The Emeishan large igneous province (ELIP) is among the prominent large igneous provinces in the world and has been associated with mantle plume activity. In this study we investigated the impact of the Emeishan mantle plume on generating the sedimentary rock suites of the eastern Sichuan Basin. We present petrology, detrital zircon U – Pb ages, trace elements, and Hf isotopic compositions of the Middle-Late Permian sedimentary sequences in the Huayingshan region to constrain the provenance and characterize the depositional response to the Emeishan mantle plume activity. The detrital zircon U – Pb ages of the Middle Permian Maokou Formation indicate that terrigenous detritus was mainly sourced from the Kangdian paleoland in the southwestern margin of South China. Detrital zircon grains from the bottom of the Late Permian Longtan Formation yield a lower intercept age of 257 ± 28 Ma, interpreted as the contemporaneous metamorphism related to the ELIP magma. The detrital zircon U – Pb ages of the middle part of the Longtan Formation are characterized by unimodal age spectra with a peak at 259 Ma. Provenance analysis indicates that the Longtan Formation was mainly sourced from the Emeishan volcanic rocks in the Huayingshan region. We propose that the Kangdian paleohigh may have been regionally uplifted as the result of the pre-eruption rise of the Emeishan mantle plume in the late Middle Permian. Moreover, this paleohigh was translated into a denuded zone and provided voluminous detritus into the eastern Sichuan Basin. In the early Late Permian, the ELIP magmas upwelled and outpoured from the Huayingshan fault, and flowed past the peripheral rocks to the low terrain in the Huayingshan region. The ELIP volcanic rocks in the Huayingshan region underwent intense post-eruption erosion, resulting in the deposition of voluminous volcanic detritus in the eastern Sichuan Basin.

The hydrothermal dolomitization, facilitated by basement fault activities, had an important impact on the Permian Maokou Formation dolomite in the Sichuan Basin, which experienced complex diagenesis and presented strong reservoir heterogeneity. The source and age of diagenetic fluids in this succession remain controversial. In this study, various analyses were implemented on samples collected from outcrops and wells near the No. 15 fault in the eastern Sichuan Basin to reconstruct the multi-stage fluid activity and analyze the impact on reservoir development, including petrology, micro-domain isotopes, rare earth elements, homogenization temperature of fluid inclusions, and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) U-Pb dating. The homogenization temperature of primary brine inclusions in fine-grained matrix dolomite and saddle dolomite is concentrated between 100 and 150 °C, which indicates that the impacts of abnormally high temperatures of other geological bodies. The δ¹³C and δ¹⁸O value and low ⁸⁷Sr/⁸⁶Sr value indicate that the diagenetic fluid of fine-grained matrix dolomite is mainly Permian seawater. The U-Pb ages of fine-grained matrix dolomite are ~260 Ma, which coincides with the age of the main magmatism of Emeishan Large Igneous Province (ELIP), and hydrothermal fluid provided a favorable high-temperature environment in the penecontemporaneous stage. While highly radiogenic ⁸⁷Sr/⁸⁶Sr compositions suggests those of saddle dolomite, the high-temperature Sr-rich formation fluid. The U-Pb ages of saddle dolomite are 245–250 Ma, which coincides with the age of the 255~251 Ma magmatism of ELIP. This indicates that those should be the diagenetic products of the ELIP hydrothermal fluid in the shallow burial stage. The U-Pb age of coarse-grained calcite is 190–220 Ma, and it should be the diagenetic product of the deep burial stage. Brine inclusions associated with primary methane inclusions were developed in coarse-grained calcite, with a homogenization temperature range of 140.8–199.8 °C, which indicates that the formation fluid activities were related to hydrocarbon charging. The Permian Maokou Formation dolomite was firstly formed in the penecontemporaneous shallow burial stage, and then it was subjected to further hydrothermal dolomitization due to the basement faulting and the abnormally high heat flow during the active period of ELIP. Hydrothermal dolomitization contributed to the formation and maintenance of intercrystalline and dissolution pores, whereas it also formed saddle dolomite to fill the pores, and reduce the pore space. The influence of deep fluid activities on reservoir evolution is further distinguished.

The carbonate rock of the Qiulitage Formation is a significant stratum for oil and gas exploration in the Tarim Basin. To elucidate its environmental characteristics, we conducted tests and analyses of trace elements, carbon, and oxygen isotopes of the carbonate rocks of the Qiulitage Formation in the Kekeqigankake section of the Keping area. The results reveal that δ¹³C values range between −1.7‰ and 4.3‰, with an average value of 1.645‰. δ¹⁸O values fluctuate from −11.4‰ to −6‰, with an average value of −8.2475‰. Z values (paleosalinity) vary from 120.33 to 131.67, significantly exceeding 120 with an average value of 126.52, indicating a marine sedimentary environment. Paleotemperature values (T) range from 12.75 to 29.09 °C, with an average value of 21.36 °C, suggesting warm climate conditions. The Sr/Ba (3.42~24.39) and Sr/Cu (57.5~560) ratios are elevated, while Th/U (<1.32) and V/Cr (0.989~1.70) ratios are reduced, suggesting that the Qiulitage Formation was deposited in an oxygen-rich, warm marine sedimentary environment with relatively high salinity.

Detrital zircons in the matrix of an accretionary complex play an important role in providing evidence to reconstruct oceanic plate subduction and accretion processes. The Nadanhada accretionary complex (NAC) dominated by the Yuejinshan, Raohe and Tongjiang accretionary complexes provides significant geological evidence to better understand the Paleo-Pacific subduction–accretion process. Most previous studies have focused on the Yuejinshan and Raohe accretionary complexes, while those of the Tongjiang accretionary complex on the north side have focused on blocks. In this study, we present zircon U–Pb dating and Hf isotopic data for the matrix of metasedimentary rock in the Tongjiang accretionary complex. The analysis results show that the zircons in the fine silty mudstone, phyllonite and fine argillaceous siltstone define the youngest weighted mean ages (youngest detrital zircon ages) of 261.4 ± 2.9 Ma (247 Ma), 175.2 ± 4.9 Ma (169 Ma) and 168.6 ± 2.1 Ma (162 Ma), respectively, and yield a younging trend of the accretion materials from west to east. Provenance analysis indicates that the matrix was mainly sourced from the neighboring Jiamusi and Xingkai blocks. Based on previous results of the Permian and Late Triassic blocks in the Yuejinshan region, the Permian and Early Jurassic blocks in the Tongjiang region, and the Late Triassic and Early–Middle Jurassic blocks in the Raohe region, as well as the lower limit of the depositional age of the Late Triassic matrix in the Yuejinshan region and the Middle Jurassic and Early Cretaceous matrices in the Raohe region, we propose that the NAC may record the Late Permian–Triassic, Jurassic and Early Cretaceous oceanic accretion events, representing the westward subduction and accretion process of the Paleo–Pacific Ocean Plate.

The closure of the Paleo-Tethys Ocean lead to the collisional amalgamation of the various blocks including South China, Indochina and North China blocks, which results in the formation of the Qinling and Ailaoshan orogenic belts. But the tectonic evolution of the two orogenic belts remains highly debated during the Triassic. The eastern Sichuan Basin, preserving the complete Triassic depositional successions, offers crucial insight into the tectonic evolution of the two orogenic belts in this period. Detailed geological investigations and provenance analyses using detrital zircon U–Pb–Hf isotopic data and trace element compositions are conducted on the Middle Triassic Leikoupo Formation samples in the eastern Sichuan Basin. The age distribution of the middle part of the Leikoupo Formation (Member-2) shows five age clusters of 290∼230 Ma, 330∼290 Ma, 470∼390 Ma, 900∼840 Ma and 1400∼1200 Ma, and those of the top (Member-3) show four age clusters of 250∼238 Ma, 330∼300 Ma, 960∼900 Ma and 2550∼2450 Ma. Considering proximity and widespread distribution, the sediments of the sample at middle part are interpreted to source from the Ailaoshan orogenic belt, the North Qinling orogenic belt and late Paleozoic granites in the Cathaysian Block. The samples at the top primarily originated from the Ailaoshan orogenic belt, basement rocks and Neoproterozoic granites in the Yangtze Block and late Paleozoic granites in the Cathaysian Block. Provenance analysis indicates that the North Qinling orogenic belt can provide a large amount of materials for the Middle Triassic, which suggests this belt was in an uplift stage and was the extension of the Caledonian orogeny since the early Paleozoic. Combining the obtained ages, published data and lithofacies paleogeography, the Early-Middle Triassic source rocks have contributions from the early Mesozoic granites in Ailaoshan orogenic belt, which suggests the Ailaoshan orogenic belt has experienced initial tectonic uplift in the Early Triassic. This initial uplift is related to the collisional amalgamation between the South China Block and Indochina Block.