The Ghansura Rhyolite Dome of the Bathani volcano-sedimentary sequence in eastern India originated from a subvolcanic felsic magma chamber that was intruded by volatile-rich basaltic magma during its evolution leading to the formation of a porphyritic andesite. The porphyritic andesite consists of rapakivi feldspars, which are characterized by phenocrysts of alkali feldspar mantled by plagioclase rims. Results presented in this work suggest that intimate mixing of the mafic and felsic magmas produced a homogeneous hybrid magma of intermediate composition. The mixing of the hot volatile-rich mafic magma with the relatively colder felsic magma halted undercooling in the subvolcanic felsic system and produced a hybrid magma rich in volatiles. Under such conditions, selective crystals in the hybrid magma underwent textural coarsening or Ostwald ripening. Rapid crystallization of anhydrous phases, like feldspars, increased the melt water content in the hybrid magma. Eventually, volatile saturation in the hybrid magma was reached that led to the sudden release of volatiles. The sudden release of volatiles or devolatilization event led to resorption of alkali feldspar phenocrysts and stabilizing plagioclase, some of which precipitated around the resorbed phenocrysts to produce rapakivi feldspars.

印度东部巴塔尼火山-沉积层序的甘苏拉流纹岩圆顶起源于亚火山长英质岩浆房，在其演化过程中被富含挥发分的玄武质岩浆侵入，形成斑状安山岩。斑状安山岩由 rapakivi 长石组成，其特征是由斜长石边缘覆盖的碱性长石斑晶。这项工作中提出的结果表明，基性岩浆和长英质岩浆的紧密混合产生了中间成分的均匀混合岩浆。热的富含挥发物的基性岩浆与相对较冷的长英质岩浆的混合停止了亚火山长英质系统中的过冷，并产生了富含挥发物的混合岩浆。在这样的条件下，混合岩浆中的选择性晶体经历了纹理粗化或奥斯特瓦尔德熟化。无水相（如长石）的快速结晶增加了混合岩浆中的熔融水含量。最终，混合岩浆中的挥发分达到饱和，导致挥发分突然释放。挥发物的突然释放或脱挥发分事件导致碱性长石斑晶的再吸收和稳定的斜长石，其中一些在再吸收的斑晶周围沉淀以产生rapakivi长石。