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We report the first finding of Ediacaran mafic magmatism in northern Victoria Land of the Ross orogen, Antarctica, based on ca. 600–590 Ma magmatic zircon cores in Cambrian eclogites. The mafic magmatism could be either linked to ca. 615–590 Ma incipient convergent margin magmatism in central segment of the Ross orogen, or ca. 600–580 Ma continental rift‐related volcanism widespread in eastern Australia. The latter is preferred based on the trace‐element compositions distinctive from those of arc‐related basalts and the depleted mantle‐like Hf isotopic compositions of zircon. Our results suggest dual rifting episodes during both the Ediacaran and Cryogenian (ca. 670–650 Ma) in the East Antarctic margin, correlative with those in eastern Australia. A spatial distribution of coeval rifting and subduction along the Ediacaran margin of East Antarctica is readily accounted for by rift inheritance; the upper‐ and lower‐plate geometry resulting from detachment and transform faulting. [ABSTRACT FROM AUTHOR]

This contribution provides an overview on geology, geochronology, and tectonics of Precambrian basement massifs and adjoining Gyeonggi Marginal Belt (GMB), Korea. The three massifs (Gyeonggi, Yeongnam, and Nangrim) record tectonothermal events represented by ∼2.0-1.85 Ga arc-related magmatism and collisional orogenesis, culminating at ∼1.88-1.85 Ga. The oldest (∼2.51 Ga) migmatitic gneisses limitedly occur in the Nangrim and Gyeonggi massifs, suggesting the North China Craton (NCC) affinity of both massifs. The Yeongnam Massif is characterized by the occurrence of ∼1.87-1.86 Ga anorthosite-mangerite-charnockite-granite suite. This anorthositic suite is a late-orogenic product linked to the amalgamation of 'Paleoproterozoic Korean arc' with the North China Craton, forming the Columbia/Nuna supercontinent. The majority of Hf and Nd model ages of basement gneisses are in the range of ∼3.5-2.5 Ga, attesting to the crustal evolution since the Paleoarchean. P-T paths of the Paleoproterozoic basement gneisses are apparently variable, and the Gyeonggi and Yeongnam massifs are characterized by the kyanite-sillimanite and andalusite-sillimanite facies types, respectively. The GMB comprises three fold-and-thrust sub-belts (Imjingang Belt, Taean-Hongseong Complex, and Ogcheon Metamorphic Belt) which are correlative with each other in terms of tectonostratigraphy and detrital zircon geochronology. Two (meta)sedimentary units are diagnostic of this belt: (1) the Neoproterozoic Sangwon Supergroup sharing the provenance with younger rocks in the Ogcheon Belt; and (2) the Devonian turbiditic sequences present in all the three sub-belts. The latter are most distinctive in their detrital zircon age distribution characterized by two major populations at ∼1000-950 Ma and 450-430 Ma. This age pattern as well as the turbiditic lithology is critical for the correlation between the GMB and the Qinling Belt. Taken together, we suggest that the South China Craton-like GMB units are built upon the NCC-like basement (Gyeonggi Massif); this feature is the key to the Qinling-Gyeonggi microcontinent model which accounts for the assembly of a variety of tectonic slivers in the GMB. [ABSTRACT FROM AUTHOR]

To unravel the petrogenesis of a massif-type anorthosite in terms of the crust-mantle geodynamics, we dated zircons separated from six samples from the Sancheong-Hadong ( SH) complex, Korea, using a sensitive high-resolution ion microprobe. The weighted mean 207Pb/206Pb age of two anorthosites is 1862 ± 2 Ma, whereas the ages of the hornblende gabbro and granitic gneiss are 1873 ± 4 Ma and 1875 ± 5 Ma respectively. Zircon rims from mafic granulite and migmatitic gneiss yielded ages of 1860 ± 5 Ma and 1858 ± 4 Ma, respectively, implying that the granulite facies metamorphism and anatexis are associated with anorthosite emplacement. Our results, together with available Re-Os data, are compatible with the ~1.9-1.86 Ga collisional orogeny prevalent in the North China Craton and the Korean Peninsula, and suggest that orogenesis was accompanied by mantle delamination beneath the craton. It is thus likely that the SH anorthositic rocks are a product of late-orogenic magmatism during the post-collisional extension-dominated phase of orogeny. [ABSTRACT FROM AUTHOR]

Elevated heat flow in association with mafic magmatism in an orogenic belt commonly leads to high-temperature, low-pressure (HTLP) metamorphism and the production of granulite-facies assemblages. We studied such a HTLP complex in the vicinity of the Sancheong–Hadong anorthosite-mangerite-charnockite-granite (AMCG) suite, Yeongnam Massif, Korea, in order to constrain the P–T conditions, timing, and duration of metamorphism. This complex primarily consists of massif-type anorthositic-gabbroic bodies emplaced at ∼1.87–1.86 Ga and a series of country rocks comprising orthopyroxene-bearing gneisses as well as anatectic granites and migmatites. Migmatitic gneisses were studied in detail because melt-related features are abundant and well preserved; for example, inclusion-rich peritectic phases such as cordierite or K-feldspar are characteristic for the prograde melt-forming stage, whereas biotite-quartz symplectites mantling garnet or orthopyroxene represent the cooling stage consuming melt. Pseudosection P–T analyses of migmatitic gneisses suggest peak metamorphic conditions of 810–840 °C and 5.9–6.2 kbar, followed by near-isobaric cooling and melt crystallization at  ∼780 °C and  ∼5.5 kbar. SHRIMP (sensitive high-resolution ion microprobe) U–Th–Pb ages of zircon and monazite from six migmatitic gneisses are in the range of 1870–1854 Ma. The oldest age, recorded only in high Y monazite, suggests that prograde metamorphism commenced at ∼1870 Ma. In contrast, melt crystallization had culminated by 1860–1855 Ma producing widespread leucosomes and anatectic granites. Our results suggest that high thermal gradient (∼40 °C km −1 ) attending the granulite-facies metamorphism is attributable to coeval, pulse-like emplacement of anorthositic-gabbroic magmas. Moreover, the HTLP metamorphism lasted over a period of ∼15 Ma, indicating a long-lived process corresponding to the late stage of Paleoproterozoic (∼1.95–1.85 Ga) hot orogenesis in the North China Craton. [ABSTRACT FROM AUTHOR]