层状侵入体及其韵律层成因

LAYERED INTRUSIONS AND ITS ORIGION OF RHYTHMIC LAYERING

层状侵入体以其独特的韵律结构记录了岩浆的演化分异过程。围绕韵律层理的成因 ,不同学者提出了很多成层机制 ,归纳起来大体有两类 :一类与岩浆流动和动力成层有关 ,包括流动分异、对流成层、化学成因等 ;另一类为非动力成层机制 ,主要有火成堆积、重力分异、压实作用和固化收缩等观点。影响韵律形成的因素很多 ,通常包括岩浆成分、对流作用、扩散作用、热梯度、氧逸度、温度和压力等。在评述这些成层机制和影响因素的基础上 ,结合攀枝花层状侵入体的特点 ,认为该岩体的韵律结构是在岩浆的固化收缩和压实作用下 ,晶体定向生长和自组织排列的结果 ,是二元 (辉石 ,斜长石 )、固 (岩石 )—液 (岩浆 )相转变系统中动量、能量和物种质量的复杂耦合所形成的分形自组织现象。对层状侵入体的进一步研究应集中在加强实验 (尤其是高温高压实验 )、引入非线性分析以及与成矿研究相结合等方面。

Research on layered intrusion with rhythmic structure has great significance in geological and geophysical field. A wide variety of layer forming mechanisms have been proposed focused on two respects: One is magmatic flow and dynamic layering, such as flow segregation, convection layering, crystal growth and so on; the other is non dynamic layering, including gravity settling, solidification contraction, compaction, etc. Many studies indicate there are some factors controlling the formation of the rhythms. These factors include magma composition, convection, diffusion, thermal gradient, oxygen fugacity, temperature, pressure, the shape of magma chamber etc. Based on these mechanisms and the characteristic of Panzhihua intrusion, this kind of rhythmic layer was formed under the solidification contraction and compaction of the magma. At the same time, the crystals underwent self origination and grew along the preferred orientation. Further studies on layered intrusions should be focused on a) strengthening experiment at high temperature and high pressure, b) nonlinear analysis and c) combining with ore forming mechanisms.