72 Ga), opening of basin (1.62 Ga) and syn‐sedimentary volcanism (1.6–1.3 Ga) in the rift‐basin and they were formed during the Proterozoic. These rifting events might have been connected with the fragmentation of Columbia. Abstract : The geotectonic model of the Aravalli Craton (NW India) illustrates the multistage tectono‐magmatic origin of the Mangalwar Complex. The multistage origin of the complex comprises the formation of the Mangalwar basin during the period Paleoproterozoic to Neoproterozoic (1.72–0.95 Ga) followed by emplacement and evolution of different amphibolite types (G1, G2 and G3) in a rift setting.