A RECORD OF LAMPROPHYRIC ROCKS AROUND CHHOTA UDEPUR VADODARA DISTRICT AND ITS PETROLOGICAL AND GEOLOGICAL COMPARISON WITH OTHER OCCURRENCES OF LAMPROPHYRES IN GUJARAT

摘要

Lamprophyric rocks related to Deccan Volcanism occur as extensive dykes around Chhota Udepur area within Precambrian granite gneiss country rocks. On the basis of mineralogy, petrography and geochemistry these are classified as 'Lamprophyric Rocks "of tephrite-basanite composition. The Chhota Udepur 'Lamprophyric Rocks' (CUL) are depleted in MgO, Ni and Cr compared to 'Average Alkali Lamprophyre' (AL). They are enriched in LILE, LREE and depleted in HREE which are contrary to 'AL' and 'Girnar Lamprophyric Mocks'. The generalised character of CUL as evidenced by their petrography and geochemistry indicates their origin from a metasomatised mantle in the latest phase of Deccan Volcanism.