Evaluating the diamond potential of kimberlite-hosted diamond deposits from the North China Craton

被引：0
作者：
Ni P. [1 ]
Zhu R. [1 ]
机构：
[1] State Key Laboratory for Mineral Deposit Research, School of Earth Science and Engineering, Nanjing University, Nanjing
来源：
Dizhi Xuebao/Acta Geologica Sinica | 2020年 / 94卷 / 09期
关键词：
Diamond; Diamond dissolution; Diamond potential evaluation; Kimberlite; The North China Craton;
D O I：
10.19762/j.cnki.dizhixuebao.2020244
中图分类号：
学科分类号：
摘要：
The diamond potential evaluation of kimberlite-hosted primary diamond deposit is important for understanding of diamond metallogenic rule and guiding regional diamond prospecting. The North China Craton is an important region for diamond prospecting in China. At present, two important diamond-bearing kimberlite areas have been found in Mengyin (Shandong Province) and Wafangdian (Liaoning Province). In recent years, the study of typical diamond deposits of different diamond grades shows that the diamond grades in the kimberlite depend on the following two important geological processes: the capture of diamond by kimberlite magma, and the dissolution of diamond by kimberlite magma. A diamond stability field at a temperature of 950~1200℃ and pressure of 4.4~6.1 GPa beneath the North China craton has been proposed. The kimberlitic magma in the Mengyin and the Wafangdian areas passed through the diamond stability field and captured the diamonds during its ascent, and hence become diamondiferous; while the kimberlitic magma in the Tieling and the Hexian areas did not pass through the field, and therefore are barren. As it passed through the diamond stabilization zone, high-grade diamondiferous kimberlite captured more diamonds and indicator minerals that occur with diamond (e.g., pyrope garnet, magnesia-chromite). The low-grade diamondiferous kimberlites capture relatively fewer indicator minerals. These indicator minerals are often involved in diamond formation, some as buffers to control the redox state of the reaction (magma or melt), and some as reactants or products that participate in the reaction. Some indicator minerals (e.g., magnesia-aluminum garnet) further document the metasomatism process by kimberlite magma to diamond after diamond formation. The temperature (T), oxygen fugacity (fO2) and volatiles (H2O and CO2) of kimberlite magma influences the dissolution process of diamond. Amongst these oxygen fugacity's effect is strongest, temperature's effect is weaker, and volatile's effect is the weakest. In the North China Craton, the indicator minerals in kimberlite (pyrope garnet, magnesia chromite) and kimberlite magma parameters (temperature, oxygen fugacity, and volatiles) together constitute the evaluation index of kimberlite diamond primary deposit. © 2020, Science Press. All right reserved.
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页码：2557 / 2573
页数：16
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