Sri Lankan gem Deposits- occurrence and geology（斯里兰卡宝石矿床-产状与地质）

报告题目：Sri Lankan gem Deposits- occurrence and geology（斯里兰卡宝石矿床-产状与地质）

报告人：Sanjeewa P.K. Malaviarachchi（院士/教授）

单位：University of Peradeniya，Sri Lanka（斯里兰卡佩拉德尼亚大学）

报告时间：2023年12月12日（周二下午）15：00-16：30

报告地点：明辨楼C205

报告人简介：

Dr. Sanjeewa Maalviarachchi，Academician of the Sri Lankan Academy of Sciences, completed his PhD from the Institute of Planetary Materials at Misasa, Okayama University, Japan majoring in mantle petrology, geochemistry and radiogenic isotope geology. He holds MSc from Shimane University, Japan in metamorphic petrology and BSc (Honours) from University of Peradeniya, Sri Lanka. His research interests are igneous and metamorphic petrology, hard rock geochemistry, and isotope geology. He is a professor at the Department of Geology, University of Peradeniya. Currently, he serves as a Visiting Scholar at the Institute of Geology and Geophysics, Chinese Academy of Sciences, Bejing, China.

Sanjeewa Maalviarachi教授于2023年获得斯里兰卡科学院院士称号。其在日本冈山大学行星材料研究所取得博士学位，期间的研究方向为地幔岩石学、地球化学和放射成因同位素地质学。在此之前，他在日本岛根大学变质岩石学理学硕士学位，在斯里兰卡佩拉德尼亚大学获得理学学士学位。他的研究方向包括火成岩和变质岩岩石学、岩石地球化学和同位素地质学。他是斯里兰卡佩拉德尼亚大学地质系教授，现为中国科学院地质与地球物理研究所访问学者。

报告内容简介：

Sri Lanka is well known for its wide variety of gem minerals for over 2500 years. Gem discoveries in India, Madagascar, Tanzania, Mozambique etc share common geological origin with respect to the high-grade metamorphism at continental collision zone in the Gondwana, highlighting occurrences of good quality corundum, spinel, topaz, zircon, aquamarine, amethyst, gem varieties of quartz, tourmaline, chrysoberyl, zircon, beryl, garnet, sphene, topaz etc. Geologists have found similar gem minerals in eastern Antarctica, confirming the presence of a Pan-African mineral belt (originated at about 550 million years ago) from east Africa through India-Sri Lanka to Antarctica. The similarity of the geological features of these gem-bearing lithologies has been attracted internationally by both geologists and gemmologists.

Nearly all the gem formations are located in the central high-grade metamorphic terrain of the Highland Complex geological unit in Sri Lanka. The gem deposits are classified as sedimentary, metamorphic, and magmatic; the sedimentary types being the most abundant. Nearly all the gem deposits of Sri Lanka are derived from the granulite facies metamorphic rocks of the Highland Complex, clearly indicating that there were high-temperature petrological conditions (>600 °C) suitable for the formation of gemstones. Overall, the source rocks of the gem minerals are skarns, marbles, pegmatites, garnetiferous and charnockitic gneisses.

2500多年来，斯里兰卡以其丰富多样的宝石矿物而闻名。斯里兰卡与印度、马达加斯加、坦桑尼亚和莫桑比克等地的宝石矿床一样，其成因都跟冈瓦纳大陆碰撞带的高级变质作用有着密切的关系，这些地区均分布有优质刚玉、尖晶石、黄玉、锆石、海蓝宝石、紫水晶、石英、电气石、金绿宝石、锆石、绿柱石、石榴石、榍石、黄玉等宝石品种。地质学家在东南极洲发现了类似的宝石矿物，证实了从东非经印度-斯里兰卡到南极洲的泛非宝石成矿带（起源于约5.5亿年前）的存在。这些含宝石岩性地质特征的相似性在国际上受到地质学家和宝石学家的广泛关注。

斯里兰卡的宝石地层几乎都位于其中部高地杂岩地体中。宝石矿床分为沉积型、变质型和岩浆型；沉积类型最为丰富。斯里兰卡几乎所有的宝石矿床都来源于高地杂岩的麻粒岩相变质岩，这表明该地质单元存在适合宝石形成的高温高压条件（>600°C）。总体而言，宝石矿物的源岩为矽卡岩、大理岩、伟晶岩、含石榴石以及紫苏花岗质片麻岩。

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