【摘要】 大量的岩石学证据表明：碰撞造山带中常发育900～1100℃的超高温变质作用。然而，碰撞造山带中如何出现如此极端的超高温条件仍然存在争议。为了更好地理解超高温变质作用加热机制和碰撞造山带中主要热源的相对贡献，我们建立了一系列高分辨率二维热-动力学模型，借此探讨了俯冲大陆岩石圈密度亏损程度、大陆地壳放射性生热率和大陆汇聚速率等因素对碰撞造山过程中超高温变质主要热源的影响。当大陆岩石圈密度亏损(Δρ=ρ_{软流圈地幔}-ρ_{岩石圈地幔})大于50kg/m³时，有利于发生大陆平板俯冲，软流圈地幔无法上涌为地壳物质提供热源；此时，具有较高放射性生热率（>3μW/m³）的地壳可以发生“浅俯冲-折返”型超高温变质作用。而当大陆岩石圈密度亏损小于10kg/m³时，大陆上地壳在深俯冲阶段首先发生超高压榴辉岩相变质作用，随后伴随着大陆岩石圈地幔后撤和软流圈上涌，进而出现以异常高的地幔热流加热为主的“深俯冲-折返”型超高温变质作用。此外，较低的大陆汇聚速率（<1cm/yr）更有利于“深俯冲-折返”型超高温变质作用的产生。将数值模拟结果与特提斯构造域的变质岩石数据和地球物理观测进行对比，我们认为在现今板块构造体制下，由具有密度亏损程度较高的大陆岩石圈平俯冲有利于“浅俯冲-折返”型超高温变质作用的发生，而由密度亏损程度较低的大陆岩石圈俯冲可能导致“深俯冲-折返”型超高温变质作用的产生。更多还原

【Abstract】 Many lines of petrological evidence show that ultra-high temperature（UHT） metamorphism of 900～1100℃ often developed in collisional orogens. However, how such extreme ultra-high temperature conditions arose in collision orogens is still a matter of debate. In order to better understand the heating mechanism of UHT metamorphism and the relative contribution of the main heat sources in collision orogens, we have established a series of high-resolution 2-D numerical models to investigate the influence of several key factors such as the degree of density depletion of the continental lithosphere, the radioactive heat production（RHP） of the continental upper crust and the rate of continental convergence on the main heat sources of ultrahigh temperature metamorphism. When the density depletion of a continental lithosphere(Δρ=ρ_{asthenosphere}-ρ_lithosphere) is greater than 50kg/m³, the flat subduction of the continental lithosphere is generally resulting, and the asthenosphere mantle cannot upwell to provide heat source for the continental crust. With a higher RHP（>3μW/m³）, the continental upper crust can undergo “shallow subduction-exhumation” type UHT metamorphism. However, when the density depletion of the continental lithosphere is less than 10kg/m³, the continental upper crust undergoes ultra-high pressure eclogite facies metamorphism during the deep subduction stage, followed by mantle retreat and asthenosphere upwelling, and then “deep subduction-exhumation” type ultra-high temperature metamorphism dominated by abnormally high mantle heat flow heating. In addition, the lower continental convergence rate（<1cm/yr） is more favorable to the generation of “deep subduction-exhumation” type UHT metamorphism. By comparing the numerical modelling results with the metamorphic rock data and geophysical observations in the Tethyan tectonic domain, we conclude that, under the present plate tectonic system, the flat subduction of the continental lithosphere with higher density depletion is favorable to the occurrence of “shallow subduction-exhumation” type UHT metamorphism; while the subduction of a continental lithosphere with lower density depletion may lead to “deep subduction-exhumation” type UHT metamorphism.更多还原