Raghavan Nambiar, A. (1988) Petrology of Lamprophyres from Parts of East Garo Hills and West Khasi Hills Districts, Meghalaya. Journal Geological Society of India, 32 (2). 125-136 doi:10.17491/jgsi/1988/320202
| Reference Type | Journal (article/letter/editorial) | ||
|---|---|---|---|
| Title | Petrology of Lamprophyres from Parts of East Garo Hills and West Khasi Hills Districts, Meghalaya | ||
| Journal | Journal Geological Society of India | ||
| Authors | Raghavan Nambiar, A. | Author | |
| Year | 1988 (August 1) | Volume | 32 |
| Page(s) | 125-136 | Issue | 2 |
| Publisher | Geological Society of India | Place | Bangaluru, India |
| URL | |||
| DOI | doi:10.17491/jgsi/1988/320202Search in ResearchGate | ||
| Generate Citation Formats | |||
| Classification | Not set | LoC | Not set |
| Mindat Ref. ID | 17915435 | Long-form Identifier | mindat:1:5:17915435:5 |
| GUID | 0 | ||
| Full Reference | Raghavan Nambiar, A. (1988) Petrology of Lamprophyres from Parts of East Garo Hills and West Khasi Hills Districts, Meghalaya. Journal Geological Society of India, 32 (2). 125-136 doi:10.17491/jgsi/1988/320202 | ||
| Plain Text | Raghavan Nambiar, A. (1988) Petrology of Lamprophyres from Parts of East Garo Hills and West Khasi Hills Districts, Meghalaya. Journal Geological Society of India, 32 (2). 125-136 doi:10.17491/jgsi/1988/320202 | ||
| In | (1988, August) Journal of the Geological Society of India Vol. 32 (2). Geological Society of India | ||
| Abstract/Notes | Abstract Lamprophyres occur as dykes and veins in the Precambrian gneisses and granitoid country rocks along and in the vicinity of tbe Nongchram Fault Zone in East Garo and West Khasi Hills Districts of Meghalaya. They arc genetically associated with feldsputhie ijolites, tinguaites and carbonatites. They are typically melanocratic and contain leucocratic ocelli, spherical or sub-spherical in shape with a centrally disposed core of carbonates and alkali feldspar, mica and clinopyroxene-rich lining. The carbonate-rich inner zones of these zoned ocelli are interpreted as space originally occupied by a gas phase, whereas the outer zones represent late stage liquids. The mineralogy and chemical parameters of these lamprophyres coupled with the common presence of ocelli and megacrysts of mafic minerals and their genetic association with sodic alkaline rocks and carbonatite classify them as alkaline lamprophyres. Petrographically, the holocrystalline rocks can be classified as camptonites and the chilled dyke margins as monchiquites. The occurrence is suggestive of rift-related alkaline magmatism. These alkaline and related rocks together with the ultramafic-alkaline-carbonatite complex of Sung Valley may constitute an ill-defined alkaline province. Their genetic link with Sylhet Trap volcanics cannot be ruled out, as eruption of alkali basalts is generally followed by alkaline intrusions. | ||
Locality Pages
| Locality | Citation Details |
|---|---|
| East Garo Hills District, Meghalaya, India |
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