中生代冈底斯弧的岩浆成因与地壳演化

活动陆缘弧的岩浆成因和密度分选过程是理解大陆地壳形成机制和演化过程的关键。本项目针对亚洲大陆南部中生代冈底斯弧的特殊性（大量角闪石岩、玄武安山质的地壳平均成分），聚焦岩浆成分较为连续的两个时间断面（约200 Ma、约90 Ma）的岩浆记录。在冈底斯弧东部开展7条南北向岩浆岩剖面调研和相关岩石学、矿物学、年代学和地球化学测试。通过与北美Cordilleran大陆边缘弧岩浆成因和地壳演化的对比，分析冈底斯弧特有的大量堆晶角闪石岩的成因和未出现石榴子石辉石岩的原因，初步构建冈底斯弧两个时间断面的垂向地壳成分剖面，最终回答“为何中生代冈底斯活动大陆边缘弧发育大量角闪石岩、地壳平均成分为玄武安山质？”这一科学问题。本项目成果不但有助于揭示中生代冈底斯弧的岩浆成因和壳幔过程，而且还可为研究新生代时期冈底斯弧巨厚地壳的形成演化提供关键的初始条件，创新和提高对活动陆缘弧的岩浆成因和大陆地壳形成机制的认识。

Petrogenesis and density filtering of arcs in active continental margins are central to understanding the formation and evolution of continental crust. This project sheds lights on the magmatic records of two compositionally successive sections at 200 ± 5 Ma and 90 ± 5 Ma due to the occurrence of a large amount of hornblendites and the presence of an arc crust with basaltic andesitic composition in average. This project collects new field, petrological, mineralogical, geochronological, and geochemical data from seven north-south sampling traverses across the eastern Gangdese arc to compare with the extensively studied North American Cordilleran arc in terms of petrogenesis and crustal evolution. We aim to explore the origin of abundant hornblendites and the causes of lacking garnet pyroxenites that are unique in the Gangdese arc and to construct two vertical crustal compositional sections at 200 ± 5 Ma and 90 ± 5 Ma, ultimately making response to the scientific question of “Why are there a large amount of hornblendites and a basaltic andesitic composition in averaged crust of the Mesozoic Gangdese active continental margin arc?” The results of this project are not only favored to explain the petrogenesis and crustal-mantle interaction of the Mesozoic Gangdese arc, but also provide initial conditions for understanding the formation of over-thickened Gangdese crust in the Cenozoic. These results are expected to innovate and improve our knowledge on the petrogenesis of continental arc magmatism and mechanism for continental crustal formation in active continental margins.