Gold mineralization assisted by crustal melting: the case of the Maevatanana mesothermal gold deposit, Madagascar
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ORIGINAL PAPER
Gold mineralization assisted by crustal melting: the case of the Maevatanana mesothermal gold deposit, Madagascar Xi-An Yang 1 & Emmanuel John M. Carranza 2,3 & Jie Wu 4 & Yuchuan Chen 5 & Shanbao Liu 5 & Jiajun Liu 6 Received: 4 July 2018 / Accepted: 9 May 2019 / Published online: 23 May 2019 # Saudi Society for Geosciences 2019
Abstract The genesis of mesothermal Au-quartz vein deposits, which are among the more economically important type of Au deposits, is still under debate. There are two main theories, proposed in the literature, for the subsequent formation of these deposits in suitable structure involved: (1) Au-bearing ore fluid was derived from magmatic intrusions; or (2) Au was extracted from a greenstone belt by metamorphic fluids. In this paper, we report geochemical data from the mesothermal Maevatanana Au deposit in Madagascar, from which we deduce, based on synthesis of these data with field observations and with data from previous studies, that Au-quartz veins and silicified gneisses in the footwall of the granite dike were derived from both greenstone rocks and magmatic intrusions. From this interpretation, we propose a two-stage fertilization model for the mesothermal Maevatanana Au deposit. The first stage involved recycling of metal-fertilized lower crust. The second stage involved emplacement of granitic magma into the greenstone belt, resulting in increase in temperature of the host rock, and subsequent low-degree partial melting of the crust produced volatile-rich high-silica melts. Subsequently, Au-rich fluid was extracted from the granitic magma and convection in the magma reservoir caused by ascent of the less-dense volatile-rich high-silica melt and settlement of crystals (e.g., plagioclase) resulted in the formation of ore-forming fluids at the top of the magma reservoir. Finally, the Au-rich fluids were carried by magmatic dikes and transported from the magma reservoir to shallow host structures to form the mesothermal Maevatanana Au deposit. Keywords Crustal melting . Mineralization . Gold deposit . Madagascar . Greenstone belt
Introduction Editorial handling: M. Barbieri * Xi-An Yang [email protected] * Jiajun Liu [email protected] 1
State Key Laboratory of Nuclear Resources and Environment, East China University of Technology, Nanchang 330013, China
2
Geological Sciences, School of Agriculture, Earth and Environmental Sciences, University of KwaZulu-Natal, Westville Campus, Durban, South Africa
3
Economic Geology Research Centre (EGRU), James Cook University, QLD, Townsville, Australia
4
School of Environment, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
5
Institute of Mineral Resources, Chinese Academy of Geological Sciences, 26 Baiwanzhuang Street, Beijing 100037, China
6
State Key Laboratory of Geological Process and Mineral Resources, China University of Geosciences, Beijing 100083, China
Gold (Au) deposits are formed in a range of geological settings and are divided into different types. Each Au deposit type is a r
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