Metamorphic and Metasomatic Kyanite-Bearing Mineral Assemblages of Thassos Island (Rhodope, Greece)
Metamorphic and Metasomatic Kyanite-Bearing Mineral Assemblages of Thassos Island (Rhodope, Greece)
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萨索斯岛（希腊罗多彼）的变质和交代含蓝晶石矿物组合
作者：
A. Tarantola;P. Voudouris;Aurélien Eglinger;C. Scheffer;Kimberly Trebus;Marie Bitte;Benjamin Rondeau;C. Mavrogonatos;Ian T. Graham;Marius Etienne;C. Peiffert
Trikorfo地区（希腊北方罗多彼岛Thassos岛）是一个独特的矿物学地区，富含锰矿物，包括蓝晶石、红柱石、石榴石和绿帘石。它们鲜艳的颜色和巨大的晶体尺寸使它们成为宝石级材料的良好指标，尽管迄今为止发现的晶体太破碎而不能被视为可销售的宝石。主要岩性为石榴石-蓝晶石-黑云母-赤铁矿-斜长石±十字石±硅线石副片麻岩。热力学Perple_X模型表明了ca. 630-710 °C和7.8-10.4千巴。变质后交代硅酸盐和钙硅酸盐（富锰）矿物发现于（i）绿红色层位，矿物学分带为透辉石、角闪石、绿帘石和钙铝榴石，（ii）云母片岩，含锰铝榴石、蓝晶石、红柱石和硬绿柱石，以及（iii）弱变形石英长石粗粒脉，蓝晶石在与变质片麻岩的界面处。向脆性条件的过渡表现为阿尔卑斯型拉张裂隙，包括伟晶岩-绿帘石-斜绿泥石-角闪石-石英脉，横切变质叶理。蓝晶石特别令人感兴趣，因为它存在于变质共生体中，局部存在于各种颜色的交代组合中（蓝色至绿色/黄色透明和橙子）。元素分析和紫外-近红外光谱分析表明，颜色的变化是由于Ti 4 +-Fe 2+，Fe 3+和Mn 3+与Al 3+的组合替代。结构和矿物学观察表明，Trikorfo地区经历了两个阶段的演变，在中新世高品位主岩的折返过程中，变质后热液循环导致当地从韧性到脆性条件的交代反应。各种各样的矿物成分和组合点的矿物学和fO 2条件在交代反应和热液活性流体与围岩之间的相互作用的局部控制。
The Trikorfo area (Thassos Island, Rhodope massif, Northern Greece) represents a unique mineralogical locality with Mn-rich minerals including kyanite, andalusite, garnet and epidote. Their vivid colors and large crystal size make them good indicators of gem-quality materials, although crystals found up to now are too fractured to be considered as marketable gems. The dominant lithology is represented by a garnet–kyanite–biotite–hematite–plagioclase ± staurolite ± sillimanite paragneiss. Thermodynamic Perple_X modeling indicates conditions of ca. 630–710 °C and 7.8–10.4 kbars. Post-metamorphic metasomatic silicate and calc-silicate (Mn-rich)-minerals are found within (i) green-red horizons with a mineralogical zonation from diopside, hornblende, epidote and grossular, (ii) mica schists containing spessartine, kyanite, andalusite and piemontite, and (iii) weakly deformed quartz-feldspar coarse-grained veins with kyanite at the interface with the metamorphic gneiss. The transition towards brittle conditions is shown by Alpine-type tension gashes, including spessartine–epidote–clinochlore–hornblende-quartz veins, cross-cutting the metamorphic foliation. Kyanite is of particular interest because it is present in the metamorphic paragenesis and locally in metasomatic assemblages with a large variety of colors (zoned blue to green/yellow-transparent and orange). Element analyses and UV-near infrared spectroscopy analyses indicate that the variation in color is due to a combination of Ti4+–Fe2+, Fe3+ and Mn3+ substitutions with Al3+. Structural and mineralogical observations point to a two-stage evolution of the Trikorfo area, where post-metamorphic hydrothermal fluid circulation lead locally to metasomatic reactions from ductile to brittle conditions during Miocene exhumation of the high-grade host-rocks. The large variety of mineral compositions and assemblages points to a local control of the mineralogy and fO2 conditions during metasomatic reactions and interactions between hydrothermal active fluids with surrounding rocks.