Search Results (15)

The Altyn Tagh Fault plays a critical role in understanding the tectonic evolution of the northern margin of the Tibetan Plateau. However, considerable debate persists regarding its activity and deformation history. This study investigates volcanic rocks from the Beidayao-Jianquanzi-Hanxia-Hongliuxia area in the eastern segment of the fault. By employing zircon U-Pb dating, whole-rock geochemistry, and Sr-Nd isotope analysis, we aim to elucidate their petrogenesis and tectonic setting, thereby providing new insights into the crustal evolution of the eastern Altyn Tagh Fault. Zircon U-Pb dating of the Hongliuxia rhyolite yields a weighted mean ²⁰⁶Pb/²³⁸U age of 106.6 ± 0.6 Ma, indicating an Early Cretaceous eruption. Geochemically, the western part of the study area (Beidayao and Jianquanzi) is dominated by basalts that exhibit significant enrichment in large ion lithophile elements and light rare earth elements, together with high Nb concentrations (>20 ppm), as well as high Nb/La (0.64–1.12) and Nb/U (29.8–35.42) ratios, consistent with the characteristics of high-Nb basalt. In contrast, the eastern area (Hanxia and Hongliuxia) is characterized by andesitic rocks that display typical continental arc affinities, marked by enrichment in Th, U, and Pb and depletion in Nb, Ta, and Ti. Isotopically, the basalts show initial ⁸⁷Sr/⁸⁶Sr ratios of 0.706–0.707 and ε_Nd (t) values ranging from −3.2 to 0.8, whereas the andesites possess more radiogenic Sr isotopic compositions, with (⁸⁷Sr/⁸⁶Sr)_i ratios of 0.710–0.717, and more negative ε_Nd (t) values from −11.4 to −1.5, suggesting derivation from an enriched mantle source. Integrating geochemical data with regional geological records, we propose that the eastern part of the Altyn Fault experienced a significant intracontinental extensional setting during the Early Cretaceous, where asthenospheric mantle upwelling played a key role in the generation of the volcanic rocks. This study provides key petrological and geochemical constraints on Early Cretaceous deformation and activity along the Altyn Tagh Fault, and also offers a valuable reference for understanding the evolution of similar fault systems. Full article

To further investigate the collision process and tectonic regime transition between the North China (NCB) and South China Block (SCB), two magnetotelluric profiles were arranged across the Dabie Orogeny Belt (DOB) and eastern SCB. We then obtain the lithospheric resistivity models. The prominent feature revealed by our new model is an extensive conductive arc from the lower crust to the upper mantle, across the Jiangnan orogenic belt (JNOB) and the eastern Cathaysia Block (CAB). In addition, a huge resistor beneath the conductive arc is revealed, which is separated by a conductive wedge. Combining the heat flow and seismic tomographic imaging results, the conductors are to contain a large amount of hot material that present as the detachment layers (belts) controlled by the two subduction slabs. Considering multi-phase magmatism in the study area, new models suggest an intracontinental tectonic event in eastern CAB. Therefore, we propose a reliable tectonic process that occurred in the study area, including five stages: (1) an eastward intracontinental subduction and orogen carried out in CAB before the collision between SCB and NCB; (2) an extensional structural developed in CAB, following the subduction slab wrecking/sinking; (3) after the collision with NCB, the SCB crust/lithosphere thickened following the westward subduction of the Paleo-Pacific plate; (4) following the westward Yangtze slab sinking, the regional extension developed with the asthenosphere upwelling beneath SCB; (5) afterwards, the SCB was welded into one continent in a setting of westward compression. Full article

The Ouarzazate Group in the Anti-Atlas Belt of southern Morocco, part of the West African Craton (WAC), is a significant Proterozoic lithostratigraphic unit formed during the late Ediacaran period. It includes extensive volcanic rocks associated with the early stages of Iapetus Ocean opening. Zircon U-Pb dating and geochemical analyses of the Oued Dar’a Caldera (ODC) volcanic succession in the Saghro Massif reveal two major eruptive cycles corresponding to the lower and upper Ouarzazate Group. The 1st cycle (588–563 Ma) includes pre- and syn-caldera volcanic succession characterized by basaltic andesite to rhyolitic rocks, formed in a volcanic arc setting through lithospheric mantle-derived mafic magmatism and crustal melting. A major caldera-forming eruption occurred approximately 571–562 Ma, with associated rhyolitic dyke swarms indicating a larger caldera extent than previously known. The 2nd cycle (561–543 Ma) features post-caldera bimodal volcanism, with tholeiitic basalts and intraplate felsic magmas, signaling a shift to continental flood basalts and silicic volcanic systems. The entire volcanic activity spans approximately 23–40 million years. This succession is linked to late Ediacaran intracontinental super-eruptions tied to orogenic collapse and continental extension, likely in association with the Central Iapetus Magmatic Province (CIMP), marking a significant transition in the geodynamic evolution of the WAC. Full article

The Beishan Orogenic Belt, situated along the southern margin of the Central Asian Orogenic Belt, represents a critical tectonic domain that archives the prolonged subduction–accretion processes and Paleo-Asian Ocean closure from the Early Paleozoic to the Mesozoic. Early Permian magmatism, exhibiting the most extensive spatial-temporal distribution in this belt, remains controversial in its geodynamic context: whether it formed in a persistent subduction regime or was associated with mantle plume activity or post-collisional extension within a rift setting. This study presents an integrated analysis of petrology, zircon U-Pb geochronology, in situ Hf isotopes, and whole-rock geochemistry of Early Permian granites from the Tiancang area in the southern Beishan Orogenic Belt, complemented by regional comparative studies. Tiancang granites comprise biotite monzogranite, monzogranite, and syenogranite. Zircon U-Pb dating of four samples yields crystallization ages of 279.3–274.1 Ma. These granites are classified as high-K calc-alkaline to calc-alkaline, metaluminous to weakly peraluminous I-type granites. Geochemical signatures reveal the following: (1) low total rare earth element (REE) concentrations with light REE enrichment ((La/Yb)_N = 3.26–11.39); (2) pronounced negative Eu anomalies (Eu/Eu* = 0.47–0.71) and subordinate Ce anomalies; (3) enrichment in large-ion lithophile elements (LILEs: Rb, Th, U, K) coupled with depletion in high-field-strength elements (HFSEs: Nb, Ta, P, Zr, Ti); (4) zircon ε_Hf(t) values ranging from −10.5 to −0.1, corresponding to Hf crustal model ages (T_DMC) of 1.96–1.30 Ga. These features collectively indicate that the Tiancang granites originated predominantly from partial melting of Paleoproterozoic–Mesoproterozoic crustal sources with variable mantle contributions, followed by extensive fractional crystallization. Regional correlations demonstrate near-synchronous magmatic activity across the southern/northern Beishan and eastern Tianshan Orogenic belts. The widespread Permian granitoids, combined with post-collisional magmatic suites and rift-related stratigraphic sequences, provide compelling evidence for a continental rift setting in the southern Beishan during the Early Permian. This tectonic regime transition likely began with lithospheric delamination after the Late Carboniferous–Early Permian collisional orogeny, which triggered asthenospheric upwelling and crustal thinning. These processes ultimately led to the terminal closure of the Paleo-Asian Ocean’s southern branch, followed by intracontinental evolution. Full article

The South China Plate is an important part of the Rodinia supercontinent in the Neoproterozoic. The Rizhao area, located on the northeastern margin of the South China Plate, records multiple periods of magmatism, among which Neoproterozoic granitic gneiss is of great significance to the tectonic evolution of the South China Block. In this study, systematic petrology, geochemistry, isotopic chronology, and zircon Hf isotopic analyses were carried out on gneisses samples of biotite alkali feldspar granitic and biotite monzogranitic compositions in the Rizhao area. Geochemical analyses suggest that these granitic rocks belong to the sub-alkaline series and have high potassium contents. They are enriched in large-ion lithophile elements K, Rb, and Ba; depleted in high field strength elements P, Nb, and Ti; enriched in light rare earth elements and moderately depleted in heavy rare earth elements; and have weak to moderate negative Eu anomalies and weak negative Ce anomalies. These rocks are post-orogenic A-type granites. LA-MC-ICP-MS U-Pb dating of zircons from two biotite alkali-feldspar granitic gneiss samples yielded weighted mean ages of 785 ± 8 Ma (MSWD = 3.0) and 784 ± 6Ma (MSWD = 1.5), respectively, and a biotite monzogranitic gneiss sample yielded a weighted mean age of 789 ± 6 Ma (MSWD = 2.3). Lu-Hf isotopic analyses on zircon grains from the two types of Neoproterozoic-aged gneisses yielded negative ε_Hf(t) values ranging from −19.3 to −8.8 and from −18.3 to −10.4, respectively, and the corresponding two-stage Hf model age ranges are 2848–3776 Ma and 2983–3682 Ma, respectively. These granites are the product of Neoproterozoic magmatic activity and are mainly derived from the partial melting of Archean continental crust. Combining the geochemical characteristics and zircon U-Pb-Lu-Hf isotopic analyses, these A-type granitic gneisses appear to have formed in an intracontinental rift extension environment during the initial break-up of the Rodinia supercontinent, as part of the supercontinent break-up process at the northeastern margin of the South China Block. Full article

The Helanshan Mountain tectonic belt (HTB) is an intraplate deformation belt along the northwestern border of the Ordos Block in the North China Craton. When and why this intracontinental tectonic belt formed, its subsequent uplift and erosion, and the relationships between ranges and adjacent basins remain unclear. To better assess the connections between the temporal and structural activity in HTB, apatite fission-track (AFT) and zircon fission-track (ZFT) analyses were conducted in this study. The lack of adequate FT data from the HTB is a source of contention and dispute. This paper collected samples for AFT and ZFT techniques from the central and southern HTB, trying to improve the research. The ZFT and AFT ages could be divided into the following 7 groups: 279 Ma, 222–213 Ma, 193–169 Ma, 151–147 Ma, 130–109 Ma, 92–77 Ma, and 65–50 Ma. The inverse modeling results of AFT indicate 4 fast cooling episodes of 170–120 Ma, 120–95 Ma, 66–60 Ma, and ~10–8 Ma to the present. Combining the results of FT analysis with radial plot and inverse modeling of AFT, the following eight age groups are believed to reveal the distinct tectonic activities in HTB: the first age group of 279 Ma mainly represented the back-arc extension of the southern HTB; the age group of 222–213 Ma was bounded with NNE-SSE trending contraction between the South China block and North China Craton; the event of 193–169 Ma responded to the post-orogenic collapse followed after the second event; the 151–147 Ma group was interpreted as the eastward extrusion induced by the subduction between Qiangtang and Lhasa blocks; the Early Cretaceous (130–109 Ma) group was not only affected by the rollback of the Pacific Plate, but also denoted the collapse of the thickened lithosphere formed in the Late Jurassic; the Late Cretaceous (92–77 Ma) group was attributed to long-distance impact from the subduction of the Pacific Plate beneath the Eurasian Plate; the event during 65–50 Ma was a correspondence to far-field effect of the onset collision between the Eurasian and Indian Plates; and from 10–8 Ma to the present, the progressive collision of the Indian and Eurasian Plates have a significant impact on the HTB and the northeastern Tibetan Plateau. Full article

The Huayangchuan U-polymetallic deposit in the Qinling Orogen is a newly verified carbonatite-hosted deposit on the southern margin of the North China Craton (NCC) in Central China. Granitic magmatism is extensively developed in the Huayangchuan deposit area and is lacking analysis on the reasons for these situations; however, its ages, petrogenesis, and relationship with uranium mineralization are not well constrained. Zircon U–Pb ages for the hornblende-bearing granite porphyry and medium-fine-grained biotite granites in close proximity to carbonatite rocks are 229.8 ± 1.1 and 135.3 ± 0.6 Ma, respectively. High-K calc-alkaline series and weakly peraluminous Triassic hornblende-bearing granite porphyry are slightly enriched in light rare earth elements (LREE) with flat heavy rare earth element (HREE) patterns, enriched in Ba and Sr, and depleted in Nb, Ta, P, and Ti, i.e., geochemical characteristics similar to those of adakite-like rocks. The Early Cretaceous medium-fine-grained biotite granites are characterized by LREE enrichment and flat HREE patterns, which belong to high-K calc-alkaline series, and metaluminous belong to weakly peraluminous I-type granite, with U and large ion lithophile element (LILE) enrichment and high field strength element depletion. The high initial ⁸⁷Sr/⁸⁶Sr ratios and enriched Nd (ε_Nd(t) = −10.7 to −9.5 and −19.9 to −18.9, respectively) and Hf (ε_Hf(t) = −21.8 to −13.0 and −30.5 to −19.0, respectively) isotopes revealed that both granitic rocks from the Huayangchuan deposit mainly originated from lower crustal materials, generated by partial melting of the ancient basement materials of the Taihua Group. Triassic hornblende-bearing granite porphyry is significantly different from the mantle origin of the contemporaneous U-mineralization carbonatite. In combination with tectonic evolution, we argue that the Qinling Orogenic Belt was affected by the subduction of the North Mianlian Ocean during the Late Triassic. The ongoing northward subduction of the Yangtze Craton resulted in crustal thickening, forming large-scale Indosinian carbonatites, U-polymetallic mineralization, and contemporaneous intermediate-acid magmatism. Additionally, due to the tectonic system transformation caused by Paleo-Pacific Plate subduction, intracontinental lithosphere extension and lithospheric thinning occurred along the southern NCC margin in the Early Cretaceous. Intense magma underplating of the post-orogeny created a large number of magmatic rocks. The tremendous heat could have provided a thermal source and dynamic mechanism for the Yanshanian large-scale U-polymetallic mineralization events. Full article

The Late Paleozoic tectonic evolution of the Xing’an block in the eastern Central Asian orogenic belt has long been the subject of debate. In this paper, a comprehensive study of U-Pb zircon ages, Lu-Hf isotopes and whole-rock elemental analyses was carried out on Hadayang schists. Representative samples of the epidote-biotite-albite schist and biotite-albite schist yielded the weighted mean ²⁰⁶Pb/²³⁸U ages of 360 ± 2 Ma and 355 ± 3 Ma, respectively. This indicated the presence of Late Devonian–Early Carboniferous intermediate-basic rocks in the eastern Xing’an block. The Hadayang schists exhibited a Na-rich, tholeiitic and calc-alkaline affinity in composition with low Mg# (35.2–53.0), Cr (23.7–86.5 ppm), Ni (21.1–40.0 ppm) and Co (12.1–30.6 ppm). They were characterized by enrichment of LILEs, depletion of HFSEs and highly positive zircon ε_Hf(t) values (the average values were +8.93 and +9.29, respectively). The magma source of the Hadayang schists was a mantle that consisted of both spinel and garnet lherzolite, with a partial melting degree of 1%–5%, and it had undergone fractional crystallization of olivine, orthopyroxene and plagioclase. The Hadayang schists, together with other Late Devonian–Early Carboniferous intermediate-basic magmatic rocks in the eastern Xing’an block, were formed in an intracontinental extension tectonic setting similar to that of the North American Basin and Range basalt. Moreover, Late Devonian–Early Carboniferous ophiolite under a similar tectonic background in the western Xing’an block has been reported. We believe that the Xing’an block would have been in the stage of intracontinental extension during the Late Devonian–Early Carboniferous. Full article

The Yangshan gold belt is renowned for its igneous rock formations, particularly dykes that form in tectonically weak zones. Some of these rock formations exhibit a close spatial relationship with gold mineralization, and a tiny portion of the granitic dykes serve as gold ore bodies by themselves. In order to investigate the nature of granitic dykes and their association with gold mineralization, we conducted a comprehensive study consisting of zircon U-Pb chronology, petrography, and in situ Hf isotope analysis of 25 granitic dyke samples collected from east to west across the belt. According to LA-ICP-MS zircon U-Pb dating results, the granitic dykes inherited zircon ages that are concentrated between 745.0 and 802.0 Ma, and magmatic intrusion ages that mainly fall between 201.0 and 213 Ma. Moreover, the granitic dykes display a calc-alkaline to high-K calc-alkaline peraluminous series, which is relatively enriched in light over heavy REE, with moderate Eu anomalies. These dykes are rich in large-ion lithophile elements and poor in high-field-strength elements. The zircon Lu-Hf isotope data range from εHf(t) values of −1.5 to 0.1, mantle model (T_DM¹) ages range from 859 to 937 Ma, and crustal model (T_DM²) ages range from 1111 to 1218 Ma. The granitic dykes found in the Yangshan gold belt were formed between 200 and 213 Ma ago, during a period of intracontinental extension following the late collision between the Yangtze plate and Qinling microplates. These dykes originated from the volcanic basement of the Mesoproterozoic Bikou Group, which was formed by the melting of the upper crust under the crustal thickening caused by the subduction and collision of the Qinling microplate. Subsequently, the dykes were transported along a tectonically weak zone, assimilating surrounding rocks and undergoing a transformation from “I”-type to “S”-type granite before finally evolving into granite with specific “A”-type characteristics. Our study provides new insights into the petrogenesis of granitic dykes in the Yangshan gold belt, as well as the relationship between gold mineralization and magmatic activity, which has significant implications for mineral exploration and the geological understanding of gold mineralization in this region. Full article

The Bogda Range (hereafter referred to as the Bogda) is located in the Eastern Tianshan. Interpreting its tectono-thermal history is critical to understanding the intra-continental evolution of the Tianshan. In this study, we report new apatite fission track data from the late Paleozoic–Mesozoic sedimentary rocks in the northern Bogda and the Late Paleozoic granites in the southern Bogda to investigate the exhumation history of the Bogda. Apatite fission track ages dominantly range from the Jurassic to earliest Cenozoic (~143–61 Ma), except for one siliciclastic sample from the Early Permian strata with an older age of ~251 Ma. Thermal history modeling, together with detrital apatite fission track age peaks, reveal that the Bogda underwent three episodes of cooling during the Late Triassic, the Late Cretaceous, and the Late Miocene. The Late Triassic rapid cooling may represent the initial building of the Bogda, which is probably related to the final closure of the Paleo-Asian Ocean. During the Late Cretaceous, the Bogda may have experienced a moderate exhumation, which was possibly triggered by the extensive tectonic extension in the central–eastern Asian regime during the Cretaceous. The Late Miocene rapid cooling may be a response to the rapid uplift of the whole Tianshan, due to the far-field effect of the continuous India–Eurasia collision since the beginning of the Cenozoic. Full article

In this study, ⁴⁰Ar/³⁹Ar geochronology and major and trace element data were presented for Paleogene basaltic rocks from the Jiangling Basin, China. The volcanic rocks erupted at ca. 53.19–60.78 Ma and belonged to the sub alkaline series. These basaltic rocks are generally characterized by enrichment in large-ion lithophile elements (LILEs) and light rare earth elements (LREEs) ((La/Yb)_cn = 6.14–11.72) and lack of Eu anomalies (Eu/Eu* = 0.98–1.09), similar to ocean island basalts. The geochemical signatures of these rocks are similar to hotspot-related Paleogene volcanic rocks in the North China Block and late Cenozoic volcanic rocks in Southeast China. The Cenozoic lithospheric mantle, as well as the Mesozoic basalts that are beneath the northern Yangtze Blocks, might be inherited from the Mesozoic lithospheric mantle. The basaltic rocks from the Jiangling Basin in the northern Yangtze Block were generated from the partial melting of EMII (enrichedmantleII)-like lithospheric mantle due to the intracontinental extension. Full article

The final closure time of the Paleo-Asian Ocean and the Permo-Carboniferous tectonic settings in the northern Alxa are very important but controversial tectonic issues. The geochronology and petrogenesis of mafic igneous rocks are superior in clarifying regional tectonic settings. Here, we report on zircon U-Pb-Hf isotopes, biotite ⁴⁰Ar/³⁹Ar geochronology and whole-rock geochemical data of the hornblende gabbro from the Baogeqi gabbro pluton in the northern Alxa. The LA-ICP MS U-Pb analysis of zircon grains from the hornblende gabbro yield a weighted mean age of 262.7 ± 2.3 Ma (2σ, MSWD = 0.74), manifesting that the Baogeqi gabbro pluton emplacement was during the late Middle Permian (Capitanian). The ⁴⁰Ar/³⁹Ar dating of biotite grains from the hornblende gabbro yields a plateau age of 231.3 ± 1.6 Ma (2σ, MSWD = 0.55), indicating that the Baogeqi gabbro pluton cooled to below 300 ℃ in the Triassic. The hornblende gabbro samples are calc-alkaline with metaluminous character, and show enrichment in large ion lithophile elements (e.g., Rb, Ba, Sr, and K) but depletion in Nb, Ta, P, Th, and Ti relative to primitive mantle. Combined with the positive zircon εHf(t) values (+4.9–+9.4), we suggest that the magmas formed from the partial melting of depleted mantle were metasomatized by slab-derived fluids. Together with regional geology, these geochemical data suggest that the Baogeqi gabbro pluton was formed in an intracontinental extension setting, further indicating that the Paleo-Asian Ocean in the northern Alxa was closed prior to the late Middle Permian (Capitanian), and this region was in a post-collision extensional setting during the Capitanian-Late Permian. In addition, the Triassic cooling of the gabbro pluton may be a record of the decline of the Capitanian-Late Permian post-collisional extension basin due to the far-field effect of subduction-collision during the closure of the Paleo-Tethys Ocean. Full article

The Chaiwopu Depression in the southern Junggar Basin is located between the West Bogda Mountains and the northeastern Tian Shan Mountains in northwest China. The intracontinental basin–mountain system was formed in the Central Asian Orogenic Belt during the Late Paleozoic. The Permian strata around the depression exhibits distinct variations, which provide significant information to understand its tectonic and depositional evolution. This study investigated six outcrop sites using lithological, sedimentological, and geochemical analyses. The representative lithology of the Lower Permian is submarine lava and pyroclastic flows on the northern margins and alluvial deposits near the southern margins. In the Middle Permian sequence, the extensive distribution of alternating shale and silt/sandstone with oil shale and carbonate indicates a lacustrine setting. The sediments are composed of felsic rock-forming minerals derived mainly from island arc settings. The source rock properties correspond to the Carboniferous volcanic terrain of northeastern Tian Shan. The Lower to Middle Permian source-to-sink system occurred in an incipient level of weathering and maturation, a simple recycling process, and arid to semi-arid climatic conditions. The characteristics and changes of the depositional environment and provenance can be understood in terms of implications of tectono-paleogeographic evolution associated with the West Bogda rifting and uplift. Full article

Cenozoic alkali basalts in Southeast (SE) China generally are genetically related to intracontinental rifting. Hence, they can be used to probe the nature of their underlying mantle sources and aid studies of the tectonic background in this region. This paper focuses on the Shanhoujian alkali basalts located in Bailing County, northeastern Fujian, SE China. We herein report their petrology, whole-rock major, and trace element geochemistry, and Sr-Nd isotopic composition and provide a new zircon U-Pb age for the basalts (~40 Ma, Eocene). These data help to constrain the petrogenesis of alkali basalts, their mantle source, and tectonic settings. The basalts are characterized by high Mg^# (58.21–63.52) with Na₂O/K₂O > 1. MgO content is weakly correlated with CaO and Cr content but shows no correlation with Ni and Fe₂O₃ (total). Such features suggest that fractionation of clinopyroxene rather than olivine was important. In terms of trace elements, the alkali basalts display: (1) enrichment in La, Ce, Rb, Ba, Nb, and Ta and depletion in K, Pb, Zr, Hf, and Ti and (2) notable fractionation of light rare earth elements from heavy rare earth elements. Determined (⁸⁷Sr/⁸⁶Sr)_i is in the range of 0.7041–0.7040 and ε_Nd (t) is between +3.2 and +3.3. The Shanhoujian alkali basalts show a notable affinity to oceanic island basalts (OIBs) with little assimilation of crustal materials. They were derived from a pyroxenite and carbonated peridotite mantle source metasomatized by sediments carried by the subduction plate at different depths. The primary magmas of these basalts were derived from partial melting of this metasomatized mantle source during upwelling of the asthenospheric mantle as an intracontinental rift formed through extension in this part of SE China. Full article

A suite of mafic intrusions, composed of diabase and micro-gabbro outcrops in the Jingxi area of southern Youjiang Basin, SW China. This study conducts geochronological, geochemical, and Sr–Nd isotopic analyses on the mafic intrusions in Jingxi with the aim of determining their petrogenesis, tectonic setting, and metallogenic implications. Zircon U–Pb dating for the mafic intrusions yielded an age of 183 ± 3 Ma (MSWD = 2.3), which is coeval with the Carlin-like gold mineralization in the Youjiang Basin. The mafic intrusions are alkaline in composition and characterized by low TiO₂ (1.25–1.87 wt %) contents and low Ti/Y ratios (410–550). They exhibit OIB-like patterns of trace element distribution and they have low (⁸⁷Sr/⁸⁶Sr)_i ratios of 0.704341 to 0.705677, slightly negative ε_Nd(t) values of −0.30 to −2.16, low La/Ta (11.57–15.66) and La/Nb (0.77–1.06) ratios, with [La/Yb]_N = 6.52–10.63. The geochemical characteristics, combined with regional considerations, suggest that the mafic intrusions originated from partial melting of upwelling asthenosphere within the garnet-spinel transition zone, as a result of intracontinental back-arc extension triggered by the steep subduction of the Paleo-Pacific plate beneath the South China Block. Moreover, the new data not only suggest Early Jurassic magma was a possible heat source, but also support a magmatism-related model for the Carlin-like gold mineralization in the Youjiang Basin. Full article