Identifying the source characteristics of silicic magmas (SiO2 >65 wt%) is significant for revealing the nature of the crust and recycling processes under a continental arc zone. Herein, we present a comprehensive dataset of zircon U-Pb-Hf-O isotopes and whole-rock major and trace elements as well as Nd isotopes for two groups of Neoproterozoic silicic volcanic magmas from the Mianning area in the western Yangtze block (South China) in order to place systematic constraints on the heterogeneous crustal sources as well as crustal reworking and recycling processes of a Neoproterozoic continental magmatic arc during the evolution of the supercontinent Rodinia. The studied dacites and rhyolites, dated at ca. 815–811 Ma, are generally characterized by high SiO2 (66.87–80.02 wt%) but low MgO (0.11–0.81 wt%), Mg# (8.94–30.0), Cr (0.50–4.54 ppm), and Ni (1.10–4.98 ppm) contents, enriched light rare earth elements (LREEs) and large ion lithophile elements (LILEs; e.g., Rb, K), and depleted high field strength elements (HFSEs; e.g., Nb, Ta, Ti, and P), implying a source with continental crust affinity. Considering the contrasting whole-rock Nd and zircon Hf-O isotopic characteristics, these silicic volcanic rocks can be divided into two groups that originated from heterogeneous crustal sources. Group 1 dacites display relatively depleted whole-rock Nd (εNd[t] = +0.51 to +1.65) and zircon Hf (εHf[t] = +1.80 to +8.86) isotopes as well as submantle zircon O isotopes (δ18O = 3.95‰–4.63‰), and therefore, they were likely formed by recent melting of juvenile mafic arc lower crust, which was supplemented by mantle wedge melts metasomatized by predominantly subducted slab melts. Group 2 dacites and rhyolites have negative whole-rock εNd(t) (−4.05 to −2.12), low and variable zircon εHf(t) (−2.84 to +3.44), and highly variable zircon δ18O values (4.50‰–9.90‰), which could be derived from a relatively ancient and enriched crustal source heated by melts from juvenile lower crust or metasomatized mantle. We propose that the silicic volcanics in this study represent the simultaneous crustal melting of different magmatic reservoirs under a continental arc zone, which are responsible for the petrological and geochemical diversities of these Neoproterozoic silicic magmas. In combination with a compilation of previous data from nearby Neoproterozoic silicic igneous rocks, the diverse silicic magmas showing distinct Nd-Hf-O isotopes can be regarded as the products of primarily crustal reworking and recycling from heterogeneous crust-derived components (i.e., juvenile and ancient/evolved crust sources), and therefore, they preserve comprehensive information about crustal differentiation and enrichment in a continental arc setting.

The Qilian Shan, located in the northeastern Tibetan Plateau, is an intraplate orogenic belt that underwent several episodes of fold and thrust deformation, particularly during the Mesozoic and Cenozoic. However, the deformation styles and relationships between the basin and mountains remain controversial. Therefore, in the current study, we conducted detailed field mapping of the sedimentary basins in Sunan and Huangcheng, and observed three episodes of compressive tectonic activity. We also restored a deformed section to determine the shortening rate of the Cretaceous sedimentary Sunan Basin. The first thrust episode, during the Paleogene, involved a southwestward thrust motion, comprising the Yumu Shan and Gaizhangdaban thrust systems. The second Neogene episode involved the northeastern thrust belt in the northern Qilian Shan, which comprises the Northern Qilian thrust system. The third episode produced NW-trending strike-slip activity that became the major tectonic deformation style; thus, the entire block rotated clockwise. Additionally, the restored section revealed that the Cretaceous strata have been shortened by ∼3.56%. Collectively, these results indicate that the Sunan and Huangcheng area on the northeastern Tibetan Plateau is influenced by the far-field effects of the collision between the Indian and Asian continents, as well as the effects of intraplate orogenic processes related to the collision of the Alashan Block and the Qilian Shan. Therefore, the current study has defined the deformation style in the northeastern Qilian Shan region, so we wish to give a clarification of the tectonic evolution and forecast the tectonic propagation in the Qilian Shan region.

Elucidating the petrological and geochemical characteristics of continental arc crustal fragments can provide unique insights into the magmatic evolutional path and physicochemical conditions (e.g., P−T−H₂O) of continental magmatic arcs. This contribution provides a comprehensive set of petrological, mineralogical, geochronological, and geochemical data for the Neoproterozoic Nanba intrusive complex of the western Yangtze Block, South China, which features well-exposed middle−upper crustal sections of the Neoproterozoic continental magmatic arc, to evaluate their magmatic source and fractionation process. The Neoproterozoic Nanba intrusive complex, composed of cumulate gabbros, hornblende gabbros, gabbro-diorites, diorites, granodiorites, K-feldspar granites, and monzogranites, was emplaced at ca. 796−790 Ma. The different lithologies of the Nanba intrusive complex display relatively homogeneous Sr-Nd-Hf isotopes, which indicates a cogenetic evolutional process. The predominantly depleted isotopic characteristics, together with high values of Ba, Rb/Y, and Ba/La, demonstrate that these rocks mainly originated from a subduction fluid−metasomatized mantle source. Petrological and geochemical characteristics, as well as hornblende thermobarometric data, collectively support that the ca. 796−790 Ma Nanba intrusive complex, following the calc-alkaline trend, was dominated by the wet cogenetic fractionation of hornblende accompanied by plagioclase and accessory minerals beneath the middle−upper crustal levels (2.4−4.7 kbar). The cumulate gabbros represent the residue of accumulated hornblende + plagioclase + Fe-Ti oxides from fractionated basaltic melts. The high-SiO₂ K-feldspar granites and monzogranites display complementary trace elements, which represent residual silicic cumulates and extracted interstitial liquids in the shallower crystal mush reservoir, respectively. In combination with previous studies, we propose that the middle−upper crustal sections of the Neoproterozoic continental arc of the western Yangtze Block underwent hornblende-dominated fractionation that was followed by significant crystal-liquid separation, which led to the genesis of high-SiO₂ melts at the shallower crustal level. The cogenetic evolution played a significant role in molding the petrological and geochemical diversity of Neoproterozoic igneous rocks and the differentiation process of continental arc crust in the western Yangtze Block.