斜黝帘石中定向金红石的拓扑结构和成因机制  

Topotaxial Relationships and Origin of Orientated Rutile Inclusions in Clinozoisite

作　　者：宋岳庭 徐一凡 赵珊茸[1] 徐畅[1] Song Yueting;Xu Yifan;Zhao Shanrong;Xu Chang(School of Earth Sciences,China University of Geosciences,Wuhan 430074,China)

机构地区：[1]中国地质大学地球科学学院,湖北武汉430074

出　　处：《地球科学》2023年第11期3965-3977,共13页Earth Science

基　　金：国家自然科学基金项目(Nos.41872037,41802042).

摘　　要：大别山红安地区的斜黝帘石榴闪岩中的斜黝帘石普遍含大量定向的针状、棒状的金红石.斜黝帘石(Ca_(2)Al_(2.57)Si_(0.46)[Si_(3)O_(11)]O(OH))是在岩石的退变质过程中形成的,观察到的其内部多组针状金红石的延长方向与主晶形态之间没有固定关系.电子背散射衍射(EBSD)分析表明客晶金红石与主晶斜黝帘石之间具有复杂的结晶学取向关系(CORs),其中<001>_(Rt)//<010>_(Czo)、<100>_(Rt)//<001>_(Czo)、<110>_(Rt)//<001>_(Czo)和<101>_(Rt)//<001>_(Czo)出现几率分别为17.7%,14.9%,14.2%和25.0%.这些取向平行关系对应的轴方向上具有良好的晶格匹配程度.上述每种取向关系对应的金红石针/棒会围绕着这个良好的晶格匹配方向在主晶中旋转360°分布.这种独特的形态分布方式使得我们难以从单个或几个主晶颗粒中直观判断包裹体的形态分布,而使用较大的数据量进行结晶学取向分析对于包裹体的形态分布定性描述是必要的.主客晶之间的拓扑结构和化学分布排除了金红石的出溶成因.Clinozoisite in garnet amphibolite from Hong’an area of Dabie Mountain contains a large amount of oriented needle-like and rod-like rutile inclusions.Clinozoisite(Ca_(2)Al_(2.57)Si_(0.46)[Si_(3)O_(11)]O(OH))is formed during the eclogite retrograde process,and the observed spacial relationships between inclusion and host are not fixed.Electron backscatter diffraction(EBSD)analysis demonstrates complex crystallographic orientations relationships(CORs)between rutile inclusions and host clinozoisite.Among them,CORs<001>_(Rt)//<010>_(Czo),<100>_(Rt)//<001>_(Czo),<110>_(Rt)//<001>_(Czo),<101>_(Rt)//<001>_(Czo)occurred frequently,with occurrence probability of 17.7%,14.9%,14.2%and 25.0%,respectively.The parallel axis of each COR is in high lattice coherency.The rutile needles/rods are distributed and rotated around the directions of high lattice coherency in clinozoisite.The unique morphological distribution makes it difficult to visualize inclusion distribution inside a single or a few host minerals,and crystallographic orientation relationships analysis using a larger database is necessary for the qualitative description of the morphology distribution of inclusions.The exsolution origin is excluded based on the chemical distribution and topotaxial relationships between clinozoisite and rutile.

关 键 词：结晶学取向关系 榴闪岩 斜黝帘石 金红石 包裹体 EBSD 矿物学 结晶学 

分 类 号：P57[天文地球—矿物学]