The continental crust in the overriding plate of the India-Asia collision zone in southern Tibet is characterized by an overthickened layer of felsic composition with an underlying granulite-eclogite layer. A large data set indicates that this crust experienced magmatism from 245 to 10 Ma, as recorded by the Gangdese Batholith. Magmatism was punctuated by flare-ups at 185−170, 90−75, and 55−45 Ma caused by a combination of external and internal factors. The growth of this crust starts with a period dominated by fractional crystallization and the formation of voluminous (ultra)mafic arc cumulates in the lower crust during subduction, followed by their melting during late-subduction and collision, due to changes in convergence rate. This combined accumulation-melting process resulted in the vertical stratification and density sorting of the Gangdese crust. Comparisons with other similarly thickened collision zones suggests that this is a general process that leads to the stabilization of continental crust. ▪The Gangdese Batholith records the time-integrated development of the world's thickest crust, reaching greater than 50 km at 55–45 Ma and greater than 70 km after 32 Ma.▪The Gangdese Batholith records three magmatic flare-ups in response to distinct drivers; the last one at 55−45 Ma marks the arrival of India.▪Magmatism was first dominated by fractional crystallization (accumulation) followed by crustal melting: the accumulation-melting process.▪Accumulation-melting in other collision zones provides a general process for vertical stratification and stabilization of continental crust.

中文翻译：

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藏南 Gangdese Batholith 记录的大陆地壳生长过程


藏南印亚碰撞带上覆板块的大陆地壳的特点是长英质成分层过厚，下层为花岗岩-榴辉岩层。一个大型数据集表明，这个地壳经历了 245 到 10 马 的岩浆作用，正如 Gangdese Batholith 所记录的那样。岩浆作用被外部和内部因素共同引起的 185-170、90-75 和 55-45 马 的爆发所打断。该地壳的生长始于一个以分数结晶为主的时期，在俯冲过程中在下部地壳中形成大量（超）镁铁弧，随后由于收敛速率的变化，它们在晚期俯冲和碰撞期间熔化。这种结合的积累-熔融过程导致了 Gangdese 地壳的垂直分层和密度分选。与其他类似增厚的碰撞带的比较表明，这是导致大陆地壳稳定的一般过程。▪Gangdese Batholith 记录了世界上最厚的地壳的时间综合发展，在 55-45 马 时达到超过 50 公里，在 32 马 之后超过 70 公里.▪Gangdese Batholith 记录了响应不同驱动因素的三次岩浆爆发;最后一次在55-45 马标志着印度的到来.▪岩浆作用首先以分数结晶（积累）为主，然后是地壳融化：积累-熔化过程.▪其他碰撞区的积累-熔化为大陆地壳的垂直分层和稳定提供了一般过程。