The northwestern domains of India record Proterozoic orogenies that reflect global cycles of convergence and extension. A garnet-biotite migmatitic orthogneiss hosted within the Agucha-Kekri Shear Zone sandwiched between the Bhilwara Belt and the North Delhi Fold Belt (NDFB) has two zircon populations yielding U-Pb ages of 1726 and 938 Ma. The older age is correlated with the intrusion of the migmatite protolith, consistent with the partial melting event recorded in gneisses in the southern margin of the Bhilwara Belt. The younger age is interpreted as the age of partial melting and migmatization. Petrographical observations and pressure-temperature (PT) pseudosection analyses indicate incongruent melting of biotite and plagioclase in the gneiss-produced garnet, potash feldspar, and melt under water-fluxed conditions. The peak conditions of ~9 kbar and ≥700°C estimated for the partial melting are similar to those of coeval migmatization recorded at the northwestern margin of the Bhilwara Belt, but lower than those in the adjacent NDFB. This is interpreted to indicate formation of a migmatitic front along the northwestern margin of the Bhilwara Belt while this was being underthrust under the NDFB. Migmatization under similar PT conditions and, at the same time, estimated for the Central Indian Tectonic Zone implies the presence of several loci of crustal amalgamation leading to the final architecture of peninsular India during Rodinia formation.

中文翻译：

---

940 Ma Anatexis in 1726 Bhilwara 带北缘的 Ma Orthogneiss 对印度西北部前寒武纪演化的意义

印度西北部地区记录了反映全球汇聚和扩张周期的元古代造山运动。位于 Bhilwara 带和北德里褶皱带 (NDFB) 之间的 Agucha-Kekri 剪切带内的石榴石-黑云母混合正片麻岩具有两个锆石群，其 U-Pb 年龄分别为 1726 和 938 Ma。年龄较大与混合岩原岩的侵入有关，这与 Bhilwara 带南缘片麻岩中记录的部分熔融事件一致。较年轻的年龄被解释为部分融化和迁移的年龄。岩相学观察和压力-温度 (PT) 假截面分析表明，片麻岩生产的石榴石、钾长石和熔体在水通量条件下的黑云母和斜长石熔融不一致。部分熔融估计的~9 kbar 和≥700°C 的峰值条件与在 Bhilwara 带西北边缘记录的同期混合岩化相似，但低于相邻 NDFB 中的峰值条件。这被解释为表明在 NDFB 下沿 Bhilwara 带的西北边缘形成了混合岩锋。在类似的 PT 条件下，同时估计中印度构造带的混杂作用意味着存在几个地壳合并位点，导致在 Rodinia 形成期间印度半岛的最终结构。这被解释为表明在 NDFB 下沿 Bhilwara 带的西北边缘形成了混合岩锋。在类似的 PT 条件下，同时估计中印度构造带的混杂作用意味着存在几个地壳合并位点，导致在 Rodinia 形成期间印度半岛的最终结构。这被解释为表明在 NDFB 下沿 Bhilwara 带的西北边缘形成了混合岩锋。在类似的 PT 条件下，同时估计中印度构造带的混杂作用意味着存在几个地壳合并位点，导致在 Rodinia 形成期间印度半岛的最终结构。