Understanding the petrogenetic evolution of Archean gabbroic cumulates provides a window to the mantle geodynamics operated in the early Earth. Gabbroic cumulates are associated with various tectonic settings including convergent plate boundaries, mantle plumes, mid-ocean ridges, anorogenic, post-orogenic, continental rift settings and oceanic plateaus. The exposures of preserved gabbroic suites in the Archean are limited. The Mesoarchean Mayurbhanj Gabbro Anorthosite Complex (GAC) is a well-preserved mafic body situated along the eastern margin of the craton along with concomitant anorogenic Mayurbhanj granite. These rocks are devoid of deformational structures and/or mineral recrystallization. Based on their mineralogical characteristics, GAC rocks are mainly grouped into gabbronorite, leucogabbronorite, leucogabbro and gabbro. The minimal abundance of magmatic amphibole and the variation in the anorthite content (An₃₆-An₈₄) rules out the role of a hydrous mantle source in the evolution of these rocks. The studied samples display tholeiitic trend transitioning to calc-alkaline field, major and trace element data indicates the fractional crystallization of olivine and pyroxene. The trace element systematics of the Mayurbhanj GAC show LILE enrichment over HFSE depletion, with negative Nb-Ta and mixed Zr-Hf and Ti anomalies. The geochemical signatures such as elevated Th/Yb, Nb/Yb, variable Dy/Yb and Dy/Dy* and varying Gd/Yb_CN ratios suggest that parental magmas of the Mayurbhanj GAC originated from a heterogeneous depleted mantle source. The studied rocks' Sr-Nd isotopic systematics reveal that their parental magma has undergone assimilation by a Paleoarchean felsic crust. We argue that the ‘arc-like’ geochemical signatures displayed by these rocks resulted from crustal contamination and may not be due to subduction origin. Consolidating the field, geochemical and isotopic evidence suggests that the Mesoarchean Mayurbhanj GAC possibly evolved from an anhydrous heterogeneous mantle source in a non-compressive tectonic regime.

了解太古代辉长岩堆积物的成岩演化为了解早期地球的地幔地球动力学提供了一个窗口。辉长岩堆积与各种构造环境有关，包括会聚板块边界、地幔柱、大洋中脊、造山带、造山后、大陆裂谷环境和大洋高原。在太古代保存的辉长岩套房的曝光是有限的。中太古宙 Mayurbhanj Gabbro Anorthosite Complex (GAC) 是一个保存完好的基性体，位于克拉通东部边缘，伴随着无造山的 Mayurbhanj 花岗岩。这些岩石没有变形结构和/或矿物再结晶。根据其矿物学特征，GAC岩石主要分为辉长岩、白辉长岩、白辉长岩和辉长岩。₃₆ -An ₈₄ ) 排除了含水地幔源在这些岩石的演化中的作用。所研究的样品显示拉斑向钙碱性场转变的趋势，主要和微量元素数据表明橄榄石和辉石的分级结晶。Mayurbhanj GAC 的微量元素系统学显示 LILE 富集超过 HFSE 消耗，具有负 Nb-Ta 和混合 Zr-Hf 和 Ti 异常。地球化学特征，例如升高的 Th/Yb、Nb/Yb、可变的 Dy/Yb 和 Dy/Dy* 以及变化的 Gd/Yb _CN比率表明 Mayurbhanj GAC 的母岩浆起源于异质枯竭地幔源。所研究的岩石的 Sr-Nd 同位素系统学表明它们的母岩浆经历了古太古代长英质地壳的同化作用。我们认为这些岩石显示的“弧状”地球化学特征是地壳污染造成的，可能不是俯冲起源。综合该领域、地球化学和同位素证据表明，中太古代 Mayurbhanj GAC 可能从非压缩构造体系中的无水异质地幔源演化而来。