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Abstract
Lying along the Hegenshan collisional orogenic suture zone in Xi Ujimqin Banner of Inner Mongolia, the Shijiangshan Atype granite intruded into Early Carboniferous Diyanmiao-Baiyinbulage ophiolite as well as Early Permian Shoushangou Formation and Dashizhai Formation, and consists mainly of monzogranites. The granite is geochemically characterized by high SiO2 (74.18%~ 77.16%), K2O (4.31%~5.07%), high absolute alkali values (Na2O+K2O=8.44%~9.16%), low Al2O3, CaO, MgO, TiO2, P2O5, Sr, Ba, Eu, Ti, P values, and higher Ga/Al (3.98~6.09), (Na2O+K2O)/CaO, K2O/MgO, TFeO/MgO, Rb/Nb, Y/Nb, Sc/Nb ratios. It is characterized by typical flat or slight right-inclined gull-wing shaped REE distribution patterns with obvious negative Eu anomalies (δEu=0.01~0.19). The Shijiangshan monzogranite exhibits typical geochemical characteristics of A-type granite, being significantly different from I, S and M type granites in geochemistry. According to the chemical subdivision diagrams of the A-type granitoids, the Shijiangshan A-type granite belongs to aluminous A2-type granitoid, formed and emplaced in a post-orogenic extension setting. LAICPMS zircon U-Pb dating shows that the ages of the granite are 159.8±1.3Ma, 143.1±1.3Ma and 136.20±0.69Ma, suggesting that it was produced during Late Jurassic to Early Cretaceous and that the Hegenshan suture zone was at the post orogenic extension stage in the Late Jurassic-Early Cretaceous period.
... Magmatic activity is very strong in the southern GXR, and acidic magmatic rocks are the main rocks in this region (Figure 1b). Therefore, many researchers have reported different granites in the Haobugao deposit and its surrounding areas, including Daitongshan fine-grained granite (265 ± 5 Ma) [75], Meng'entaolegai biotite granite (250 ± 1 Ma) [34], Baiyinnuoer granodiorite porphyry (171 Ma) [76], Shijiangshan monzogranite (160 ± 1, 143 ± 1 and 136 ± 1 Ma) [77], Shuangjianzishan granite (159 ± 2 Ma) [78], Bengbuleng granodiorite (150 ± 1 Ma) and granite (145 ± 1 Ma) [73], Xiaohanshan monzogranite (144 ± 1 Ma) [79], Wulanchulute granite (142 ± 1 and 140 ± 1 Ma) [40], Wulandaba monzogranite (137 ± 1 Ma) [80], Haobugao mineralized granite (140 ± 1 Ma), post-mineralized granite (131 ± 1 Ma) [81], Huanggang granite porphyry (137 ± 1 Ma) [82] and Menghewula granite (134 ± 1 Ma) [73]. A large amount of evidence indicates that the most intense period of magmatic activity in this area occurred 145~125 million years ago ( Figure 10, Table S4). ...
... The elemental characteristics of granite porphyries B02 and B10 show high SiO2, K2O, Fe/(Fe + Mg), A/NK, K2O/Na2O and Ga/Al ratios and are Na-rich, Ca-poor, enriched in Rb, Th, U, Ta, Nd, Zr and Hf and depleted in Ba, Sr, P, Eu and Ti. These characteristics are similar in A-type granites [38,40,77]. Y and Nb are depleted compared to other A-granites because of the amphiboles and other minerals crystallized during the formation of the Haobugao granite porphyry [85]. ...
In the Huanggangliang–Ganzhuermiao metallogenic belt in the southern Great Xing’an Range, the Haobugao Pb‒Zn deposit is the most widespread skarn-type polymetallic deposit. The observed mineralization processes in this area are closely associated with both magmatic and tectonic activity. The zircon U‒Pb ages of two granitoid phases are 134.0 ± 0.6 Ma and 133.4 ± 0.9 Ma (Early Cretaceous). High SiO2 content (average mass fractions of 77.98 wt.% and 73.25 wt.%), high alkalinity (average mass fractions of 6.19 wt.% and 8.78 wt.%), and low CaO levels (average mass fractions of 0.16 wt.% and 0.12 wt.%) are characteristic of these rocks. They are also enriched in high-field-strength elements (HFSEs) (Th, U, Ta, Zr, Hf, etc.) and depleted in large ion lithophile elements (LILEs) (Ba, Sr, etc.). Furthermore, the Nb/Ta ratios (7.80~8.82, 10.00~10.83) point to a crustal origin of the magma. The zircon Hf isotopic compositions suggest that the melting of young crust derived from Meso-Neoproterozoic and Neoproterozoic depleted mantle gave rise to the magma in these granite porphyries. These rocks formed in an extensional environment driven by the subduction and retreat of the Paleo-Pacific plate during the Early Cretaceous.
... This calculation needs to remove the samples that do not meet the requirements, such as La > 1 × 10 −6 , Th/U < 0.1, and SiO 2 > 75% in the whole-rock chemistry [71,72]. We calculated the variation in crustal thickness from the Early Devonian to Early Cretaceous in the research area ( Figure 10) based on the data from this paper and other researchers (Table 4) [30,36,39,[73][74][75][76][77]. The crustal thickness in the Early Devonian is relatively thin (~28.52 km), but it increased to 43.13 km during the Middle Devonian. ...
... This calculation needs to remove the samples that do not meet the requirements, such as La > 1 × 10 −6 , Th/U < 0.1, and SiO2 > 75% in the whole-rock chemistry [71,72]. We calculated the variation in crustal thickness from the Early Devonian to Early Cretaceous in the research area ( Figure 10) based on the data from this paper and other researchers (Table 4) [30,36,39,[73][74][75][76][77]. The crustal thickness in the Early Devonian is relatively thin (~28.52 km), but it increased to 43.13 km during the Middle Devonian. ...
The Uhelchulu quartz diorite-granodiorite intrusions in Xiwuqi, Inner Mongolia, are exposed along the northwestern margin of the Xilinhot microcontinental block, located within the central and eastern parts of the southeastern Hegenshan suture zone. LA-ICP-MS zircon U-Pb dating yielded crystallization ages of (396 ± 8) Ma for the quartz diorite and (385 ± 5) Ma for the granodiorite, indicating an Early-Middle Devonian magmatic event. The quartz diorite exhibits I-type granite features, characterized by elevated Al2O3 (14.33–15.43 wt%), MgO (3.73–5.62 wt%), and Na (Na2O/K2O = 1.04–1.44), coupled with low P2O5 (0.15–0.20 wt%) and TiO2 (0.73–0.99 wt%). Trace element patterns show relative enrichments in Rb, Th, U, and Pb, while Nb, Ta, Sr and Ti are relatively depleted. Total REE contents are relatively low (123–178 ppm), with significant LREE enrichment (ΣLREE/ΣHREE = 4.75–5.20), and a non-obvious Eu anomaly (δEu = 0.75–0.84). In contrast, the granodiorite displays S-type granite characteristics, with high SiO2 (70.48–73.01 wt%), K (K2O/Na2O = 1.35–1.83), Al2O3 (A/CNK = 1.16–1.31), and a high differentiation index (DI = 76–82). Notably, MgO (1.44–2.24 wt%) contents are low, and significant depletions of Ba, Sr, Ti, and Eu are observed, while Rb, Pb, Th, U, Zr, and Hf are significantly enriched. Total REE contents are relatively low (178–314 ppm), exhibiting significant LREE enrichment (LREE/HREE = 6.17–8.36) and a pronounced negative Eu anomaly (δEu = 0.34–0.49). The overall characteristics point towards an active continental margin arc background for the Uhelchulu intrusions. Previous studies have suggested that the Hegenshan ocean continuously subducted northward from the Early Carboniferous to the Late Permian, but there is a lack of evidence for its geological evolution during the pre-Early Carboniferous. Therefore, this paper provides a certain basis for studying the geological evolution during the pre-Early Carboniferous in the Hegenshan ocean. We preliminarily believed that the Hegenshan ocean underwent a southward subduction towards the Xilinhot microcontinental block in the Xiwuqi area, at least from the Early Devonian to the Middle Devonian and the Hegenshan ocean may might have undergone a shift in subduction mechanism during the Late Devonian or Early Carboniferous.
The Haobugao Pb–Zn deposit located in the southern Great Xing’an Range (SGXR) is one of the most important deposits within the Huanggangliang–Ganzhuermiao polymetallic metallogenic belt. Xiaohanshan quartz monzonite porphyry and Wulandaba granodiorite are present in the ore area and are assumed to be closely related to the mineralization. In this study, a new isotopic dating technique, zircon U–Pb laser ablation inductively coupled plasma mass spectrometer analysis, was applied to the granites; the analyses indicate that the Xiaohanshan quartz monzonite porphyry and Wulandaba granodiorite were emplaced at 143.9 ± 1.1 Ma and 151.3 ± 1.4 Ma, respectively. Geochemically, these A-type granites are characterized by relatively high SiO2 and K2O contents, low Al2O3 content, and negative Eu anomalies. Additionally, both granites display strong Rb, Th, U, and Ce enrichment and Ba, K, Sr, and Ti depletion. Their relatively high εHf (t) values (with averages of 7.13 and 7.87, respectively) and young two-stage Nd and Hf model ages indicate that the two granites may have predominantly derived from the partial melting of a juvenile lower crust, followed by fractional crystallization during magma ascent. The geological, elemental, and isotopic evidence shows that the Xiaohanshan quartz monzonite porphyry and Wulandaba granodiorite formed due to the upwelling of mantle-derived alkaline magma and partial melting of the crust, with a certain degree of mixed dyeing, under a tectonic background of asthenosphere upwelling and lithosphere extension via the subduction of the ancient Pacific plate.
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