Abstract Accretionary orogens are hallmarks of subduction tectonics along convergent plate margins. Here we report a sequence of low-grade metasediments carrying exhumed blocks of ultramafic, mafic and felsic rocks from Sargur in the Western Dharwar Craton in India. These rocks occur along the southern domain of the Chitradurga Suture Zone, which marks the boundary between the Western and Central Dharwar Cratons and thus provide a window to explore Archean convergent margin processes. We present zircon U-Pb and Lu-Hf data from Sargur metasediments including quartz mica schist, fine-grained quartzite, and pelitic schist, as well as from blocks/layers of trondhjemite, garnet amphibolite, and chromite-bearing serpentinite occurring within the metasedimentary accretionary belt. The detrital zircon grains from the metasediments show multiple age groups, with the oldest age as 3482 Ma and an age peak at 2862 Ma. Magmatic zircons in trondhjemite show 207Pb/206Pb weighted mean age of ca. 2972 Ma, whereas those in the chromite-bearing serpentinite display multiple age populations of ca. 2896, 2750, 2648, 2566 and 2463 Ma, tracing zircon crystallization in an evolving mantle wedge adjacent to a subducting oceanic plate. Metamorphism is dated as ca. 2444 Ma from zircon grains in the garnet amphibolite. Zircon eHf(t) in the mafic-ultramafic rocks and trondhjemite are mostly positive, suggesting a juvenile (depleted mantle) source. The detrital zircon Lu-Hf data suggest that the sediment source involved Paleoarchean juvenile and reworked components. Based on our findings, we propose that the Sargur sequence represents an accretionary melange which forms part of a major Mesoarchean accretionary orogen that witnessed multiple stages of tectonic erosion at least during three periods at ca. 3200–3000 Ma, 3000–2800 Ma and 2800–2500 Ma removing a large part of the accretionary prism along the convergent margin. We correlate the processes with prolonged subduction-accretion cycle culminating in the final collision between the Western and Central Dharwar cratonic blocks.

中文翻译：

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印度南部太古代达尔瓦尔克拉通中太古代增生混杂和构造侵蚀：早期地球板块构造

摘要 增生造山带是会聚板块边缘俯冲构造的标志。在这里，我们报告了一系列低品位变质沉积物，它们携带着从印度西达尔瓦尔克拉通的萨古尔挖掘出的超镁铁质、镁铁质和长英质岩石块。这些岩石出现在 Chitradurga 缝合带的南部区域，该区域标志着达尔瓦克拉通西部和中部之间的边界，因此提供了一个探索太古代收敛边缘过程的窗口。我们提供了来自 Sargur 变沉积岩的锆石 U-Pb 和 Lu-Hf 数据，包括石英云母片岩、细粒石英岩和泥质片岩，以及在变质沉积岩中出现的长闪长岩、石榴石角闪岩和含铬铁矿蛇纹岩块/层的锆石 U-Pb 和 Lu-Hf 数据增生带。变质沉积物中的碎屑锆石颗粒显示出多个年龄组，年龄最大为 3482 Ma，年龄峰值为 2862 Ma。长闪长岩中的岩浆锆石显示约 207Pb/206Pb 的加权平均年龄。2972 Ma，而含铬蛇纹岩中的那些显示出大约 2972​​ Ma 的多个年龄群。2896、2750、2648、2566 和 2463 Ma，追踪与俯冲大洋板块相邻的演化地幔楔中的锆石结晶。变质作用的日期为大约。2444 Ma 来自石榴石角闪岩中的锆石颗粒。镁铁质-超镁铁质岩石和长闪长岩中的锆石 eHf(t) 大多为正值，表明为幼年（贫化地幔）源。碎屑锆石 Lu-Hf 数据表明沉积物来源涉及古太古代幼体和再加工成分。根据我们的发现，我们认为 Sargur 层序代表了一种增生混杂岩，它构成了一个主要的中太古代增生造山带的一部分，该造山带至少在大约三个时期内见证了多个阶段的构造侵蚀。3200-3000 Ma、3000-2800 Ma 和 2800-2500 Ma 沿会聚边缘去除了大部分增生棱柱。我们将这些过程与延长的俯冲-增生周期相关联，最终导致西达尔瓦克拉通块体和中达尔瓦克拉通块体之间的最终碰撞。