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榍石是变质岩石中很常见的副矿物.在榍石中有多种常见的元素替代关系,A1和Fe~(3+)常取代八面体中的Ti,同时OH和F取代非四面体中的O.这些元素类质同像替代关系可通过公式Ti+O=(Al,Fe~(3+)+(OH,F)来表示.Smith将榍石的端元组分划分为5种:CaTiSiO_4O(氧钛榍石)、CaFe~(3+)SiO_4OH(羟铁榍石)、CaFe~(3+)SiO_4F(氟铁榍石)、CaAlSiO_4OH(羟铝榍石)和CaAlSiO_4F(氟铝榍石).其中,CaTiSiO_4O和Ca(Al,Fe~(3+))SiO_4(OH,F)之间为不连续固溶体.自然界的榍石中CaAlSiO_4(OH,F)端元组分的含量可在0%～50%之间变化.按照矿物晶格中Al含量的不同,榍石被划分为低铝榍石(X_(Al)<0.25)和高铝榍石(X_(Al)>0.25).在高压和超高压大理岩及产于其中的榴辉岩中,高铝榍石常作为一种高压和超高压矿物产出,在这些高压和超高压榍石中Al常替代八面体位置中的Ti,同时F替代非四面体位置中的O.这种耦合替代关系(Al+F=Ti+O)被认为是高压或超高压变质作用在榍石晶格中的反映,是一种具高压或超高压效应的替代关系.最近我们在产于苏鲁超高压变质带东南端的荣城杨官屯的大理岩中发现含P和Mg的高铝榍石.本文简要地描述了这种高铝榍石的产出特征和矿物化学成分,并讨论了其晶格中的元素替代关系及其高压效应.
Mudstone is a common accessory mineral in metamorphic rocks. There are many common elemental substitutions in the rock, A1 and Fe3 + often replace Ti in the octahedron, and OH and F replace the non-tetrahedron Of O. The isomorphism of these elements is represented by the formula Ti + O = (Al, Fe ~ (3 +) + (OH, F) CaTiSiO_4O, CaFe ~ 3+ SiO_4OH, CaFe ~ 3+ SiO_4F, CaAlSiO_4OH and CaAlSiO_4F, ), In which CaTiSiO 4 O and Ca (Al, Fe 3+) SiO 4 (OH, F) are discontinuous solid solutions.The content of CaAlSiO 4 (OH, F) % To 50% .According to the Al content in the crystal lattice, the apatite is divided into the low aluminum (X_ (Al) <0.25) and the high aluminum (X_ (Al)> 0.25) High-pressure and extra-high pressure marble and the eclogites produced in it are frequently produced as high-pressure and ultrahigh-pressure minerals. In these high-pressure and ultrahigh-pressure rocks, Al often replaces Ti in octahedral sites , While F replaces the non-tetrahedral position O. This coupling substitution (Al + F = Ti + O) is considered as high pressure or super High-pressure metamorphism is a reflection of the high-pressure or ultrahigh-pressure effect in the crystalline lattice of the feldspar.Recently we found high P and Mg contents in the marble of Yangguantun, Rongcheng, southeast of the Sulu UHP metamorphic belt This paper briefly described the output characteristics and mineralogical composition of this high-aluminaite, and discussed its elemental substitution and its high pressure effect in its lattice.