Petrography and major element chemistry of mafic dykes in the Nagar Parkar Igneous Complex, Tharparkar, Sindh
Keywords:
Nagar Parker; Late Proterozoic Granites; Mafic dykes; AlkalineAbstract
The Nagar Parkar igneous complex consists of a variety of Late Proterozoic granitic rocks emplaced in a basement of amphibolitic rocks. These were intruded by mafic rocks that range from veins to dykes commonly no more than 300×5 m in surface exposures; but a few are thicker and longer, with one extending up to 2 km. The dykes can be divided into two groups: a possibly earlier one of amphibole bearing rocks, and a later group of titanium augite-bearing rocks. The rocks are grey to black, fine- to medium-grained, and commonly porphyritic. In addition to amphibole or augite, they also contain zoned plagioclase (andesine-labradorite, commonly saussuritized), opaque oxides, apatite, sphene, and secondary minerals. Some of the augite-bearing rocks also contain olivine. The two groups of rocks are alkaline, similar in major element chemistry, and derived from differentiated magma(s).
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