Age and petrogenesis of Mingshui-Shuangjingzi granites from the northern Beishan area, northwest China, and their implications for tectonic evolution

• The Mingshui and Shuangjingzi granitic plutons are exposed in the northern Beishan area, in the southern Central Asia Orogenic Belt. U-Pb zircon dating indicates that Mingshui secondary intrusive lithosfacies and Shuangjingzi quartz monzodiorite formed at 328 ± 2 Ma and 272 ± 2 Ma, respectively. The former is composed of grey white monzogranites and potassic altered flesh red monzogranites. Geochemistry indicates they are calc-alkaline I-type granites. Shuangjingzi granites are mainly composed of unfractionated calc-alkaline I-type quartz monzodiorite, granodiorite and monzogranite. The Mingshui grey white monzogranites with negative initial εNd (–2.0 to–1.7) and moderate initial 87Sr/86Sr values (0.706740 to 0.710092) were probably derived from mixing of the depleted mantle (juvenile) component and the Palaeoproterozoic–Archean crust (or sedimentary) component and represent volcanic arc granites. The Shuangjingzi quartz monzodiorites are most likely derived from mafic to intermediate igneous protolith and represent post-collisional granites. This work, combined with the regional geology, suggests the Palaeo-Asian Ocean closed between 328 Ma and 272 Ma in the northern Beishan area.

Ämnesord

NATURVETENSKAP  -- Geovetenskap och miljövetenskap (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences (hsv//eng)

Nyckelord

Central Asia Orogenic Belt

Beishan

Palaeozoic

granite

post-collisional

geochemistry

geochronology

Geology

geologi

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