Contrasting petrogenesis of spatially related carbonatites from Samalpatti and Sevattur, Tamil Nadu, India

0475325 - GLÚ 2018 RIV NL eng J - Článek v odborném periodiku
Ackerman, Lukáš - Magna, T. - Rapprich, V. - Upadhyay, D. - Krátký, O. - Čejková, B. - Erban, V. - Kochergina, Y. V. - Hrstka, Tomáš
Contrasting petrogenesis of spatially related carbonatites from Samalpatti and Sevattur, Tamil Nadu, India.
Lithos. 284/285, 1 July (2017), s. 257-275. ISSN 0024-4937. E-ISSN 1872-6143
Institucionální podpora: RVO:67985831
Klíčová slova: carbonatite * geochemistry * Samalpatti * Sevattur * silicocarbonatite * Sr–Nd–Pb–C–O isotopic systematics
Obor OECD: Geology
Impakt faktor: 3.857, rok: 2017

Two Neoproterozoic carbonatite suites of spatially related carbonatites and associated silicate alkaline rocks from Sevattur and Samalpatti, south India, have been investigated in terms of petrography, chemistry and radiogenic–stable isotopic compositions in order to provide further constraints on their genesis. The cumulative evidence indicates that the Sevattur suite is derived from an enriched mantle source without significant post-emplacement modifications through crustal contamination and hydrothermal overprint. The stable isotopic compositions confirm mantle origin of Sevattur carbonatites with only a modest difference to Paleoproterozoic Hogenakal carbonatite. On the contrary, multiple processes have shaped the petrography, chemistry and isotopic systematics of the Samalpatti suite. These include pre-emplacement interaction with the ambient crustal materials with more pronounced signatures of such a process in silicocarbonatites. Calc-silicate marbles present in the Samalpatti area could represent a possible evolved end member due to the inability of common silicate rocks (pyroxenites, granites, diorites) to comply with radiogenic isotopic constraints. In addition, Samalpatti carbonatites show a range of C–O isotopic compositions that could be indicative of massive hydrothermal interaction with carbonated fluids. Unusual high-Cr silicocarbonatites, discovered at Samalpatti, seek their origin in the reaction of pyroxenites with enriched mantle-derived alkali-CO₂-rich melts, as also evidenced by mantle-like O isotopic compositions. We emphasise that, beside common carriers of REE like apatite, other phases may be important for incompatible element budgets, such as mckelveyite–(Nd) and kosmochlor, found in these carbonatites. Future targeted studies, including in-situ techniques, could help further constrain temporal and petrologic conditions of formation of Sevattur and Samalpatti carbonatite bodies.
Trvalý link: http://hdl.handle.net/11104/0272156