Are Majhgawan-Hinota pipe rocks truly group-I kimberlite?

Journal of Earth system science

S Nag1¹  A Absar1¹  Ravi Shanker1¹  A Ganguly2²  B P Rawat1¹  G S Singh1¹ 

[1] Geological Survey of India, Northern Region, Lucknow 226 024.$$;Department of Geological Sciences, Jadavpur University, Calcutta 700 032.$$

关键词: Pipe rocks;    mineralogy;    chemistry;    Proterozoic age;    kimberlite;    orangeite;    Majhgawan–Hinota;    Madhya Pradesh.;   

DOI  :  

学科分类：天文学(综合)

来源: Indian Academy of Sciences

【 摘 要 】

The diamond bearing pipe rocks in Majhgawan–Hinota (more than four pipes) occur as intrusives in sandstones of Kaimur Group. These Proterozoic (974 ± 30–1170 ± 20 Ma) intrusive rocks, occupying the southeastern margin of Aravalli craton, were called as `micaceous kimberlite' in tune with the reported kimberlite occurrences from other parts of the world. Judging from the definition of kimberlite, as approved by the IUGS Subcommission on Systematics of Igneous Rocks, it is not justified to call these rocks as `micaceous kimberlite'. Rather the mineralogical assemblages such as absence of typomorphic mineral monticellite (primary), abundance of phlogopite cognate, frequent presence of barite and primary carbonate mostly as calcite coupled with ultrapotassic and volatile-rich (dominantly H2O) nature and high concentration of incompatible elements (such as Ba, Zr, Th, U), low Th/U ratios, low REE and no Eu-anomaly clearly indicate a close similarity with that of South African orangeites. Thus orangeites of Proterozoic age occur outside the Kaapvaal craton of South Africa which are much younger (200 Ma to 110 Ma) in age.

【 授权许可】

Unknown