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The geodynamic mechanisms that controlled magmatic activity in South China during the late Mesozoic have been a cutting-edge focus of recent research. Southeastern Guangxi, which is located at the juncture between the Pacific and Neo-Tethyan tectonic domains, is a transitional zone characterized by the occurrence of widespread Jurassic–Cretaceous magmatic rocks. Investigation of this region can shed light on the late Mesozoic tectonic setting of South China. We conducted U–Pb geochronological and geochemical analyses of the Liuwang granodiorite and quartz porphyry, which are exposed in southeastern Guangxi. Zircon U–Pb dating yielded an age of 161.8 ± 1.2 Ma for the granodiorite and 97.89 ± 0.68 Ma for the quartz porphyry, indicating that they formed during the Late Jurassic and Late Cretaceous, respectively. The Liuwang granodiorites are weakly peraluminous high-K calc-alkaline rocks characterized by enrichment in large ion lithophile elements (including Rb) and high field strength elements (including Th, U, Pb, and Ta) and depletion in Ba, Nb, and Sr. The granodiorites also exhibit weak rare earth element (REE) fractionation and slightly negative Eu anomalies. Conversely, the Liuwang quartz porphyry is weakly peraluminous and belongs to the potassic syenite series, transitioning into the high-K calc-alkaline series. It is characterized by enrichment in Rb and high field strength elements (including Th, U, Pb, and Ta), with depletion in Ba, Nb, Sr, and Zr. It does not exhibit REE fractionation but does yield prominent negative Eu anomalies. The granodiorite and quartz porphyry yield εHf(t) values of −23.26 to −2.48 and −4.4 to +0.8, respectively, with tDM2 ages of 2642–1270 and 1411–1081 Ma, respectively. These data suggest that the Liuwang granodiorite formed under a background of Late Jurassic lithospheric extension–thinning and was derived from partial melting of Palaeoproterozoic–Mesoproterozoic metasedimentary sandstones with a minor contribution from mantle-derived melts. In contrast, the Liuwang quartz porphyry was derived from partial melting of Mesoproterozoic pelitic rocks and formed in a Late Cretaceous tectonic setting linked to the northward subduction of the Neo-Tethys Ocean beneath South China. [ABSTRACT FROM AUTHOR]

Garnet is the most common alteration mineral in skarn-type deposits, and the geochronological research on it can limit the mineralization age. The Longwan Pb–Zn deposit, situated within the Fozichong Pb–Zn ore field in Guangxi, lacks precise geochronological data, limiting the in-depth comprehension of its genesis and tectonic setting. This study employs LA-ICP-MS U–Pb dating of garnets developed in the skarn orebody and zircons in the associated granitic porphyry to determine the deposit's mineralization age. Backscatter electron images and electron probe microanalysis reveal common zonation characteristics in garnets from the Longwan Pb–Zn deposit, with dominant end-member compositions of Andradite and Grossular. The values of U concentrations range from 1.8 ppm to 3.7 ppm, and a garnet U–Pb age of 102.6 ± 1.9 Ma was obtained, consistent with the zircon U–Pb age of 102.1 ± 1.2 Ma from the granite porphyry within the deposit. The Longwan Pb–Zn deposit formed during the late Early Cretaceous as a skarn deposit resulting from contact metasomatism between the granite porphyry and the host rock. The deposit likely formed in response to the Neo-Tethys plate subducting beneath the South China continent during the Cretaceous, followed by a retreat during the Late Cretaceous. The Cenxi-Bobai Fault experienced reactivation under the extensional tectonic regime induced by the Neo-Tethys Ocean's retreat, leading to a series of magmatic activities along the NE-trending direction within the Fault. The Longwan Pb–Zn deposit formed during the processes of magma emplacement and contact metasomatic reactions with the country rock. [ABSTRACT FROM AUTHOR]

Antimony deposits contain little Sn, whereas Sb and Pb are not the principally contained metal of granite-related Sn deposits. The Danchi Sn-metallogenic ore belt (DSOB) in southwestern China is characterized by Sn-Sb-Zn-Pb co-enrichment, yet the triggers are poorly constrained. The Beixiang deposit in the southern DSOB consists of stage I Sn-Zn and stage II Sb-Pb-Zn mineralization. Here, we analyzed the cassiterite U-Pb age, fluid inclusion H-O and sulfide Pb-S isotopes, and calcite trace elements of the Beixiang ores. By comparing with the Dachang and Mangchang Sn-polymetallic ore-fields within the DSOB, we constrained the timing of regional mineralization and revealed the processes causing the Sb-Pb co-enrichment. The cassiterite U-Pb dating yielded 90.6 ± 4.5 Ma (MSWD = 2.6), similar to the ages of the Dachang and Mangchang ore fields, indicating the Late Cretaceous mineralization event throughout the DSOB. The fluid inclusions from stage II ore have δ18OH2O (−2.8 to −7.8‰) and δDV-SMOW (−90.5 to −59.3‰), and the synchronous calcite features have low REE contents, upward-convex REE patterns, and weak Eu anomalies. These suggest that the ore fluids were derived from meteoric water and oil field brine, which dissolved S and Pb from local strata as recorded by sulfide sulfur (δ34SV-CDT = −6.2 to −4.0‰) and Pb isotopes. However, calcite from the stage I ore have higher REE contents and (La/Yb)N, with strong positive Eu anomalies, indicating that the Sn-rich ore fluids were released by greisenization of granite. Overall, we suggest that the combination of granitic magma- and oil field brine-derived fluids, rich in Sn-Zn and Sb-Pb-Zn, respectively, caused the co-enrichment of Sn-Sb-Pb-Zn in Beixiang and throughout the DSOB. [ABSTRACT FROM AUTHOR]

One of the most important geological features of South China are the widespread Mesozoic igneous rocks that play a key role in revealing the tectonic evolution of South China. Due to the thick covering of vegetation and Quaternary sediments, the early Cretaceous magmatism in southwestern South China is still not well constrained. In this paper, we report newly identified early Cretaceous granites in Guangxi, South China. Zircon U–Pb dating results showed that representative fine-grained and coarse-grained granites in northeastern Guangxi indicate the early Cretaceous ages of 141 ± 3 Ma and 141 ± 4 Ma, respectively. Geochemically, both fine-grained and coarse-grained granites had high 10,000 × Ga/Al ratios and belonged to A-type granite. They had undergone high degrees of magma differentiation, as evidenced by extremely negative Sr, Ba, and Eu anomalies. They had high REE (rare earth elements) contents (>451 ppm). The fine-grained granites were characterized by higher HREE (heavy rare earth elements) contents, lower LREE (light rare earth elements) contents, and lower LREE/HREE ratios than the coarse-grained granites. Integrated with regional geological data, the early Cretaceous granites were likely formed in a back-arc extensional environment in response to the increased subduction angle of the Paleo-Pacific plate. Different REE contents in the fine- and coarse-grained granites may be a result of fractional crystallization. Magma differentiation and hydrothermal alteration might have played an important role in REE mineralization of the early Cretaceous granites in Guangxi. [ABSTRACT FROM AUTHOR]

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U–Pb dating and Hf isotopes of detrital zircons from the Nanhua System in Longsheng, northern Guangxi, were investigated to determine the depositional age and provenance of the Nanhua System and the early crustal evolution stages of the South China. U–Pb ages of detrital zircons from the Chang'an Formation of the Nanhua System in Longsheng, northern Guangxi, are mainly 0.66 ~ 0.72 Ga and 0.72 ~ 0.90 Ga, with εHf(t) ranging from −17.05 to 12.79. The dominant provenance is composed of Neoproterozoic magmatic rock from the southeastern margin of the Yangtze Block and the Nanhua period detrital material from Cathaysia Block. U–Pb ages of detrital zircons from the Fulu Formation can be divided into four major groups, that is, 0.64 ~ 0.72 Ga, 0.72 ~ 0.90 Ga, 1.80 ~ 2.20 Ga, and 2.30 ~ 2.80 Ga, with εHf(t) ranging from −27.66 to 11.68. The main provenance is Neoproterozoic magmatic rock from the southeastern margin of Yangtze Block, followed by the Nanhua period detrital material from the Cathaysia Block and geological body equivalent to the assembly of the Columbia Supercontinent. U–Pb age of detrital zircons from Lijiapo Formation is concentrated in 0.72 ~ 0.90 Ga, with εHf(t) ranging from −16.02 to 11.87, and the main provenance comes from Neoproterozoic magmatic rock in the south‐east margin of Yangtze Block. The second‐stage Hf model age (TDM2) of the Nanhua System is 0.84 ~ 4.51 Ga, with two obvious peak intervals of 0.90 ~ 1.30 Ga and 1.40 ~ 2.10 Ga, and two secondary peak intervals of 2.40 ~ 3.00 Ga and 3.10 ~ 3.60 Ga, which can be interpreted that the research area has experienced four stages of crustal growth: 3.10 ~ 3.60 Ga, 2.40 ~ 3.00 Ga, 1.40 ~ 2.10 Ga, and 0.90 ~ 1.30 Ga. The detrital zircon age spectra indicate that the Chang'an Formation and Fulu Formation of the Nanhua System contain more detrital zircons which is contemporaneous with strata due to the Xuefeng orogeny, while the Lijiapo Formation contains a very small amount of detrital zircon which is contemporaneous with strata, suggesting that the tectonic setting has shifted to a passive continental margin or pull‐apart basin during the period of the Lijiapo Formation. [ABSTRACT FROM AUTHOR]

[Display omitted] • The age of Gaolong deposit was defined at 156.8 ± 8.3 Ma for the first time. • Ore-forming materials were leached or derived from the deep continental crust. • Apatite geochemistry was inherited from hydrothermal fluids and governed by complexations. • Fingerprints of hydrothermal apatite in sediment-hosted hydrothermal ore systems. Apatite can record the evolution of magmatic–hydrothermal ore systems, but it is unclear whether it is suitable for investigating low-temperature, sediment-hosted hydrothermal ore systems. To fill the knowledge gap. we investigated the Gaolong Carlin-type Au deposit in the Guangxi Zhuang Autonomous Region, southwestern China (Youjiang Basin). Results show that the hydrothermal apatite occurs in quartz–sulfide ores, has an intact crystal form and homogeneous texture, and is F-rich (2.77–3.67 wt%) and Cl-poor (<0.01 wt%). The apatite is enriched in rare earth elements (REEs; ΣREE = 739–2481 ppm) and has middle-REE-enriched chondrite-normalized REE patterns with positive Eu anomalies (δEu = 1.35–2.00). These REE features were inherited from a reducing hydrothermal system in which anion complexation was dominant. The apatite has high Sr contents (up to 0. 9 wt%) and relatively uniform initial 87Sr/86Sr ratios (0.709055–0.709208), suggesting that Sr was leached or derived from the deep continental crust. In situ U–Pb dating of 156.8 ± 8.3 Ma for apatite shows that the Late Jurassic–Early Cretaceous was an important time for the formation of Carlin-type Au deposits in the Youjiang Basin. The Au mineralization was associated with far-field tectonism and deeply sourced hydrothermal ore-forming fluids. Hydrothermal apatite can be used to fingerprint low-temperature, sediment-hosted hydrothermal ore systems. [ABSTRACT FROM AUTHOR]

[Display omitted] • First report the Paleokarst infilled type orebody in the Danchi Fold-and-Thrust belt, South China. • Pre-ore NE-SW shortening and syn -mineralization E-W extension deformations control the ore distribution. • Zn-, Sn-, and Sb-mineralization have taken place in order in the Wuxu district. • Cassiterites U-Pb dating reveals the tin mineralization in the Wuxu district was formed at 91–90 Ma. • Wuxu district have a great potential for tin mineralization. The Danchi fold-and-thrust belt, Guangxi, South China, contains the Mangchang, Dachang, and Wuxu large and giant Sn-polymetallic districts. It hosts more than 1.2 Mt of ore grading 1 % Sn, 6.23 Mt Zn at 2.4 %, and 1.13 Mt Sb at 1.3 %. Wuxu district is one of the Sb-Zn dominated hydrothermal districts without magmatic rocks exposing in the south of the Danchi belt. Recent drilling and exploring mining have identified a partially Sn mineralization associated with the Zn-Sb mineralization. These works provide an opportunity to evaluate the potential of tin mineralization in the south of Danchi belt and relationship among Sn, Zn, and Sb mineralization. Structural analysis suggests that the Wuxu district underwent at least three deformational phases since the Triassic. The first NE-SW shortening deformation controlled the structural framework of the Wuxu district and is expressed by NW-verging thrusts and folds, axial-plane cleavages around the core of the Wuxu anticline, transverse joint sets on the limbs of the Wuxu anticline, and dilational zones in the bedding-fractures. Afterward, an E-W extension stress field produced NS-striking normal faults and reactivated pre-existing NNW-striking faults which were expressed by sinistral top-to-the north sense of shear. During this deformation, some low order dilational spaces of the NW-striking faults and bedding-fractures formed and a syn -kinematic deposition of minerals in these hosting structures to form the ore shoots. The NNW-striking faults, axial-plane cleavages, and large dilational jogs controlled the subvertical large veins in the Jianzhupo deposit. The conjugate joints and inter-bedding fractures in the limb of the Wuxu anticlinorium controlled the branching veinlets and stratiform, paleokarst infilled ores in the Bawang deposit. The post-ore EW-striking faults are not obvious and displaced preceding two-phase structures and ores. Three primary paragenetic stages of hydrothermal process have been recognized: (I) Sphalerite dominated + massive pyrrhotite with euhedral pyrite porphyroblasts, (II) Cassiterite + siderite + arsenopyrite dominated with minor scheelite + quartz + fluorite, and (III) Jamesonite + stibnite + sulfosalt + carbonates. Cassiterite U-Pb dating provided a lower intercept age of 90.2 ± 3.1 Ma and 90.6 ± 4.6 Ma for the Jianzhupo and Bawang deposits, respectively. These two ages are consistent with the chronological data of tin-sulfides and ore-related felsic intrusions in the Danchi fold-and-thrust belt, South China. Our studies coupled with previous gravity data suggests a distal magmatic-hydrothermal infilling tin-polymetallic district and indicates that the Wuxu district has great potential for additional tin mineralization. [ABSTRACT FROM AUTHOR]

The Bawang deposit, located in the west of Wuxu ore field, southern section of the Nandan-Hechi metallogenic belt, is a medium-sized tin–zinc polymetallic deposit. Its genesis has been a matter of debate because of lacking constraints from isotope geology. In this study, LA-MC-ICP-MS U-Pb dating of cassiterite and C-O-S-Pb isotope analyses of monominerals were used to investigate the mineralization age and source of the ore-forming minerals in the Bawang deposit. LA-ICP-MS U–Pb dating of cassiterite yielded ages of 93.1 ± 4.8 Ma and 85.3 ± 6.3 Ma, indicating that the mineralization occurred in the early Late Cretaceous. The δ13CPDB and δ18OSMOW values of calcites at the ore stage range between −0.41‰ and 0.44‰ (average = −11‰) and between 13.8‰ and 15.40‰ (average = 14.59‰), respectively. This shows that ore fluid sources were a mixture of those derived from magma and stratum. Pyrite and sphalerite have uniform δ34S values (−4.45‰~−2.20‰), indicating that sulfur is also derived from the mixing of magmatic hydrothermal and stratum fluids. The Pb isotopic composition of sulfide (206Pb/204Pb = 18.4055~18.7625, 207Pb/204Pb = 15.6745~15.7209, 208Pb/204Pb = 38.6232~39.0370) is consistent with the granite of the same age, indicating that ore-forming metals are mainly derived from magmatic hydrothermal solution. The Bawang deposit is a hydrothermal vein-type deposit in the external contact zone of Late Cretaceous granite, controlled by tectonic fractures, and formed by the interaction of magmatic hydrothermal fluid and carbonate rock. There may be large skarn-type ore bodies in the deep part. The results of this study provide insights into the research and exploration of similar deposits in Nandan-Hechi metallogenic belt and in the Youjiang Basin. [ABSTRACT FROM AUTHOR]