赣东北前寒武纪岩浆混合作用岩带的发现及其地质意义  

DISCOVERY FOR PRECAMBRIAN MAGMATIC MIXED ZONE FROM NORTHEASTERN JIANGXI PROVINCE AND THEIR GEOLOGICAL SIGNIFICANCE

作　　者：李昌年[1] 

机构地区：[1]中国地质大学地球科学学院,武汉430074

出　　处：《地学前缘》1999年第4期331-337,共7页Earth Science Frontiers

基　　金：原国家计划委员会和原地质矿产部专项基金

摘　　要：在总结新近发现的赣北前寒武纪岩浆混合岩带地质特征的基础上，从地质学、岩相学和同位素地球化学的角度，论证了发生于这一特殊地质时期和地质背景下的岩浆混合作用。文中将该作用形成的岩浆混合杂岩体有效地分解为：（１） 偏酸性端员的岩浆岩（ 角闪石英正长岩、石英正长岩） ；（２） 基性端员岩浆岩（ 玄武玢岩、玄武安山玢岩） 和（３） 岩浆混合岩，后者又可分为非均一岩浆混合岩和均一岩浆混合岩（ 如石英二长闪长岩） 。阐明该岩浆混合作用是新元古期我国东南地区江南古洋向扬子古陆俯冲消减这一构造演化的重要物质表现；示踪该地区于中元古期（１４８ ～１８５ Ｇａ） 经历了一次与全球范围一致的壳 幔分离事件和新元古期（０８５ Ｇａ） 亏损地幔与大洋沉积物在源区混合的事件；确认该地区前寒武纪的岩浆混合作用和岩浆侵入作用实际上是一个连续的岩浆作用序列。This thesis is based on the geological character summarization of the Precambrian magmatic mixed zone which was lately discovered in northeastern Jiangxi Province. According to the geology, the petrography and the isotopic geochemistry, it is proved that the magmatic mixing occurred in a special geological time and setting. The author effectively divided it into magma mixed complex bodies formed by magmatic mingling: ① the meta acidic end member magmatic rocks (hornblende quartz syenite, quartz syenite), ② the basic end member magmatic rocks (basalt porphyry, andesite basalt porphyry), and ③ the magma mixed rocks, the latter was subdivided again into heterogeneous and homogeneous magma mixed rocks (e.g. quartz monzodiorite). The thesis explained that the magmatic mixing was an important event of tectonic evolution, which was resulted from subduction of Jiangnan old ocean into Yangtze old continent in southeastern China in Upper Proterozoic subera. It revealed that there was an event of the segregation between crust and mantle in Middle Proterozoic subera (1.48～1.85 Ga), and there was one of mutual mixing between depleted mantle and the oceanic sedimentary in Upper Proterozoic subera (0.85 Ga), the former had taken place in the whole world. It is determined that the Precambrian mixing and intrusion are a continuous ordered series in this province, but both were constrained by compression of approximately S-N under the common stress field.

关 键 词：赣东北 前寒武纪 岩浆混合 杂岩体 岩带 

分 类 号：P588.36[天文地球—岩石学] P588.11[天文地球—地质学]