Using Zircon Geochronology to Unravel the History of the Naga Hills Ophiolite

Tuesday, 16 December 2014
Tara Roeder1, Jonathan C Aitchison2, Geoffrey L Clarke1, Trevor R Ireland3, Ali Ao4 and Santanu K Bhowmik5, (1)University of Sydney, Sydney, NSW, Australia, (2)University of Sydney, School of Geosciences, Sydney, NSW, Australia, (3)Australian National University, Canberra, Australia, (4)Indian Institute of Technology Kharagpur, Geology & Geophysics, Kharagpur, India, (5)University of Sydney, Sydney, Australia
Outcrops of the Naga Hills Ophiolite (NHO), a possible eastern extension of the ophiolitic belt running along the India-Asia suture, in Northeast India include a full suite of ophiolitic rocks. The ophiolite has been dated Upper Jurassic based on radiolarian studies of the unit (Baxter et al., 2011) but details of its emplacement onto the Indian margin have not been the subject of detailed investigation.

Conglomerates of the Phokphur Formation unconformably overlie an eroded surface on top of dismembered ophiolite fragments and include sediments sourced from both the ophiolite and the margin of the Indian subcontinent. Notably no Asian margin-derived detritus is recognised (similar to the Liuqu conglomerates of Tibet (Davis et al., 2002)). Thus, a detailed study of the Phokphur sediments can produce valuable details of the NHO history, including constraining the timing of ophiolite emplacement. Studies of detrital sandstone petrography confirm a recycled orogen provenance for the Phokphur Formation and thus serve as validation of the methods of Dickinson and Suczek (1979) and Garzanti et al. (2007). Detrital zircon data provides further insight as to the age of source rocks of Phokphur sediments and help to further constrain the timing of ophiolite emplacement. We present results of sedimentary and detrital zircon geochronology analyses of Phokphur sediments from outcrops near the villages of Salumi and Wazeho as a contribution to furthering research on aspects of the India-Asia collision.

Baxter, A.T., et al. 2011. Upper Jurassic radiolarians from the Naga Ophiolite, Nagaland, northeast India. Gondwana Research, 20: 638-644.

Davis, A.M., et al. 2002. Paleogene island arc collision-related conglomerates, Yarlung–Tsangpo suture zone, Tibet. Sedimentary Geology, 150: 247-273.

Dickinson, W.R. and Suczek, C.A., 1979. Plate tectonics and sandstone compositions. Am. Assoc. Pet. Geol. Bull., 63, 2164-2182, (1979).

Garzanti, E., et al., 2007. Orogenic belts and orogenic sediment provenance. The Journal of Geology, 115: 315-334.