T283 From Oceanic Subduction to Inter-Continental Collision: Examples of Convergent Margin Processes in Non-Collisional and Collisional Settings (Posters)

Wednesday, 25 September 2019
9:00 AM - 6:30 PM
Hall AB, North Building

LATE NEOARCHEAN SLAB ROLLBACK IN THE JIAOLIAO MICROBLOCK, NORTH CHINA CRATON: CONSTRAINTS FROM ZIRCON U–PB GEOCHRONOLOGY AND GEOCHEMISTRY OF THE YISHUI COMPLEX, WESTERN SHANDONG PROVINCE

Paper number: T283-1
Program: Technical Sessions
Time: 9:00 AM – 6:30 PM

Authors

Abstract

Earth’s plate tectonic system was initiated between 3.0 and 2.5 Ga and became the dominant regime for crustal growth and differentiation. However, it is unclear whether subduction–accretion processes, including slab rollback, occurred regionally in the area of the western Shandong Province Granite–Greenstone Terrane of the North China Craton (NCC) during the early development of plate tectonics. We quantified petrology, whole-rock geochemistry, and zircon U–Pb–Hf isotopes for felsic, mafic, and ultramafic rocks from the Yishui Complex (YC) in the NCC to constrain the origin of these rocks and the associated tectonic setting(s). The granites yield 207Pb/206Pb ages of 2509 ± 20 to 2484 ± 26 Ma, and magmatic zircon grains from these rocks have εHf(t) values of 0.6–6.4. The coeval mafic–dioritic rocks represent the fractional crystallization products of a primary magma that was derived from low-degree (<7%) partial melting of a metasomatized mantle source. The granodiorites were derived from the partial melting of oceanic slab material, with slab melts being contaminated by mantle wedge material during their ascent. The high-K granites represent the crustal reworking products of regional tonalite–trondhjemite–granodiorite and sedimentary rocks. Late Neoarchean magmatism in the YC was related to slab subduction, and slab rollback at ~2.50 Ga led to the generation of potassic rocks, coeval mafic–ultramafic xenoliths, and granulite metamorphism with a counterclockwise P–T–t path in the Yishui area.

Geological Society of America Abstracts with Programs. Vol. 51, No. 5

doi: 10.1130/abs/2019AM-336310

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