Mineral Transformations in Low Grade Rocks

以扫描电镜和扫描透射电镜（SEM/STEM）技术为重点，研究了细粒泥质岩从早期成岩作用到低变质作用的演化过程。从代表各种过程范围的样品序列中提取矿物的质地、成分和结构，每一种都被表征，以便区分表征过程的变化。具体项目包括：(a)蒙脱石向伊利石转变的表征。(b)伊利石的组成、缺陷状态和晶体尺寸的演变，部分是为了确定伊利石“结晶度”变化的起源。(c)绿泥石变化的演变导致绿泥石结晶度的变化。(d) MORB的渐进式热液蚀变，重点是三八面体层状硅酸盐混合层关系的演化。(e)泥岩中三八面体混合层状硅酸盐的递进演化。(f) Na/K二八面体云母的演化。(g)泥质接触变质作用。(h)形成具有绿泥石/云母“堆”的均质页岩。(i) XRD图谱与混层粘土序列的关系。这项研究解决了细粒沉积物如何成为变质岩的基本问题。

The evolution of fine-grained pelitic rocks from early diagenesis through low grade metamorphism is being studied with an emphasis on techniques of scanning and scanning transmission electron microscopy (SEM/STEM). The textures, compositions and structures of minerals from sequences of samples representing the ranges of a variety of processes are each being characterized in order to distinguish the changes that characterize the processes. Specific projects include: (a) characterization of the smectite to illite transformation. (b) evolution of the composition, defect- state and crystal dimensions of illite, in part to determine the origins of changes in illite "crystallinity." (c) evolution of changes in chlorite leading to changes in chlorite crystallinity. (d) prograde hydrothermal alteration of MORB with emphasis on the evolution of mixed-layer relations of trioctahedral phyllosilicates. (e) prograde evolution of trioctahedral mixed- layer phyllosilicates in pelites. (f) evolution of Na/K dioctahedral micas. (g) contact metamorphism of pelites. (h) formation of homogenized shales with chlorite/mica "stacks." (i) relation between XRD patterns and mixed-layer clay sequences. The research addresses the fundamental question as to how fine-grained sediments become metamorphic rocks.