Abstract
Abstract The diamond-rich Pipe-7 kimberlite found about l0km east of Lattavaram in Anantapur district, Andhra Pradesh in south India is an elongated dyke - like body, that extends over a length of 450 m and has a maximum width of 25 m. It is porphyritic in texture and contains sub-angular to rounded xenoliths of peridotite, garnet-clinopyroxene rocks, websterite, amphibolite, metabasic rocks and granite. Petrographic studies reveal that it is porphyritic in texture and contains euhedral to sub-hedral altered olivine. phlogopite, garnet, clinopyroxene (chrome diopside), chromite, perovskite and ilmenite which are the uneqvivocal primary liquitlus phases whereas serpentine, chlorite, phlogopite, calcite, amphibole, magetite, monticellite, clay minerals and others represent secondary alteration assemblages. Chrome-diopsides and garnets represent an important megacryst suite. The Pipe-7 kimbeerlite has higher CaO and lower MgO, Al2O3, K2O and iron contents compared to rhe other six known kimberlites in the vicinity. Fe/Mg ratio in coexisting garnets and clinopyroxenes, indicates the equilibration temperature for (a) the nodules to be 1040 - 1070°C and for (b) the megacrysts of garnet and clinapyroxene to be 1350°C respectively. Pyrope garnets from titis kimberlite show a positive correlation between CaO and Cr2O3 and are similar in nature to those of the low calcium garnets reported from the diamondiferousSouth African kimberlites.
Published Version
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