In:
GSA Bulletin, Geological Society of America, Vol. 133, No. 9-10 ( 2021-09-01), p. 2171-2188
Abstract:
Accompanying Gondwana assembly, widespread but diachronous Ediacaran–early Paleozoic magmatism of uncertain origin occurred along the supercontinent's proto-Tethyan margin. We report new geochemical, isotopic, and geochronological data for Cambrian magmatic rocks (ca. 500 Ma) from the Gondwana-derived North Lhasa terrane, located in the present-day central Tibetan Plateau. The magmatic rocks are composed of basalts, gabbros, quartz monzonites, granitoids (with mafic microgranular enclaves), and rhyolites. Nd-Hf isotopic and whole-rock geochemical data indicate that these rocks were probably generated by mixing of mantle-derived mafic and crust-derived felsic melts. The mantle end-member volumes of mafic, intermediate, and felsic rocks are ∼75%–100%, 50%–60%, and 0–30%, respectively. Integration of our new data with previous studies suggests that the North Lhasa terrane experienced long-term magmatism through the Ediacaran to Ordovician (ca. 572–483 Ma), with a magmatic flare-up at ca. 500 Ma. This magmatism, in combination with other Ediacaran–early Paleozoic magmatism along the proto-Tethyan margin, was related to an Andean-type arc, with the magmatic flare-up event related to detachment of the oceanic slab following collisional accretion of Asian microcontinental fragments to northern Gondwana. Diachroneity of the proto-Tethyan arc system along the northern Gondwanan margin (ca. 581–531 Ma along the Arabian margin and ca. 512–429 Ma along the Indian-Australian margin) may have been linked to orogenesis within Gondwana. The North Lhasa terrane was probably involved in both Arabian and Indian-Australian proto-Tethyan Andean-type orogens, based on its paleogeographic location at the northern end of the East African orogen.
Type of Medium:
Online Resource
ISSN:
0016-7606
,
1943-2674
Language:
English
Publisher:
Geological Society of America
Publication Date:
2021
detail.hit.zdb_id:
2028776-8
detail.hit.zdb_id:
2008165-0
detail.hit.zdb_id:
449720-X
detail.hit.zdb_id:
1351-1
SSG:
13
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