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Metamorphic core complexes are developed in crustal activity belts at the continental margins or within continents, and their main tectonic feature is that the ductile middle crust is exhumed at the surface. The deformation properties are closely related to the geodynamic process affecting the continental crust. However, the evolution of the metamorphic core complexes after their formation is still unclear. The Cretaceous Liaonan metamorphic core complex developed in the eastern North China craton provides an ideal environment to study its evolution. In this study, we estimate the paleo-temperature and paleo-stress at the time of formation of the metamorphic core complex dynamical recrystallization of quartz and calculate the thermo-rheological structure of the present Liaonan metamorphic core complex by one-dimensional steady-state heat conduction equation and power-creep law. The results show that compared with the Cretaceous period, the geothermal heat flow value of the present Liaonan metamorphic core complex decreases from 70–80 mW/m2 to 49.4 mW/m2, the thermal lithosphere thickness increases from 59–75 km to 173 km, and the brittle transition depth increases from 10–13 km to about 70 km, showing coupling of the crust–mantle rheological structure. We speculate that the evolution of the thermo-rheological structure of the Liaonan metamorphic core complex is possibly caused by rapid heat loss or lithospheric mantle flow in the Bohai Bay Basin. [ABSTRACT FROM AUTHOR]

The Taoxi dome stands out as a rotated-circular structure on maps of the Wuyi terrane, south China. The origin and tectonic activity analysis of the Taoxi dome is a window to understand the tectonic framework and aggregation process of the Wuyi terranes in the Cathaysia block. Our field observations demonstrated that two major phases of deformation, counterclockwise rotation and dome uplift, were recorded in the Taoxi dome. Geochronological data indicated that the counterclockwise rotation was initiated at about 422 Ma as a result of a sinistral slide collision between the North Wuyi terrane and the South Wuyi terrane along the Nanping–Ninghua tectonic belt during the Caledonian. Zircon dating ages of the intrusions developed in the Taoxi dome suggested that the Taoxi dome had undergone at least two strong upheavals and the uplift of the Taoxi dome was active during the periods 229–222 Ma and 158–100 Ma. Geochemical data indicated that the intrusions developed in the Taoxi dome had characteristics of high silica (SiO2 > 70 wt.%) and belonged to the A2-type granites, which suggest that the Taoxi dome was long governed by a tectonic setting of post-collisional or anorogenic magmatism since the Caledonian. The strong movement of the Caledonian rotation and coeval strike-slip movement in the Wuyi terranes suggests that a slide rotation may have been a major characteristic in response to the rifting process of micro-terranes during the late Paleozoic in the Cathaysia block. [ABSTRACT FROM AUTHOR]

Whole-rock and apatite geochemical analyses and zircon U–Pb dating were carried out on the lamprophyres in the world-class Zhuxi W–Cu skarn deposit in northern Jiangxi, South China, in order to understand their origin of mantle sources and their relationship with the deposit, as well as metallogenic setting. The results show the lamprophyres were formed at ca. 157 Ma, just before the granite magmatism and mineralization of the Zhuxi deposit. These lamprophyres have from 58.98–60.76 wt% SiO2, 2.52–4.96 wt% K2O, 5.92–6.41 wt% Fe2O3t, 3.75–4.19 wt% MgO, and 3.61–5.06 wt% CaO, and enrichment of light rare earth elements (LREE) and large-ion lithophile elements (LILE), and depletion of high-field-strength elements (HFSE). Apatites in the lamprophyres are enriched in LREE and LILE, Sr, S, and Cl, and have 87Sr/86Sr ratios ranging from 0.7076 to 0.7078. The conclusions demonstrate that the lithospheric mantle under the Zhuxi deposit was metasomatized during Neoproterozoic subduction. Late Jurassic crustal extension caused upwelling of the asthenospheric mantle and consecutively melted the enriched lithospheric mantle and then crustal basement, corresponding to the formation of lamprophyres and mineralization-related granites in the Zhuxi deposit, respectively. [ABSTRACT FROM AUTHOR]

The Axi low-sulfidation (LS) epithermal deposit in northwestern China is the result of geological controls on hydrothermal fluid flow through strike-slip faults. Such controls occur commonly in LS epithermal deposits worldwide, but unfortunately, these have not been quantitatively analyzed to determine their spatial relationships with gold distribution and further guide mineral prospecting. In this study, we conduct a 3D mineral prospectivity modeling approach for the Axi deposit involving 3D geological modeling, 3D spatial analysis, and prospectivity modeling. The spatial analysis of geometric features revealed the gold mineralization trends in convex segments (0–20 m) with a specific distance from fault 2, the lower interface of late volcanic phase, and the upper interface of phyllic alteration with steep slopes (>65°), implying that gold deposition was significantly controlled by the morphological characteristics and distance fields of geologic features. The present alteration–mineralization zone at Axi has a larger width in bending sites (sections No. 35–15 and No. 40–56) than elsewhere, indicating the location of two fluid conduits extending to depth. The prediction-area plots and receiver operating characteristic curves demonstrated that (genetic algorithm optimized support vector regression (GA-SVR)) outperformed multiple nonlinear regression and fuzzy weights-of-evidence, which was proposed as a robust method to solve complicated nonlinear and high-dimensional issues in prospectivity modeling. Our study manifests spatial controls of structure, host rock, and alteration on LS epithermal gold deposition, and highlights the capability of GA-SVR for identifying deposit-scale potential epithermal gold mineralization. [ABSTRACT FROM AUTHOR]