Fluid-present melting of the deep crust: implications for the tectonics of large convergent orogens

陆壳深部流体与岩石的相互作用对造山带的形成和崩塌过程中物质和能量的重新分配以及矿床的形成起着重要作用。在大型山脉的形成过程中，地壳增厚使地壳深部的温度和压力升高。大量的流体流入山带下方的深部热地壳，促进了部分熔融，从而大大削弱了大片大陆地壳。这些熔融弱化的区域可能充当大规模的剪切带，促进山脉的形成，或者可能横向流向造山带前缘，导致高海拔高原的形成。例如，地球物理成像表明，喜马拉雅山带下方存在大面积的部分熔融地壳，这种熔融弱化物质的横向运动被认为在青藏高原的发展中起着一级作用。虽然广泛的流体流动的部分熔融可能有重要的构造后果，这些流体的来源，成分和运输途径的约束不足。这部分是由于缺乏进入现代山脉带之下的地壳深部的途径。

The interaction of fluids with rocks in the deep continental crust plays a critical role in the redistribution of mass and energy during the buildup and collapse of mountain belts and the genesis of ore deposits. During the construction of large mountain belts, crustal thickening generates elevated temperatures and pressures in the deep crust. Widespread fluid influx into the deep hot crust beneath mountain belts promotes partial melting, which drastically weakens large regions of continental crust. These melt-weakened regions may act as large-scale shear zones that facilitate mountain buildup or may flow laterally towards orogenic fronts resulting in the formation of high-elevation plateaux. For example, geophysical imaging suggests that large regions of partially molten crust are present beneath the Himalayan mountain belt and the lateral movement of this melt-weakened material is proposed to play a first-order role in the development of the Tibetan Plateau. While widespread fluid-fluxed partial melting may have important tectonic consequences, the sources, compositions and transport pathways of these fluids are poorly constrained. This is due, in part, to the lack of access to the deep crust beneath modern mountain belts.