大别-苏鲁高压、超高压变质带榴辉岩和脉体中磷灰石氯含量和流体盐度关系的研究

Study on the relationship between the fluid salinity and chlorine content of apatites in eclogite and veins from HP and UHP metamorphic belt of the Dabie-Sulu

流体的盐度对含羟基变质矿物组合的稳定温压条件和岩石-流体的相互作用有重要影响。流体的盐度可从矿物中氯含量的角度加以研究。磷灰石是一个含氯矿物,作为副矿物广泛分布在各种岩石中,且能在较宽的温压范围内稳定存在。本文选择大别-苏鲁造山带中典型的高压、超高压岩石开展了磷灰石成分的研究,结合前人流体包裹体的研究结果,探讨了榴辉岩相条件下流体盐度和磷灰石中的氯含量之间的关系。榴辉岩和脉体中磷灰石的XClAp/XOHAp比值与已有的流体包裹体盐度呈很好的线性正相关。榴辉岩和脉体中磷灰石的XClAp/XOHAp比值范围为0.00～0.35时,对应的流体包裹体盐度约为0～40%NaCleqv。

Fluid salinity plays an important role on P-T stability fields of hydroxyl-bearing mineral assemblages and metasomatism during fluid-rock interaction. Salinity of fluid may be determined by chlorine （ C1 ） contents of minerals. Apatite, as a ubiquitous mineral in various rocks, is an ideal candidate for the study on the relationship between salinity in fluid and C1 content in apatite due to its simple chemical compositions and broad stable P-T field. This paper focuses on measurement of the compositions of apatites in eclogite-facies veins and host eelogites from HP-UHP metamorphic belt of the Dabie-Sulu eclogite-bearing. Combining with the data of salinity of fluid inclusions from other researchers, we built the relationship between the salinities of fluid inclusions and chlorine content of apatites in eclogite and hosted veins. It shows positively correlated between XCIAp/XoHAp ratios in apatites and the salinities of fluid inclusions from the eclogites and veins. The Xctnp/XonAp ratios in apatite from 0. 00 to 0. 35 are approximately equilibrated with the salinities from 0 to 40% NaCleqv in fluid inclusions.