RB-SR AGE OF THE METALUMINOUS GRANITOIDS OF SOUTH KHASI BATHOLITH, MEGHALAYA - IMPLICATIONS ON ITS GENESIS AND PAN-AFRICAN ACTIVITY IN NORTHEASTERN INDIA
Ap. Selvam et al., RB-SR AGE OF THE METALUMINOUS GRANITOIDS OF SOUTH KHASI BATHOLITH, MEGHALAYA - IMPLICATIONS ON ITS GENESIS AND PAN-AFRICAN ACTIVITY IN NORTHEASTERN INDIA, Journal of the Geological Society of India, 46(6), 1995, pp. 619-624
Metaluminous granitoids of the South Khasi batholith (SKB) in the West
Khasi Hills district of Meghalaya define a Rb-Sr whole-rock isochron
age of 757 +/- 60 Ma, with (Sr-87/Sr-86)(i) Of 0.71069 +/-0.00092. SKB
and other granitoids of Meghalaya like Mylliem, Nongpoh and Kyrdem ha
ve many common features such as the presence of basic enclaves of horn
blende gneiss and amphibolite, late- to post-tectonic nature, predomin
ance of biotite amongst mafic silicates, overall metaluminous nature a
nd high (Sr-87/Sr-86)(i) of more than 0.709. All these indicate much s
imilarity in the genesis of their melts due to partial melting of lowe
r crustal rocks. The Rb-Sr isochron ages of SKB and other granitoids i
n Meghalaya Feint to a major tectonomagmatic activity during ca. 760-4
80 Ma, which is almost coeval with ca. 800-500 Ma Mid-Upper Pan-Africa
n activity. The data, thus imply the possible imprint of the widesprea
d Pan-African activity in northeastern India, besides southern India.