The subduction history of the Paleo-Tethys Ocean is constrained by geological and paleomagnetic evidence, particularly the collision between the North China and South China blocks. Yet, its influence on the Qaidam Block and the persistence of a remnant oceanic basin, now represented by the Songpan–Ganzi terrane, remain poorly understood. We integrate detrital zircon U–Pb ages from the South Qilian region, geochronological and thermochronological data of Permian–Jurassic arc plutons from the Qaidam Block, and paleomagnetic results from the Qaidam and North Qiangtang blocks to reconstruct the tectonic response to Paleo-Tethys subduction. Our results indicate that the Paleo-Tethys oceanic plate subducted northward beneath the Qaidam Block at a low angle, causing basement uplift and the formation of the South Qilian retro-arc foreland basin. The subsequent collision between the North Qiangtang and Qaidam blocks at ca. 240 Ma preceded the final amalgamation of the North and South China blocks. Because the Qiangtang and Indochina blocks were connected to the South China Block, this configuration produced an inverted-triangle-shaped remnant ocean basin or intercontinental rift—the present-day Songpan–Ganzi terrane.
The Kohistan arc terrane in northern Pakistan preserves one of the most complete intra-oceanic arc sections in the Tethyan orogenic belt; however, the petrogenesis and magmatic fertility characteristics of Early Cretaceous magmatic rocks in the northwestern Kohistan Batholith remain poorly constrained. Here, we investigate the Mirkhani diorite–granodiorite intrusion and the associated basaltic andesite rocks using an integrated dataset comprising zircon and apatite U–Pb geochronology, whole-rock major- and trace-element geochemistry, mineral chemistry, whole-rock Sr–Nd–Pb isotopes, zircon Lu–Hf isotopes, and apatite Sr–Nd isotopes. Zircon U–Pb dating constrains the emplacement of the intrusion to 110.8 ± 1.5 Ma, whereas apatite U–Pb dating of the basaltic andesite yields 115.6 ± 9.3 Ma; these ages overlap within uncertainty and indicate an Early Cretaceous magmatic episode. Positive whole-rock εNd(t) and zircon εHf(t) values, low initial 87Sr/86Sr ratios, and positive apatite εNd(t) values, together with predominantly lower/depleted 87Sr/86Sr compositions, indicate derivation from a juvenile, subduction-modified mantle source with possible minor crustal assimilation. The basaltic andesite is compositionally more mafic, whereas the Mirkhani intrusion represents a more evolved melt affected by fractional crystallization and minor crustal interaction during its ascent. The enrichment of LILE elements and depletion of Nb–Ta further indicates a mantle wedge modified by slab-derived melts and fluids. Zircon and apatite compositions of the Mirkhani intrusion support hydrous, moderately oxidized magmatic conditions that were favorable for retaining and transporting Cu, although the timing, metal endowment, and direct genetic link of associated and nearby mineralization remain to be established. The Mirkhani magmatism therefore records a sulfide-bearing Early Cretaceous arc-magmatic event and provides new constraints on magmatic arc evolution and mineral exploration in the northwestern Kohistan Batholith.
Southern Central Papua (SCP) is a tectonically active frontier region where complex fold-and-thrust deformation controls hydrocarbon prospectivity and geological hazard potential. Limited subsurface constraints have created uncertainties regarding structural segmentation, migration pathways, and fault-related risks. This study develops an integrated structural reconciliation framework by combining Passive Seismic Tomography (PST), gravity anomaly analysis, geological and borehole constraints, and seismicity distribution to evaluate the relationship between crustal architecture, hydrocarbon potential, and tectonic hazards.The study uses passive seismic data from 85 broadband stations recorded over five months, gravity data processed using Second Vertical Derivative (SVD), tilt derivative, and total horizontal gradient analysis, together with borehole and seismicity information. The integrated interpretation identifies three major structural domains within SCP: the North, Middle, and East Blocks, controlled by major fault systems including the Tarera-Takamani-Aiduna Fault Zone (TTAFZ). Transpressional deformation, flower structures, and stratigraphic repetition are recognized as key controls on reservoir compartmentalization and structural trap development.First-order volumetric screening indicates geological lead volumes of approximately 4.506 km3 at the Top Woniwogi level, around 2 km depth, and 4.654 km3 at the Top Modio level, around 5 km depth. These values represent preliminary geological lead estimates, not definitive resource calculations. More than 800 recorded seismic events indicate ongoing tectonic activity, showing that exploration opportunities coexist with fault-related geological risks.
Episodic intraplate deformation far from active plate margins remains poorly understood, particularly in long-lived convergent systems. Here we integrate calcite U–Pb geochronology and REE geochemistry of fault-related veins with regional tectonic constraints to reveal punctuated brittle deformation across the South China Block (SCB) from the Late Jurassic to the Cenozoic. A total of fourteen calcite vein samples were analyzed. The obtained U–Pb ages are ∼147 ± 4, 139 ± 4, 114 ± 16, 91 ± 8, 83 ± 6, 70 ± 2, 60 ± 2, and 50 ± 3 Ma, with younger activation at ∼45 ± 3 Ma, recording episodic fault activity at intervals of ∼10 Ma over more than 100 Myr within the western SCB. The ca. 147–91 Ma samples record strike-slip deformation, the ca. 70–60 Ma samples show compressional features, and the ca. 50–45 Ma samples exhibit extensional characteristics. The calcite samples show consistent enrichment in light REEs (LREEs), with total REE concentrations ranging from 0.1 to 36.6 ppm. REE ratios suggest that the vein-forming fluids were derived from mixing between tectonically driven thermal fluids and meteoric hydrothermal systems. Notably, these faulting episodes do not exhibit any systematic progressive trend either toward the continental interior or toward the coast. We propose that this punctuated intraplate deformation was likely triggered by the steepening and rollback of the subducting Paleo-Pacific slab, which in turn induced lithospheric thinning and a seesaw-like tectonic adjustment of the SCB since the Late Jurassic.
The Ediacaran represents a significant period in the Earth’s history, and sedimentary manganese deposits precipitated in the late Ediacaran, which were hosted in the black shales of the upper Doushantuo Formation. However, their depositional redox conditions and the processes of Mn carbonate formation remain controversial. This study combines statistical analysis of framboidal pyrite size distributions with random forest (RF) classification to reconstruct paleo-redox conditions using 14 samples from drill core ZK-01 in the Gaoyan manganese deposit. A total of 1517 framboids were measured. Diameters were mainly 4–10 μm, with a mean of 6.68 μm, and 89.39 % were smaller than 10 μm. The RF classifier was trained on size statistics from 130 samples compiled from published studies and achieved a test accuracy of 84.6 % for the reference redox classes. Ten studied samples were assigned to the anoxic-dominated reference class and four to the oxic–dysoxic reference class. The framboidal pyrite size distributions and RF classification indicate predominantly anoxic deep water, with intermittent shifts toward more oxic conditions during Mn deposition. Together with previously reported mineralogical and Tl isotope evidence, these paleo-redox results support a two-stage metallogenic model involving Mn oxide precipitation, reductive dissolution, and subsequent Mn carbonate formation. The RF approach complements traditional framboidal pyrite size analysis and provides additional constraints on depositional redox conditions.
