Partial equilibrium textures such as corona provide information on changing pressure–temperature (P-T) conditions experienced by a rock during its geological evolution. Coronae layers may form in single or multiple stages; understanding the genesis of each layer is necessary to correctly extract information regarding the physicochemical conditions experienced by the rock. Mafic rocks from SE Chotanagpur Granite Gneissic Complex, India, show the presence of multi-layered coronae at olivine–plagioclase contact with the mineral sequence: olivine | orthopyroxene | amphibole + spinel | plagioclase. Textural studies indicate that the coronae formed during metamorphism in a single stage due to a reaction between olivine and plagioclase. Reaction modelling shows that the corona formation occurred in an open system and experienced a minor volume loss. Pseudosection modelling and thermobarometry suggest that the P-T conditions related to corona formation are 860 ± 50°C and 7 ± 0.5 kbar. A μMgO-μCaO diagram shows that the layers in coronae formed in response to chemical potential gradients between the reactant minerals. A combination of field observations and the P-T conditions of coronae formation suggest a fluid-driven metamorphism. Correlation with extant geological information indicates that the corona-forming event is possibly related to the accretion of India and Antarctica during the assembly of Rodinia.

中文翻译：

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日冕的起源和早期新元古代热事件的影响：来自印度 SE Chotanagpur 花岗岩片麻岩复合体的案例研究

诸如电晕之类的部分平衡纹理提供了有关压力-温度变化的信息（磷-吨) 岩石在其地质演化过程中所经历的条件。电晕层可以单阶段或多阶段形成；了解每一层的成因对于正确提取有关岩石所经历的物理化学条件的信息是必要的。来自印度 SE Chotanagpur 花岗岩片麻岩杂岩的镁铁质岩石在橄榄石-斜长石与矿物序列的接触处显示出多层日冕的存在：橄榄石 | 斜方辉石| 高分辨率照片| CLIPARTO 闪石+尖晶石| 斜长石。纹理研究表明，由于橄榄石和斜长石之间的反应，在变质过程中形成了一个单一阶段的日冕。反应模型显示，电晕形成发生在开放系统中，并经历了轻微的体积损失。伪截面建模和热气压测量表明，磷-吨与电晕形成相关的条件是 860 ± 50°C 和 7 ± 0.5 kbar。一个μ氧化镁-μ氧化钙图表显示，日冕中的层是响应于反应物矿物之间的化学势梯度而形成的。结合实地观察和磷-吨日冕形成的条件表明流体驱动的变质作用。与现存地质资料的相关性表明，日冕形成事件可能与罗迪尼亚集结期间印度和南极洲的吸积有关。