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Granites of the southern Mongolia Carboniferous arc : new geochronological and geochemical constraints

Blight, James H.S.; Crowley, Quentin G.; Petterson, Michael G.; Cunningham, Dickson. 2010 Granites of the southern Mongolia Carboniferous arc : new geochronological and geochemical constraints. Lithos, 116 (1-2). 35-52. 10.1016/j.lithos.2010.01.001

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Abstract/Summary

The crust in southern Mongolia is part of the Central Asian Orogenic Belt, a vast accretionary orogen that records the opening and closure of the Palaeo-asian Ocean in the late Proterozoic to Palaeozoic. The crustal evolution of the region is revealed in basement inliers that also contain intrusion-related porphyry ore bodies that are important mineral exploration targets. The Saykhandulaan inlier in Southeast Mongolia is a Devonian–Carboniferous segment of island-arc crust, which is dominantly composed of extrusive and sedimentary lithologies, but which also contains the Oyut Ulaan I-type quartz-monzonite intrusion. A U–Pb zircon age for the Oyut Ulaan monzonite indicates emplacement at 330.0 ± 0.5 Ma. To the east of the Saykhandulaan inlier, intrusive complexes dominate the neighbouring Mandakh inlier. New ages are presented for four of these plutons; the Bronze Fox granodiorite (333.6 ± 0.6 Ma); the Narin Hudag monzonite (333.2 ± 0.6 Ma); the Shuteen quartz monzonite (325.5 ± 1.0 Ma); and the North Mandakh granite (292.3 ± 0.5). The intrusive bodies of the Saykhandulaan and Mandakh inliers have two distinct geochronological and geochemical associations: 1) mid-Carboniferous I-type monzonites that constitute the most easterly intrusive expression of the Southern Mongolia Carboniferous Arc and, 2) Early Permian A-type and peralkaline granites that represent a post-orogenic phase of voluminous granite emplacement. Both groups are significantly younger than the nearby Oyu Tolgoi and Tsagaan Suvarga Cu-porphyry ore bodies, which have previously been dated as early- and late-Devonian respectively. The new data presented here provide constraints on the timing of the transition from island-arc magmatism to post-collisional extension-related magmatism in the region and possible controls on fertile and infertile granitoid intrusions with respect to Cu–Au mineralisation.

Item Type: Publication - Article
Digital Object Identifier (DOI): 10.1016/j.lithos.2010.01.001
Programmes: BGS Programmes 2010 > NERC Isotope Geoscience Laboratory
ISSN: 0024-4937
Date made live: 29 Mar 2010 11:18
URI: http://nora.nerc.ac.uk/id/eprint/9545

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