V. E. Glushkova, I. S. Peretyazhko, E. A. Savina, E. A. Khromova
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引用次数: 0
Abstract
This paper reports the olivine-group minerals from melilite–nepheline paralavas of two combustion metamorphic (CM) complexes of Mongolia. The paralavas formed by thermal alterations of sedimentary rocks due to multistage modern and ancient (since the Quaternary) wild coal fires. The decomposition products of the olivine solid solution into Ca-bearing fayalite and kirschsteinite have been found in paralavas of the Khamaryn–Khural–Khiid CM complex. Apart from these minerals, members of isomorphic series forsterite–fayalite, and monticellite–kirschsteinite, and simplectite-like intergrowths of kirschsteinite with nepheline were identified in the paralavas of the Nyalga CM complex. The studied minerals differ in structural features, Mg# value, and crystallization temperature as a consequence of local variations in formation conditions and composition of silica-undersaturated Ca-rich mafic melts initial for melilite–nepheline paralavas. The olivines of the monticellite–kirschsteinite series reaching 86 mol % of kirschsteinite end-member occur only in paralavas bearing xenoliths of thermally modified carbonate-silicate sedimentary rocks. The crystallization of these olivines together with gehlenitic melilite took place through interaction between mafic paralava melts and xenoliths of marly limestones with large variations in content of silicate (clay–feldspar) admixture.
摘要 本文报告了蒙古两个燃烧变质岩群（CM）熔融-涅盘状副岩体中的橄榄石族矿物。这些副岩是由现代和远古（自第四纪以来）多级野煤火引起的沉积岩热变形成的。在 Khamaryn-Khural-Khiid CM 复合体的副岩中发现了橄榄石固溶体的分解产物，即含 Ca 的法叶腊石和基氏石。除这些矿物外，在聂雅嘎 CM 矿群的副岩体中还发现了同构系列的芒硝-法安石、芒硝-钾长石，以及钾长石与霞石的类单斜辉石互生。所研究的矿物在结构特征、Mg#值和结晶温度方面存在差异，这是因为形成条件和富含二氧化硅-过饱和钙的黑云母熔体成分的局部变化导致了黑云母-霞石副熔岩的形成。只有在热改造碳酸盐-硅酸盐沉积岩的副岩中才会出现蒙脱石-柯氏橄榄石系列橄榄石，其中柯氏橄榄石的终成体含量高达 86 摩尔%。这些橄榄石与gehlenitic melilite的结晶是在黑云母副熔岩熔体与硅酸盐（粘土长石）掺杂物含量变化较大的泥质灰岩侧晶之间的相互作用下形成的。
期刊介绍：
Geology of Ore Deposits is a periodical covering the topic of metallic and nonmetallic mineral deposits, their formation conditions, and spatial and temporal distribution. The journal publishes original scientific articles and reviews on a wide range of problems in theoretical and applied geology. The journal focuses on the following problems: deep geological structure and geodynamic environment of ore formation; distribution pattern of metallogenic zones and mineral deposits; geology and formation environment of large and unique metallic and nonmetallic deposits; mineralogy of metallic and nonmetallic deposits; physicochemical and isotopic characteristics and geochemical environment of ore deposition; evolution of ore-forming systems; radiogeology and radioecology, economic problems in exploring, developing, and mining of ore commodities.
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