英云闪长岩奥长花岗岩花岗闪长岩(TTG)岩石构造组合及其亚类划分

TTG岩石构造组合(或岩类)表征洋壳俯冲作用。本文提出TTG岩类的4个亚类：(1)镁安山岩系列(MA)低压型TTG亚类，形成于非常年轻和很热的洋壳俯冲，压力≤1 500~1 600 MPa，深度≤50~60 km，例如活动洋中脊俯冲的板片窗的边缘；(2)镁安山岩系列(MA)高压型TTG亚类，形成于比较年轻和较热的洋壳俯冲，压力≥1 500~1 600 MPa，深度≥50~60 km；(3)低镁(或非镁)安山岩系列(LMA)低压型TTG亚类，形成于洋内弧下地壳，压力≤1 500~1 600 MPa，深度≤50~60 km；(4)低镁(或非镁)安山岩系列(LMA)高压型TTG亚类，形成了大陆边缘弧山根带，压力≥1 500~1 600 MPa，深度≥50~60 km。对TTG岩类4个亚类的研究，并结合对无TTG形成的老的冷的俯冲带洋壳和冷的弧地壳以及幔楔有无岩浆产生等方面的研究，可以重建岩浆弧的壳幔结构和热结构，进而可为与洋俯冲有关的成矿作用提供地质背景。

Discussion on the tonalite-trondhjemite-granodiorite (TTG) petrotectonic assemblage and its subtypes.

The TTG petrotectonic assemblage (or igneous series) characterizes subduction of oceanic crust. In this paper, we suggest four subtypes of the TTG series: (1) The magnesium andesite (MA) lower pressure subtype is formed at a subduction zone of very young oceanic crust at highest temperature, ≤15001600 MPa pressure and ≤5060 km depth, for example, at the margins of the slab-window of the active mid-oceanic ridge subduction. (2) The magnesium andesite (MA) higher pressure subtype is formed at a subduction zone of relatively young oceanic crust at high temperature, ≥15001600 MPa pressure and ≥5060 km depth. (3) The lower (or non) magnesium andesite (LMA) lower pressure subtype is formed at a lower crust of the intra-oceanic island arc at ≤15001600 MPa pressure and ≤5060 km depth. And (4) The lower (or non) magnesium andesite (LMA) higher pressure subtype is formed at the mountain root of the continental arc at ≥15001600 MPa pressure and ≥5060 km depth. Using a combination of the four TTG assemblage subtypes and non-magma generation at the subduction zone of older oceanic crust at low temperature with or without magma generation at the mantle wedge, we may reconstruct the crust-mantle and thermal structures of the magmatic arcs and provide a geologic basis for oceanic subduction related mineralization.