A Special Issue (Part-II): mafic-ultramafic rocks andalkaline-carbonatitic magmatism and associated hydrothermalmineralization – dedication to Lia N. Kogarko

Thisisthesecondpartofatwo-volumespecialis- sue of Open Geoscience (formerly Central European Jour- nal of Geosciences) that aims to be instrumental in pro- viding an update of Mac-Ultramac Rocks and Alkaline

An Overview of the Carbonatites from the Indian Subcontinent

Carbonatites are carbonate-rich rocks of igneous origin. They form the magmas of their own that are generated in the deep mantle by low degrees of partial melting of carbonated peridotite or eclogite source rocks. They are known to occur since the Archaean times till recent, the activity showing gradual increase from older to younger times. They are commonly associated with alkaline rocks and be genetically related with them. They often induce metasomatic alteration in the country rocks forming an aureole of fenitization around them. They are host for economically important mineral deposits including rare metals and REE. They are commonly associated with the continental rifts, but are also common in the orogenic belts; but not known to occur in the intra-plate regions. The carbonatites are known to occur all over the globe, majority of the occurrences located in Africa, Fenno-Scandinavia, Karelian-Kola, Mongolia, China, Australia, South America and India. In the Indian Subcontinent carbonatites occur in India, Pakistan, Afghanistan and Sri Lanka; but so far not known to occur in Nepal, Bhutan, Bangladesh and Myanmar. This paper takes an overview of the carbonatite occurrences in the Indian Subcontinent in the light of recent data. The localities being discussed in detail cover a considerable time range (>2400 Ma to <0.6 Ma) from India (Hogenakal, Newania, Sevathur, Sung Valley, Sarnu-Dandali and Mundwara, and Amba Dongar), Pakistan (Permian Koga and Tertiary Pehsawar Plain Alkaline Complex which includes Loe Shilman, Sillai Patti, Jambil and Jawar), Afghanistan (Khanneshin) and Sri Lanka (Eppawala). This review provide the comprehensive information about geochemical characteristics and evolution of carbonatites in Indian Subcontinent with respect to space and time

Fluid Inclusion Study of Quartz Xenocrysts in Mafic Dykes from Kawant Area, Chhota Udaipur District, Gujarat, India

Unusual mafic dykes occur in the proximity of the Ambadongar Carbonatite Complex, Lower Narmada Valley, Gujarat, India. The dykes contain dense population of quartz xenocrysts within the basaltic matrix metasomatised by carbonate-rich fluids. Plagioclase feldspars, relict pyroxenes, chlorite, barite, rutile, magnetite, Fe-Ti oxides and glass were identified in the basaltic matrix. Quartz xenocrysts occur in various shapes and sizes and form an intricate growth pattern with carbonates. The xenocrysts are fractured and contain several types of primary and secondary, single phase and two-phase fluid inclusions. The two-phase inclusions are dominated by aqueous liquid, whereas the monophase inclusions are composed of carbonic gas and the aqueous inclusions homogenize to liquid between 226°C and 361°C. Majority of the inclusions are secondary in origin and are therefore unrelated to the crystallization of quartz. Moreover, the inclusions have mixed carbonic-aqueous compositions that inhibit their direct correlation with the crustal or mantle fluids. The composition of dilute CO2-rich fluids observed in the quartz xenocrysts appear similar to those exsolved during the final stages of evolution of the Amba Dongar carbonatites. However, the carbonates are devoid of fluid inclusions and therefore their genetic relation with the quartz xenocrysts cannot be established

A Special Issue (Part-II): Mafic-ultramafic rocks andalkaline-carbonatitic magmatism and associated hydrothermalmineralization - dedication to Lia Nikolaevna Kogarko

This is the second part of a two-volumespecial issueof Open Geoscience (formerly Central European Journalof Geosciences) that aims to be instrumental in providingan update of Mafic-Ultramafic Rocks and Alkaline-Carbonatitic Magmatism and Associated HydrothermalMineralization. Together, these two volumes provide a detailedand comprehensive coverage of the subjects thatare relevant to the research work of P.Comin-Chiaramonti(Italy) and LiaN. Kogarko (Russia) towhomPart-I and Part-II have been respectively dedicated.To a significant extent, the development of advanced samplingtechnologies related to alkaline and carbonatiticmagmatism by Lia N. Kogarko, has allowed geoscientiststo measure and sample the deep crust of the planet notonly for the exploration for the mineral deposits, but alsoto answer basic scientific questions about the origin andevolution of alkaline rocks (kimberlites, lamproites and relatedrocks associated with carbonatites). The papers presentedin this Part-II of the special issue cover the petrologyand geochemistry of the rocks collected from the surfaceand penetrated by drilling. Lia Kogarko proposed anew theory for the evolution of alkaline magmatism in thegeological history of the Earth – that the appearance of alkalinemagmatism at the Archaean-Proterozoic boundary(~2.5 – 2.7 Ga), and its growing intensity, was related tochanges in the geodynamic regime of the Earth and oxidationof the mantle due to mantle-crust interaction