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[Display omitted] • The sedimentation of the Huili Group lasted from ca. 1.1 Ga to 1.0 Ga. • A drastic provenance shift occurred within the Huili Group at 1.04 Ga. • The tectonic regime evolved from passive margin to convergence setting. • The Yangtze Block was not yet part of the Rodinia in the latest Mesoproterozoic. The Huili Group, one of the most representative late Mesoproterozoic strata in the Yangtze Block, bears key information for the tectonic history of the South China Block in the context of the supercontinent cycle. We present an integrated dataset involving field observation, petrology, detrital zircon U-Pb dating, and Hf isotope analyses for the Huili Group. Our new detrital zircon U-Pb ages, in combination with available magmatic age data, confirm that the Huili Group was mainly deposited at ca. 1.1–1.0 Ga. The lower Huili Group is characterized by subrounded to rounded detrital zircon grains with age intervals of 2.80–2.40 Ga (~21%), 2.34–1.72 Ga (~64%), and 1.68–1.19 Ga (~14%). In contrast, zircon grains from the upper Huili Group have variable morphologies and yield two pronounced age populations of 2.00–1.25 Ga (~50%; subrounded to rounded grains) and 1.2–1.0 Ga (~46%; euhedral to subhedral grains). The majority of zircon grains have ε Hf (t) values and depleted mantle two-stage (T DM2) model ages comparable to those of magmatic rocks or older sediments in the Yangtze Block. Multiple sources are suggested to have contributed older detrital zircon grains to the lower Huili Group, whereas the upper part received greater proportions of zircon grains with ages close to or equal to the depositional age from proximal magmatic sources. This observation indicates a drastic provenance shift most likely occurred within the Huili Group at ~1.04 Ga. Through reappraising our detrital zircon results and available geological datasets, we suggest that the terrigenous clastic and carbonate rocks of the lower-middle Huili Group were deposited on a passive continental margin, but the upper volcano-sedimentary sequences were formed in a back-arc extensional setting. We further propose that the Yangtze Block was spatially separated from (i.e., not yet part of) the Rodinia supercontinent during the sedimentation of the Huili Group, supporting that a global supercontinent did not exist yet in the late Mesoproterozoic. [ABSTRACT FROM AUTHOR]

The Early Permian strata of the Hongliuhe Formation are located in the Beishan orogenic collage, a tectonically significant region between the Tianshan orogen and the Southern Mongolian accretionary system, of the Central Asian Orogenic Belt (also called the Altaids). Stratigraphic reconstruction of the formation shows a general fining upwards sequence of rhythmically interbedded sandstones and siltstones with thick basal successions of conglomerates, all unconformably overlying an earlier mid-Paleozoic volcanic assemblage. The clast lithotypes of conglomerates successively change from being polymictic metamorphic tectonites at the base to a nearly monomictic granitoids mid-section, illustrating the unroofing sequence of an arc-related provenance. The intra-oceanic Gongpoquan composite arc that comprises most of the central Beishan fits the clast-lithotype profile of the conglomerates, and is the most probable provenance. The Hongliuhe Formation stratigraphy experienced a thin-skinned fold-and-thrust belt style of deformation that has a consistent southward vergence. Deformation in the lower stratigraphic levels created thrust imbrication of formation-scale blocks, each separated by steep, north-over-south brittle–ductile shear zones. The blocks are internally deformed with large-scale folding, with one significant block containing a sheath fold 15 km in breadth. The upper stratigraphic levels accommodated strain through low-angle thrust ramping, shear folding, imbricate fanning and duplexing. This indicates that the Hongliuhe Formation was syn-orogenically deposited in a progressively deepening terrestrial- to nearshore environment within the Gongpoquan composite arc. Our observations and data indicate that the basin overlies an earlier Paleozoic suture zone. This implies that the northern half of the Gongpoquan composite arc overrode the southern half in a fault system reactivation centered about this zone of weakness, and created a stratigraphic and structural response consistent with a subduction- or collision-driven fold-and-thrust belt. Its southward structural vergence is supporting evidence of a north-dipping subduction-related fault system under the northern Gongpoquan. The timing of both the genesis of the Hongliuhe Formation and this deformation event coincides with the subduction of the Liuyuan Ocean or docking of the Dunhuang block further south, at the southern margin of the Gongpoquan composite arc. [ABSTRACT FROM AUTHOR]

Abstract: Amphibolites occur in a number of localities in the Cathaysia Block, some of them have been migmatised and their protoliths represent basaltic magmas erupted in various tectonic settings. Four migmatised amphibolites were collected from Jiangxi and Fujian Provinces. Cathodo-luminescence images of zircons extracted from the representative amphibolites show unzoned or sector-zoned structure. LA-ICP-MS analysis indicates that most zircons have high Th/U ratios and yield U–Pb zircon ages of 446±5, 435±2, 434±4 and 423±2Ma, respectively. Lu–Hf isotopic analysis on these zircons gives Hf model ages ranging from 900 to 1200Ma. Based on lithological observations and previously published geochronological data, we interpret that these U–Pb ages record an important tectonothermal event that led to the migmatization. This early Paleozoic (Caledonian) tectonothermal event in the Southeastern China has a great tectonic implication for the evolutionary history of the Cathaysia Block. [ABSTRACT FROM AUTHOR]