In Late Proterozoic mafic granulites of the Sandmata Complex in Rajasthan, northwestern India, multilayer corona textures were formed along the interface between orthopyroxene and plagioclase. We examined the metamorphic conditions and processes of formation of these coronae, which provide an insight into the interplay between steady state and sequential diffusion-controlled mineral growth mechanisms. The individual corona–symplectite layers consist of clinopyroxene + quartz|garnet + clinopyroxene|garnet + quartz|K-feldspar, from the inner to the outer margins of the coronae. The single-value decomposition models suggest that the multilayered coronae were formed in a locally closed system, via sequential diffusion of Mg, Fe and Ca into the reaction zone, which has acted as the main driving force for the growth of corona textures. The relict orthopyroxene with exsolved clinopyroxene yields primary crystallization conditions of 8.4 ± 1.5 kbar and ~ 1100–1000 °C. Clinopyroxene in the innermost corona layer grew at ~ 9 kbar and 850–800 °C, whereas clinopyroxene + garnet grew outward at ~ 8 kbar and 700–600 °C. Subsequent hydrous retrogression (~ 6 kbar and 600–550 °C) resulted in the development of rimward zoning in garnet and the growth of amphibole. On combining textural relations and the above conventional P–T estimates, a near-isobaric cooling P–T path was reconstructed using phase equilibria modeling. Further, the near-isobaric cooling path is consistent with the magmatic underplating hypothesis in the Sandmata Complex, where the intrusion of magmatic bodies (i.e., Gyangarh–Asind igneous complex and Anjana granite) favored the development of granulite facies assemblage in norite and gabbronorite protoliths.

在印度西北部拉贾斯坦邦Sandmata复合体的晚元古代镁铁质花岗质颗粒中，沿邻二茂铁和斜长石之间的界面形成了多层电晕纹理。我们研究了这些日冕的变质条件和形成过程，从而为稳态和顺序扩散控制的矿物生长机制之间的相互作用提供了见识。从电晕的内部边缘到外部边缘，单个电晕-亚铜矿层由斜辉石+石榴石+斜辉石|石榴石+石英|钾长石组成。单值分解模型表明多层电晕是通过Mg，Fe和Ca依次扩散到反应区中而在局部封闭的系统中形成的，这已成为电晕纹理生长的主要驱动力。残留的邻苯二甲酚和已溶解的斜铁基吡啶产生的主要结晶条件为8.4±1.5 kbar，约1100–1000°C。最内层电晕层中的次氯环己烯在〜9 kbar和850-800°C下生长，而次氯环己烯+石榴石在〜8 kbar和700-600°C处向外生长。随后的含水退缩（〜6 kbar和600–550°C）导致石榴石边缘区域的发展和闪石的生长。关于结合语篇关系和上述传统 随后的含水退缩（〜6 kbar和600–550°C）导致石榴石边缘区域的发展和闪石的生长。关于结合语篇关系和上述传统 随后的含水退缩（〜6 kbar和600–550°C）导致石榴石边缘区域的发展和闪石的生长。关于结合语篇关系和上述传统P–T估计，使用相平衡模型重建了接近等压的冷却P–T路径。此外，近等压冷却路径与Sandmata岩浆中的岩浆下渗假说相一致，其中岩浆体（即，Gyangarh-Asind火成岩复合体和Anjana花岗岩）的侵入有利于在黑土和辉长岩原石中的粒岩相组合的发展。 。