Article

Stratigraphical sequence of carboniferous marine volcanic-deposit rock and its geological age in Jueluotage area, eastern Tianshan

Authors:
  • Nanjing Institute of Geology and palaeontology, CAS
To read the full-text of this research, you can request a copy directly from the authors.

Abstract

By the study on the Carboniferous biostratigraphy and geological age in Lubaishan, Jiabaishan and Yamansu areas in Jueluotage, the Carboniferous sequence is revised, and the fusulinid zone, coral assemblages and brachiopod assemblages are divided. It is suggested that the geological age of Lower and Middle member of Yamansu Formation is Jiusian-Shangsian in the Early Carboniferous; while the Upper member is Dewuan, and the strata of volcanic deposit which is correlated with the marine volcanic type iron is Jiusian. What's more, these fossil assemblages indicate that the age of Dikanr Formation is Luosuan in the Late Carboniferous, and the age of Tugutu Bulak Formation is Huashibanian, volcanics horizon here was forming in Huashiba-nian. Besides, this paper suggests that the Xiaorequanzi Formation should be abandoned since this formation can belong to the Middle-Lower part of Yamansu Formation in this area. The geotectonic background of Carboniferous is also discussed in this paper.

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the authors.

... Numerous studies show that the TOB was generated by the subduction and closure of Paleo-Asian Ocean and abundant Phanerozoic magmatic rocks were exposed in this orogenic belt, especially the Late Carboniferous to Permian rocks (e.g. Shu et al. 2004;Wang et al. 2007Wang et al. , 2018Wu et al. 2006;Zhou et al. 2010;Zhang et al. 2012aZhang et al. , 2012bLei et al. 2013;Hou et al. 2014;Zheng 2015;Luo et al. 2012Luo et al. , 2016Zhang et al. 2016, Zhao et al., 2017Zhao et al. 2018b;Du et al. 2018aDu et al. , 2018bDu et al. , 2021Safonova et al. 2017;Long et al. 2020). Eastern Tianshan, as the eastern segment of the TOB, is mostly covered by the Gobi. ...
... The lithology of the YF can be divided into three members: (i) the bottom, mafic to intermediate-acid tuff, lava breccia and medium-to fine-grained sandstone with minor intercalation of bioclastic limestone; (ii) the middle, limestone (i.e. bioclastic and microcrystalline limestone) with some grey-green volcanic breccia, coarse-grained or coarse-grains-containing sandstone and tuffaceous sandstone (Zhang et al., 2012b); and (iii) the uppermost, limestone, tuff sandstone with minor tuff (Qin et al. 2002;Hou et al. 2014). The volcanic lavas of the TF are mainly distributed in the southern part of the Aqishan-Yamansu Belt and also can be divided into three sections, i.e. (i) the lower section of fuchsia andesite, rhyolite, crystalline tuff with minor fuchsia tuff and tuff sandstone; (ii) the middle section of sedimentary pyroclastic rocks with bioclastic or bioclastic limestone, volcanic breccia and tuffaceous Du et al. (2018a) and Zhao et al. (2018aZhao et al. ( , 2018b. ...
... Blue data are ages of intrusive rocks, pink data are ages of volcanic rocks. sandstone; and (iii) the uppermost section of purplishgray andesite and grey basalt, with minor interlayers of aubergine rhyolite and sandstone (Zhang et al., 2012b;Zhang et al. 2016). In addition, the Carboniferous (303- 307 Ma,[314][315][316][317][318] and Permian (243)(244)(245)(246)(247)(248)(249)(250)(251)(252) intrusions are widely developed in the Aqishan-Yamansu Belt (Figure 1(c); (Wu et al. 2006;Zhou et al. 2010;Lei et al. 2013;Zhang et al. 2013Zhang et al. , 2016Zheng 2015;Du et al. 2018a). ...
Article
New geochronological and geochemical data were presented for the Early Carboniferous basaltic to andesitic volcanic rocks and Late Carboniferous granitic intrusions in the Aqishan–Yamansu Belt of Eastern Tianshan, NW China. Zircon U–Pb dating indicates that the andesite and granite were emplaced at 330 Ma and 321 Ma, respectively. The andesitic rocks of the Yamansu Formation (FM) display subalkaline to calc-alkaline characteristics with moderate SiO2, relatively high Mg# values, and low Cr, Co and Ni, indicating an origin from mantle-derived melts. Their relatively low εNd(t) values (–0.02 ~ +0.61) and old TDM ages (TDM = 1.39–1.40 Ga) suggest a mantle source with addition of old crustal materials. Their high Rb/Y and Ba/La, low Nb/Y and Th/Yb ratios elucidate that the magma sources were probably metasomatized by slab-derived fluids. Besides, the high Th and low Ce/Th and Ba/Th ratios of the andesites suggest a contribution from subducted sediment–derived melts. Integrated with the depletion in high field strength elements and enrichment in light rare earth elements (LREEs), we suggest that the Yamansu andesites were formed by partial melting of relatively enriched mantle wedge metasomatized by both subducted sediment-derived melts and fluids. The basalts of the Tugutublak Formation (TF) have high MgO, Mg# (56–58) and εNd(t) (+5.9 ~ +6.3) values with enriched in LREEs and depleted in Nb–Ta–Ti anomalies, implying an arc setting. Their high Ba/Th, Ba/La and low Th/Ta, Th/Yb ratios suggest that the slab-derived fluids were involved. The basaltic andesites of the TF have higher SiO2, lower Mg# (48–50), Cr, Ni and εNd(t) (+1.21) values than the basalts of this formation, indicating that they were evolved from the basaltic magma. Therefore, the Carboniferous volcanic rocks in this study indicate that the Aqishan–Yamansu Belt was in a subduction background. The granites intruding into the TF show typical characteristics of I-type granite. Their highly positive εHf(t) values (+14 ~ +17) suggest a significant contribution from juvenile basaltic lower crust. Moreover, changes in the Dy/Yb and Ho/Yb ratios of Late Paleozoic felsic igneous rocks in the Aqishan–Yamansu Belt imply that the crust underwent four periods of thickening and thinning, which were likely triggered by the variation of subduction angles.
... The Aqishan-Yamansu belt in the Chinese Eastern Tianshan Orogen (Xinjiang, NW China) contains an important yet special Fe-(Cu) mineralization system, as represented by the Aqishan, Hongyuntan, Bailingshan, Duotoushan, Heijianshan and Shaquanzi deposits Zhang et al., 2012;Huang et al., 2013;Hou et al., 2014a,b). These deposits are commonly hosted in submarine volcanicsedimentary rocks and characterized by extensive skarn alteration, yet the alteration lacks unambiguous spatial links with intrusive rocks (Mao et al., 2005). ...
... 336 Ma; Luo et al., 2016), volcaniclastic and clastic rocks (Zhang, 2008). Recent stratigraphic and paleontologic studies suggested that the Tugutublak Formation contains submarine lava, tuff and sandstone, as well as terrigenous andesite, dacitic and crystal tuff (Zhang, 2008;Zhang et al., 2012;Fig. 2). ...
... Minor Triassic post-collisional granitoids were also documented, including the Tudun granite (246.2 ± 2.6 Ma; Zhou et al., 2010) and the Yamansubei granite (227.9 ± 0.47 Ma; Lei et al., 2013). Important highgrade Fe-(Cu) deposits in the region include Aqishan, Hongyuntan, Bailingshan, Duotoushan, Heijianshan, Yamansu and Shaquanzi Mao et al., 2005; Z.J. Zhang et al., 2012;Huang et al., 2013;Han et al., 2010;Hou et al., 2014a,b;Jiang et al., 2016;Zhao et al., 2017a,b). ...
Article
Tourmaline is an important B-bearing mineral in many types of hydrothermal deposits, and its chemical and boron isotopic signatures shed light on the nature and evolution of the metallogenic processes. Two generations of hydrothermal tourmaline in potassic-altered rocks (tourmaline I) and subsequent veinlets (tourmaline II) have been identified at the volcanic-hosted Bailingshan Fe deposit in the Chinese Eastern Tianshan, NW China. Both tourmaline I and II have low Ca contents and X-site occupancy, and belong to the alkali group. Tourmaline I grains plot in the schorl field or between the dravite and schorl fields, whereas tourmaline II grains are largely Mg-rich dravitic. Mineral textural and geochemical features suggest that the compositions of tourmaline I and II were mainly controlled by the host rock and hydrothermal fluid compositions, respectively. In-situ B-isotope analyses of tourmaline I yielded δ¹¹B values of +1.7‰ to +4.1‰, whereas tourmaline II yielded slightly higher values of +3.5‰ to +6.6‰. Calculated B-isotope compositions (δ¹¹BH2O) of the hydrothermal fluids in equilibrium with tourmaline I are +3.3‰ to +5.7‰ (at 550 °C), suggesting a mixed magmatic fluid (major) and basinal brine (minor) origin. Meanwhile, tourmaline II-forming fluids yielded δ¹¹BH2O values of +6.2‰ to +9.3‰ (at 400 °C). Based on geological constraints and modal calculations, we suggest that the observed B-isotope variations from tourmaline I to II are mainly controlled by Rayleigh fractionation process, and indicate that they may have crystallized from similar fluids. The presence of basinal brine incursion into the K-rich hydrothermal fluids and geological constraints lead us to suggest that the Bailingshan deposit was likely formed in a Paleozoic Aqishan-Yamansu arc-related basin in the Eastern Tianshan.
... Abundant fossils occur in the Lubaishan and Jiabaishan areas, including corals Heterophyllia and Zaphrentites which has been grouped into the Meniscophyllum xinjiangense Assemblage (Cai, 1988), brachiopods Eochoristites, Antiquatonia inflata, and Marginifera cf. timanica, and echinoderms Ellipsoellipticus and Cyclocyclicus, all of which indicates late Tournaisian-early Visean in age (Zhang et al., 2012). ...
... The lower member of the Formation yields corals Hunanoclisia, Dibunophyllum cf. bipartitum, Arachnolasma, and Auloclisia, indicating Visean in age (Zhang et al., 2012). In the middle member of the formation, the corals Gangamophyllum-Palaeosmilia-Kueichouphyllum Assemblage and conodont Gnathodus bilineatus romulus were discovered by Huang et al. (2021a), which indicate late Visean to early Serpukhovian in age (Qi et al., 2014). ...
Article
The Carboniferous is the most widely distributed system in the pre-Mesozoic strata of Xinjiang, Northwest China, and they are exposed in structurally independent units within various tectonic settings across the southwest Central Asian Orogenic Belt and Tarim Craton in Northwest China. According to the lithofacies associations and biotic assemblages, the Carboniferous successions of Xinjiang can be divided into 18 stratal regions, and each of these stratal regions may be further separated into several subregions in terms of lithology, biota, and geochronologic data. The depositional succession of each region is described on the basis of the key section. The marine fossils such as foraminifers (fusulinids), brachiopods, corals, and conodonts, as well as nonmarine fossils such as plants and pollens are reviewed in this study. Combined with the geochronologic data from the volcanic rocks and ash layers, a refined scheme of the Carboniferous successions in different regions across Xinjiang, Northwest China is obtained. The detailed and newly established stratigraphic framework of the Carboniferous strata could be very helpful for the regional and global stratigraphic correlations. It can also offer a new and reliable chronostratigraphic foundation for the comprehensive understanding of the tectonic evolution and petroleum exploration in Central Asia.
... The Aqishan-Yamansu belt is bounded by the Yamansu Fault in the north and by the Aqikekuduke Fault in the south (Figure 1). Strata exposed in this belt comprise mainly Carboniferous volcanicvolcaniclastic rocks with intercalated sedimentary rocks (Zhang, Huang, et al., 2012;Zhang, Sun et al., 2012;Zhang, Chen, et al., 2021;Zhang, Deng, Tu, Peng, & Jin, 2021). The voluminous volcanism has been further divided into two stratigraphic members, that is, the Yamansu and Tugutublak formations. ...
... The voluminous volcanism has been further divided into two stratigraphic members, that is, the Yamansu and Tugutublak formations. Stratigraphic and palaeontologic studies suggested that the Yamansu Formation was dominated by submarine mafic to felsic volcanic and volcaniclastic rocks, whereas the Tugutublak Formation contains submarine as well as terrigenous andesitic-dacitic lava and volcaniclastic rocks (Zhang, Huang, et al., 2012;Zhang, Sun et al., 2012). Zircon U-Pb dating yielded ages of 336 ± 2 Ma (Luo et al., 2016) and 324.1 ± 2.1 Ma for the Yamansu and Tugutublak formations, respectively. ...
Article
As a common Ca‐ and Ti‐ bearing silicate mineral in many types of hydrothermal deposits, titanite usually contains high concentrations of trace elements. Its mineral chemistry and U–Pb isotope can reveal the physicochemical conditions and geochronology of the ore‐forming systems. In this contribution, we present a detailed study on titanite which precipitated during the Fe mineralization in the Duotoushan deposit. Due to coexistence with hydrothermal minerals, low Th/U ratios (0.02–0.3), and depletion in rare earth elements (REE), all the studied titanites are classified into a hydrothermal group. The negative correlation between [REE3+ + (Al, Fe)3+] and [Ca2+ + Ti4+] indicates that REE mainly entered the lattice of titanite via the mechanism of substitution. In addition, titanite grains are characterized by HREE, Zr, and Nb enrichments with LREE depletion, suggesting that the complexation of F− at neutral to alkaline pH conditions may have caused the fractionation of REE. At Duotoushan, the titanite grains coexist with quartz, epidote, amphibole, and magnetite, and exhibit positive Eu anomalies (δEu = 1.04–1.31) but lack Ce anomalies, indicating that ore‐forming fluids may have been derived from a relatively low oxygen fugacity and high fH2O environment. Titanite yielded an in‐situ U–Pb lower‐intercept age of 307.2 ± 4.8 Ma (MSWD = 0.97), consistent with the syn‐ore amphibole 40Ar‐39Ar plateau age (305 ± 6 Ma). Since the mineralization ages are obviously younger than country rocks, the previous syn‐sedimentary ore‐forming model for Duotoushan Fe–Cu mineralization can be excluded. Integrating the characteristics from ore deposit geology, periods of mineralization events, and spatial–temporal distribution of magmatism, we proposed that the Duotoushan Fe–Cu mineralization event may be linked with a hidden granite in its orefield. Hydrothermal titanite U–Pb and amphibole 40Ar‐39Ar dating on the Duotoushan mineralization yielded a Late Carboniferous age. The Duotoushan magnetite precipitated under relatively reduced, neutral to alkaline pH and H2O‐rich conditions.
... The Kanggur shear zone (about 400 km long and 20 km wide) contains dominantly Carboniferous volcaniclastic rocks, clastic rocks and ophiolite fragments, most of which are ductile deformed (Mao et al., 2005;Li et al., 2006). Abundant Permian mafic-ultramafic intrusions and important Cu-Ni sulfide deposits were formed in the eastern Kanggur shear zone (Han et al., 2010;Zhang et al., 2012;Deng et al., 2015). Besides, some syn-or post-collisional-related orogenic Au and porphyry Mo deposits were formed at ca. 280 -230 Ma (Zhang et al., 2015;Wang and Zhang, 2016;Wu et al., 2017). ...
... The Aqishan-Yamansu belt comprises mainly Carboniferous intermediate-felsic volcanic-volcaniclastic rocks with minor marine sediment interbeds (Zhang et al., 2012;Han et al., 2019). These sequences are widely intruded by Carboniferous-Permian granitoids, which include the Bailingshan intrusive complex, Hongyuntan granodiorite and Xifengshan granite (Zhou et al., 2010;Zhang et al., 2016). ...
Article
Full-text available
In this study, we conducted zircon U-Pb dating, and whole-rock geochemical and Sr-Nd isotope analyses on the Late Mesozoic dolerite dykes in the Bailingshan Fe deposit (Eastern Tianshan Orogen, NW China) to unravel their petrogenesis and regional tectonic significance. Zircon U-Pb dating on the dolerite yielded an Early Cretaceous age of 129.7 ± 1.4 Ma. The dolerite is calc-alkaline sodic (Na2O/K2O = 4.71 to 6.80), and enriched in LILEs (Rb, K, Sr, and Pb) but depleted in HFSEs (Nb, Ta, and Ti). The intermediate Nb/U (16.7 to 18.5) and Ce/Pb (6.33 to 6.90) values, and the presence of xenocrystic zircons in these dolerite dykes suggest crustal assimilation during the magma evolution. Petrological modeling suggests fractionation of olivine, pyroxene, garnet, and spinel. All the dolerite samples have low initial 87Sr/86Sr (0.7041 to 0.7043) and positive εNd(t) (+ 4.6 to + 5.1) values, indicative of a depleted asthenospheric mantle source. Partial melting modeling suggests that the melting has occurred in the spinel-garnet stability field. Integrating the data from ore deposit geology, geochronology, geochemistry and Sr-Nd isotopes, we proposed that the Late Cretaceous Eastern Tianshan mafic magmatism was developed in an intraplate extension setting.
... F I G U R E 1 (a) Simplified tectonic map of the Central Asian Orogenic Belt (modified after Jahn, Wu, and Chen (2000)); (b) Sketch map of Xinjiang Uygur Autonomous Region, NW China (modified after Liu, Xu, and He (2013) (BGMRXUAR, 1999;Wang, 1988;Wu & Wang, 1983;X. H. Zhang et al., 2012). Most of these species have a wide geographic distribution in the Palaeotethys during the Moscovian Age (L. X. Zhang et al., 2010). However, there is little documentation of younger fusulinids or other faunas in the region, which prevents us from understanding the palaeobiogeography of the North Tianshan belt. ...
Article
A noteworthy late Pennsylvanian fusulinid fauna is for the first time reported from the Qi'eshan Formation in the Eastern Tianshan, NW China. From three main outcrop sections, 19 species of six genera are identified and illustrated, among which several index taxa are described in detail. The present fusulinids are assigned to the middle Kasimovian to early Gzhelian in age, representing the youngest fusulinid fauna in northern Xinjiang up to now, which constrains the age of the Qi'eshan Formation up to the early Gzhelian. Palaeobiogeographically, the fusulinid fauna in the Eastern Tianshan was closely related to the populations from Central Asia (e.g., southern Fergana, the Alay Mountains and Darvaz) of the western Palaeotethyan Subprovince, and kept exchanging with those from the Eastern European Platform of Ural Province, given the common, particularly endemic species. The characteristic species include Montiparus ex gr. sinuosus alaicus, Rauserites rossicus, Schwageriniformis fusiformis, Triticites acutus, Triticites arcticus, and Triticites arcticus cybaeus. This palaeobiogeographic affinity suggests that the close of timing of the North Tianshan Ocean was later than the Early Gzhelian, and that the southern Urals and western Palaeotethys shared a common fusulinid fauna during this period. For the first time, a Middle Kasimovian to Early Gzhelian fusulinid fauna is reported in the North Tianshan Belt, NW China. Several typical species are shared in the Ural Province, the western Palaeotethyan Subprovince, and study area, suggesting the final closure time of the North Tianshan Ocean was posterior to the early Gzhelian.
... Similar tectonic setting and associated HMAs have been proposed in the Shiquanhe arc-related basin (e.g., back-arc basin) in the western Bangong suture, Tibet (Liu et al., 2018). Furthermore, the Aqishan-Yamansu belt is mainly composed of the Early Carboniferous Yamansu and Late Carboniferous Matoutan formations that consist of submarine to subterrestrial volcanic, volcaniclastic, and minor sedimentary rocks, with Carboniferous marine fossils (e.g., Yuanophyllum sp.; Zhang et al., 2012b), indicating the Aqishan-Yamansu belt was a Carboniferous basin. The Early Carboniferous rhyolite and granite porphyries from the Hongshanliang copper deposit district have similar ε Nd (t) values to the Precambrian basement rocks of Yili-Central Tianshan block (Zhao et al., 2019b), and Luo et al. (2012) reported that inherited zircons from the felsic volcanic rocks in the Yamansu Formation had similar age peaks (ca. ...
Article
The Aqishan-Yamansu belt, Eastern Tianshan is characterized by voluminous Late Paleozoic intermediate–felsic igneous rocks and magmatic–hydrothermal Fe (–Cu) deposits. This study presents zircon U–Pb ages and whole-rock geochemistry of newly identified high-Mg andesitic and dioritic rocks (HMAs and HMDs) within the Hongshanliang copper district in the Aqishan-Yamansu belt, Eastern Tianshan to investigate their petrogenesis and constrain the Carboniferous tectonic setting of the Eastern Tianshan. Zircon U–Pb dating of the HMAs and HMDs yielded ages between 336.9 ± 1.9 Ma and 329.0 ± 4.2 Ma. The HMAs and HMDs show calc-alkaline affinities, and exhibit weak Rb, Ba, U, and Pb enrichment and Nb and Ta depletion, with minor negative Eu anomalies. Moreover, the positive εNd(t) values (+6.4 to +6.6), low Th and (La/Sm)N contents/ratios, as well as relatively low and variable εHf(t) values (−3.71 to +1.55) indicate that they were probably sourced from a depleted mantle wedge with negligible to minor crustal contamination. They have low Ba/Th ratios (10.8–93.3), minor negative Eu anomalies, high and variable (La/Sm)N and Th/Yb ratios, which are comparable to the well-known sanukites of the Setouchi volcanic belt, suggesting involvement of sediment-derived magmas during their formation. Integrating published regional mafic–intermediate rocks from the Aqishan-Yamansu belt and this study, we propose that the Hongshanliang high-Mg rocks formed in a continental arc-related setting in the Carboniferous and the belt underwent a sharp tectonic transition event (ca. 330–322 Ma) from the Kangguer oceanic slab steepening to breakoff, corresponding to the Late Carboniferous basin inversion.
... Evidence of Carboniferous sedimentation in an island arc environment (Zhou et al. 2001;Zhang et al. 2012), the presence of ophiolite mélange (Li et al. 2000) and relict oceanic crust (He et al. 2005) near the Kuguertage faults, and the emplacement of adakitic porphyry Cu deposits derived from the partial melting of subducted oceanic crust (Han et al. 2006;Zhang et al. 2006;Wang et al. 2015) suggest that the area between the Kuguertage and Aqikuduke faults represents the suture zone (K-A Suture Zone, Figure 11) of the JOB (Muhetaer et al. 2009;Cao et al. 2016). Furthermore, we conclude that the Carboniferous volcanics in the JOB formed in a complex trench-arc-basin system. ...
Article
Full-text available
The major and trace element, and Sr–Nd isotopic compositions of the Carboniferous Qi’eshan, Wutongwozi, and Yamansu volcanic rocks from the northern and southern parts of the Jueluotage Orogenic Belt in East Tianshan, China, were analysed to understand their genesis and geodynamic implications. The early Carboniferous Qi’eshan basalts are characterized by high Al2O3, with La/Sm (1.38–1.79) and Ba/La (27.06–58.76) values higher than those of typical normal mid-ocean ridge basalt. They are relatively enriched in large ion lithophile elements (LILE) and light rare earth elements (LREE), and depleted in high field strength elements. Overall, their initial Nd–Sr isotopic compositions are εNd(t) = (5.6–7.0) and Isr = 0.70397–0.70429, implying the magma originated from a mantle wedge source that was metasomatized by subduction-related fluids. In contrast, the late Carboniferous Wutongwozi basalts have lower Ba/La (4.86–12.82), La/Nb (0.87–2.45), and LILE concentrations. They have the isotopic characteristics of depleted asthenosphere, relatively high and heterogeneous εNd(t) (9.3–9.4), and high Isr (0.70471–0.70533). Thus, the late Carboniferous Wutongwozi basalts may have been derived from the partial melting of mantle sources during asthenospheric upwelling. The early Carboniferous Yamansu acid volcanic rocks are characterized by high Mg# (46–48) and Lu/Y (~0.15), and low K2O/Na2O (0.01–0.20), similar to M-type granites. However, their εNd(t) (5.0–5.5) and Isr (0.70642–0.70768) values are lower than those of depleted mantle, indicating they were contaminated by lower crustal material. The magma source originated from a mantle-derived magma that was contaminated by middle Tianshan massif in a continental margin arc setting. Based on the results and previous field-based studies, we conclude that the Carboniferous volcanics in the Jueluotage Orogenic Belt formed in a complex trench–arc–basin setting in the Kuguertage–Aqikuduke Suture Zone.
... Lower Permian volcanic rocks recognized locally in the Kangguertag area unconformably overlie the Carboniferous se- quence and are in turn overlain by middle and upper Permian arkose, which is interlayered with conglomerate (BGMRXUAR, 1993 . Rocks of the Yamansu Formation are mainly exposed in the northern part of the Aqishan-Yamansu belt and have some index fossils, such as Arachnolasma, Gigantoprductus and Yuanophyllum (Zhang et al., 2012; W.F. , whereas rocks of the Tugutublak Formation are distributed in the southern part and have corals and fusulinids within the intercalated limestone ( Zhang et al., 2012;W.F. Zhang et al., 2016). ...
Article
Late Paleozoic is a key period for the accretion and collision of the southern Central Asian Orogenic Belt (CAOB). Here, we present new zircon U–Pb ages, whole-rock geochemistry and Sr–Nd isotopic compositions for four Late Paleozoic felsic plutons in Eastern Tianshan (or Tienshan in some literatures) in order to constrain the tectonic evolution of the southern CAOB. The granodioritic pluton and its dioritic enclaves were synchronously formed in the Early Carboniferous (336 ± 3 Ma and 335 ± 2 Ma, respectively). These rocks are depleted in Nb, Ta and Ti, and enriched in Rb, Ba, Th and U related to the primitive mantle, which show typical features of arc rocks. They both have similar Sr–Nd isotopic ratios to those granitic rocks from the eastern Central Tianshan Block and have the latest Mesoproterozoic two stage Nd model ages (TDM²) (1111–1195 Ma for the granodioritic pluton and 1104–1108 Ma for the enclaves, respectively), indicating that their source magmas may have been derived from the Mesoproterozoic crust. The albitophyric pluton was also emplaced in the Early Carboniferous (333 ± 3 Ma). Rocks of this pluton have similar εNd(t) values (−0.69 to −0.37) and TDM² ages (1135–1161 Ma) to those of the granodioritic rocks, suggest similar crustal source for both types of rocks. In contrast, the K-feldspar granitic and monzonitic plutons were emplaced in the Early Permian (292 ± 3 Ma and 281 ± 2 Ma, respectively). Samples of the K-feldspar granitic pluton have high K2O + Na2O, FeO/MgO, Ga/Al, HFSE (e.g., Zr and Hf) and low CaO, Sr and Ba, exhibiting characteristics of A2-type granites, which probably emplaced in a post-collisional extension environment. They have higher εNd(t) values (+2.77 to +3.27) and more juvenile TDM² ages (799–841 Ma) than the Early Carboniferous plutons, suggesting that they were derived from relatively younger crustal sources. The monzonitic granites are metaluminous to weakly peraluminous with A/CNK ranging from 0.93 to 1.05, and have very low P2O5, indicating characteristics of I-type granites. They also have positive εNd(t) values (+2.22 to +2.34) and juvenile TDM² ages (868–878 Ma), suggesting this pluton was also produced by partial melting of relatively young crustal source. Based on an isotopic mixing simulation, significant mantle contributions were added to the magma source of both the Early Carboniferous and the Early Permian felsic rocks. The mantle contribution changes from ~60% in the Early Carboniferous to ~75% in the Early Permian. The remarkably increasing of mantle materials in the magma source of the felsic rocks in the Aqishan-Yamansu belt was most likely induced by the tectonic transition from an Early Carboniferous continental arc to an Early Permian post-collisional extension environment.
... Previous studies suggest an arcbackarc basin system for the Carboniferous Yamansu belt (Chen et al., 2003;Huang et al., 2014a;Hou et al., 2014b;Jiang et al., submitted): During the Carboniferous, the south-dipping Kangguer Ocean subduction may have occurred beneath the Central Tianshan massif, generating the continental arc-related Yamansu Formation calc-alkaline volcanic rocks (ca. 348-334 Ma) (Hou et al., 2006;Luo et al., 2012;Zhang et al., 2012). Subsequently, arc rifting may have occurred and formed the upper Yamansu Formation bimodal volcanic rocks and some granites (Chen et al., 2003;Hou et al., 2014b;Zhou et al., 2010). ...
Article
The Shaquanzi Fe–Cu deposit is an important Fe (–Cu) deposit in the Yamansu Fe mineralization belt, Eastern Tianshan. Five-stage (Stage I to V) hydrothermal alteration/mineralization have been recognized: The early skarn (Stage I) and late skarn (Stage II) stages are featured by extensive garnet and amphibole alteration, respectively. Magnetite mineralization stage (Stage III) is associated with pervasive K + Fe ± Ca alteration, forming magnetite, mushketovite, K-feldspar, epidote, magnetite, pyrite and quartz. Chalcopyrite mineralization stage (Stage IV) has an ore mineral assemblage of chalcopyrite, bornite, acicular hematite and sphalerite, accompanied with broad epidote + chlorite + calcite alteration. The late veins stage (Stage V) occurs mainly as epidote + calcite veins crosscutting the host rocks and earlier-stage minerals. Stage I hydrothermal fluids have high temperatures (> 600 °C), medium-high salinities, with magmatic δ¹⁸Ofluid = + 6‰ to + 11.7‰. Stage III ore-forming fluids are medium-high-temperature (ca. 470–570 °C) with medium salinity. Stage III minerals were formed under δDfluid = − 45.7‰ to − 24.3‰, δ¹⁸Ofluid = + 5.8‰ to + 9.1‰ and δ³⁴Sfluid = − 1.7‰ to + 4.7‰, indicative of magmatic fluids mixed with minor seawater. In contrast, Stage IV fluids have low temperatures (ca. 160 °C), medium-low salinities and are Ca-rich, with isotopic compositions reflecting basinal brine mixed with meteoric water (δ¹³Cfluid = − 6.6‰ to − 2.3‰; δ¹⁸Ofluid = − 3.3‰ to + 2.8‰ and δ³⁴Sfluid ≥ + 24.8‰). The Shaquanzi diorite (zircon U–Pb age: 298 ± 5 Ma) is broadly coeval with previous Re–Os ages of the Shaquanzi magnetite and pyrite (303 ± 12 Ma and 295 ± 7 Ma, respectively), indicating that the Shaquanzi Fe–Cu metallogeny may have been genetically linked to the regional magmatic–hydrothermal activities led by the Yamansu arc-backarc basin inversion. Features of hydrothermal alterations, mineral assemblages, ore-forming fluids and tectonic setting all suggest that the Shaquanzi Fe–Cu deposit is an IOCG-like deposit, similar to those in the Cenozoic Central Andes.
Article
Full-text available
The Xiaobaishitou gabbro–diorite pluton comprises a medium‐grained gabbro–diorite suite and a fine‐grained diorite suite, which intrude the Kawabulag Group in the East Tianshan Orogen of the Central Asian Orogenic Belt (CAOB). A combination of mineral chemistry, zircon U–Pb age, whole‐rock geochemistry, Sr‐Nd isotopes, and in situ zircon Hf isotopes for newly found gabbro‐diorite from the Xiaobaishitou district in the Central Tianshan Terrane (CTT) is presented to investigate the petrogenesis and tectonic or even crustal evolution of the East Tianshan Orogen. Laser ablation inductively coupled plasma mass spectrometry (LA–ICP–MS) zircon U–Pb analyses indicate that the gabbro‐diorite was formed at 324.7 ± 2.4 Ma. The isolated clinopyroxene formed under higher P–T–H2O melt conditions (10.7–14.6 kbar; 1199–1269 °C; high fO2) than those for the hornblende, plagioclase, and zircon (557–687 °C; moderate fO2) in the gabbro‐diorite, which reveals a multilevel, magmatic storage system. The gabbro‐diorite is characterized by fractioned REE patterns, enriched LILEs (e.g., Ba and Pb), negative anomalies of HFSEs (e.g., Nb and Ta), and low La/Yb and Sr/Y ratios, which are typically indicative of crustal contamination and accounted for by subduction‐related fluids. The rock also characterized by typical features of high compatible elements (MgO = 3.14 to 11.65 wt.%, Cr = 1 to 157 ppm, Ni = 6 to 830 ppm), high Mg# (47–74), positive εHf(t) values (+5.1 to +10.3; XBST17‐95) and εNd(t) values (+2.3 to +4.4; XBST17‐98, 99, 100, 102, 104, 105). These features suggest that the Xiaobaishitou gabbro‐diorite was most likely derived from metasomatic mantle and contaminated minor crustal components. Taking into account the spatial and temporal distribution of the Carboniferous magmatic rocks in the CTT, we suggest the formation of the Xiaobaishitou gabbro‐diorite was attributed to southward subduction of the Kangguer Ocean.
Article
The North Tianshan Ocean (NTO) was one of the youngest oceanic basins at the southwestern margin of the Central Asian Orogenic Belt. When, where and how the NTO was finally consumed and closed have not been well addressed. To better understand the tectonic evolution of the NTO, particularly before its closure, an integrated study of volcanic rocks in the Yamansu volcanic arc has been carried out. Two SHRIMP zircon U–Pb ages (317.6±3.1 Ma and 310.7±2.4 Ma) indicate that the previously identified Permian volcanic rocks erupted during the late Carboniferous instead. The late Carboniferous volcanics in the region are composed of bimodal suites with a SiO2 compositional gap between 60–70%. The mafic volcanics could be further divided into LREE-poor basalts and LREE-rich basalt-andesites. The LREE-poor variety displays tholeiite and forearc-like characteristics with flat to depleted LREE patterns with (La/Yb)N < 1.5, which were likely derived from a moderately depleted mantle wedge metasomatized by a subducted fluid-like component. The LREE-rich suite is calc-alkaline and has enriched LREE patterns with high (La/Yb)N > 2. They were from a depleted mantle wedge metasomatized by subducted sediment-derived melts, although more or less suffered crustal contamination. The felsic volcanics are I-type rhyolites, derived from anatexis of Cambrian to Mesoproterozoic arc crustal rocks. Here, we suggest that the Kanggur Fault presumably represented the southernmost suture of NTO. The Yamansu volcanic arc was a forearc system of the Central Tianshan continental arc related to southward subduction of the NTO.
Article
The Aqishan-Yamansu belt in the Chinese Eastern Tianshan represents a Paleozoic arc-related basin generally accompanied by accretionary magmatism and Fe-Cu mineralization. To characterize the tectonic evolution of such an arc-related basin and related magmatism and metallogenesis, we present a systematic study of the geochronology, whole-rock geochemistry, and Sr-Nd isotopes of igneous rocks from the belt. New zircon U-Pb ages, in combination with published data, reveal three phases of igneous activity in the Aqishan-Yamansu belt: early Carboniferous felsic igneous rocks (ca. 350−330 Ma), late Carboniferous intermediate to felsic igneous rocks (ca. 320−305 Ma), and Permian quartz diorite and diorite porphyry dikes (ca. 280−265 Ma). The early Carboniferous felsic rocks are enriched in large ion lithophile elements (LILEs) and depleted in Nb, Ta, and Ti, showing arc-related magma affinities. Their positive εNd(t) values (3.3−5.9) and corresponding depleted mantle model ages (TDM) of 0.83−0.61 Ga, as well as high MgO contents, Mg# values, and Nb/Ta ratios, suggest that they were derived from lower crust with involvement of mantle-derived magmas. The late Carboniferous intermediate igneous rocks show calc-alkaline affinities, exhibiting LILE enrichment and high field strength element (HFSE) depletion, with negative Nb and Ta anomalies. They have high MgO contents and Mg# values with positive εNd(t) values (3.9−7.9), and high Ba/La and Th/Yb ratios, implying a depleted mantle source metasomatized by slab-derived fluids and sediment or sediment-derived melts. The late Carboniferous felsic igneous rocks are metaluminous to peraluminous with characteristics of medium-K calc-alkaline I-type granites. Given the positive εNd(t) values (6.3−6.6) and TDM ages (0.56−0.53 Ga), we suggest the late Carboniferous felsic igneous rocks were produced by partial melting of a juvenile lower crust. The Permian dikes show characteristics of adakite rocks. They have relatively high MgO contents and Mg# values, and positive εNd(t) values (7.2−8.5), which suggest an origin from partial melting of a residual basaltic oceanic crust. We propose that the Aqishan-Yamansu belt was an extensional arc−related basin from ca. 350 to 330 Ma; this was followed by a relatively stable carbonate formation stage at ca. 330−320 Ma, when the Kangguer oceanic slab subducted beneath the Central Tianshan block. As the subduction continued, the Aqishan-Yamansu basin closed due to slab breakoff and rebound during ca. 320−305 Ma, which resulted in basin inversion and the emplacement of granitoids with contemporary Fe-Cu mineralization. During the Permian, the Aqishan-Yamansu belt was in postcollision extension stage, with Permian adakitic dikes formed by partial melting of a residual oceanic crust.
Article
The Aqishan-Yamansu belt in the Eastern Tianshan (NW China) contains many intermediate to felsic intrusive rocks and spatially and temporally associated Fe (-Cu) deposits. Zircon U-Pb dating of the Bailingshan granitoids, including diorite enclaves (in granodiorite), diorite, monzogranite and granodiorite, and andesitic tuff from the Shuanglong Fe-Cu deposit area yielded ages of 329.3 ± 2.1 Ma, 323.4 ± 2.6 Ma, 313.0 ± 2.0 Ma, 307.5 ± 1.7 Ma and 318.0 ± 2.0 Ma, respectively. These new ages, in combination with published data can be used to subdivide magmatism of the Bailingshan intrusive complex into three phases at ca. 329–323 Ma, ca. 318–313 Ma and ca. 308–297 Ma. Of the analyzed rocks of this study, the Shuanglong diorite enclave, diorite and andesitic tuff show calc-alkaline affinities, exhibiting LILE enrichment and HFSE depletion, with negative Nb and Ta anomalies. They have high MgO contents and Mg# values, with depleted εHf(t) and positive εNd(t) values, similar crustal-derived Nb/Ta and Y/Nb ratios, low Th/Yb and Th/Nb, and high Ba/La ratios, which are consistent with them being sourced from a depleted mantle wedge metasomatized by slab-derived fluids and crustal contamination. However, the monzogranite and granodiorite are metaluminous with characteristics of low- to high-K calc-alkaline I-type granites. The granitic rocks are enriched in LILE, depleted in HFSE and have significant Eu anomalies, with high Y contents and low Sr/Y ratios, resembling typical of normal arc magmas. Depleted εHf(t) and positive εNd(t) values with corresponding young TDMC ages of zircons, as well as Nb/Ta, Y/Nb, Th/U and La/Yb ratios suggest that the granitic rocks were probably formed by re-melting of juvenile lower crust or pre-existing mantle-derived mafic–intermediate igneous rocks. Integrating published data, we conclude that the Bailingshan granitoids (excluding the Shuanglong diorite and diorite enclave) were derived from re-melting of juvenile lower crust and mantle-derived mafic–intermediate igneous rocks, with mantle components playing a more prominent role in the formation of the younger and more felsic rocks. A comprehensive review, including our new data, suggests that the Aqishan-Yamansu belt formed as a fore-arc basin during the Carboniferous (ca. 350–300 Ma) when the Kangguer oceanic slab subducted beneath the Yili-Central Tianshan block. The ongoing southward subduction of the slab resulted in the closure of the Aqishan-Yamansu fore-arc basin (ca. 320–300 Ma), due to slab steepening and rollback followed by slab breakoff and rebound. During the Aqishan-Yamansu fore-arc basin inversion, the main phase of the Bailingshan granitoids emplaced in the Aqishan-Yamansu belt, accompanied by contemporary Fe and Fe-Cu mineralization.
Article
The Duotoushan Fe-Cu deposit is located in the western segment of the Aqishan-Yamansu metallogenic belt in Eastern Tianshan, Xinjiang (China). Magnetite orebodies are mainly developed in the Upper Carboniferous volcano-sedimentary rocks and are mostly stratabound. Pyrite Re-Os dating has yielded an isochron age of 312 ± 24 Ma (MSWD = 1.5). Five hydrothermal and one supergene alteration/mineralization stages have been recognized from the spatial distribution of alteration zoning, mineral assemblages and textural relationships. The earliest alteration of albite (Ab84-98Or2-16) ± amphibole was related to the nearby albitization granite porphyry. Prograde alteration was developed on the footwall of the intermediate-mafic volcanic rocks, and formed a garnet (Ad60-95Gr5-40)-clinopyroxene (Hd0Di93Jo7 to Hd10Di83Jo7) assemblage. Alteration associated with magnetite can be further divided into three sub-stages, consisting of magnetite-amphibole ± titanite (stage III-A), magnetite-amphibole-epidote (stage III-B) and epidote-magnetite-quartz ± amphibole ± titanite ± pyrite (stage III-C) mineral assemblages. The secondary amphibole is dominantly actinolite. Pyrite, with minor chlorite-chalcopyrite veins, cut the magnetite ore, followed by later quartz/calcite/hematite veinlets. Based on fluid inclusions (FIs) and stable isotopes studies, the pre-ore stage (stage II) was formed at high temperature (>500 °C) and originated from magmatic-hydrothermal fluids (δ18OH2O = +7.1‰, δDH2O = −85‰). Two garnet samples have similar δ18OH2O values (+5.6‰ and +6.4‰) but considerably lower δDH2O values (−134‰ and −139‰), indicating the overprinting by late meteoric water. Iron ore and hydrous minerals assemblages and the associated fluids had overprinted the early anhydrous minerals. Early magnetite mineralization stage (stage III-A) shows clear magmatic water input, as constrained from the δ18OH2O (+6.9‰ to +7.8‰) and δDH2O (−85‰ to −72‰) values. Later magnetite stage was magmatic-hydrothermal fluid-dominated, but with mixing of heavy δDH2O, as indicated by stable isotope compositions (δ18OH2O = +6.1‰ to +7.8‰, δDH2O = −47‰ to −32‰). Sulfur isotope values of the stage IV pyrite give a δ³⁴S interval of +8.8‰ to +12.1‰, suggesting significant addition of external basin fluid/seawater or evaporite sulfur source to magmatic fluid. The low temperatures (83‒213 °C, average = 135 °C), generally medium-high but variable salinities (9.9‒27.2 wt.% NaCl equiv., average = 21.3 wt.%) and Ca-Mg-rich components of stage V fluids show clear features of involvement of basinal brines/seawater and minor meteoric water in the late hydrothermal stages. We infer that the temperature drop of the hydrothermal fluids may have been the main cause of massive magnetite precipitation at the Duotoushan deposit, whereas increasing pH values, decreasing temperature and fluid mixing maybe responsible for Cu precipitation. Ore deposit geology, mineral geochemistry and fluid evolution confirm that the Duotoushan Fe-Cu deposit is different from typical skarns and may represent a distinct group of Fe (-Cu) deposits formed during the Aqishan-Yamansu back (intra-) arc basin inversion, which show many similarities with the Central Andean IOCG deposits.
Article
Carboniferous volcanic rocks are widely distributed in northern Alashan League and its neighboring areas, and their genesis and tectonic setting have always been an issue of controversy. Based on analysis of petrology and petrogeochemistry characteristics of Carboniferous volcanic rocks in the study area, this paper attempts to clarify the palaeo-tectonic setting and provides independent evidence for understanding the properties of Carboniferous basin. The volcanic rocks are dominated by intermediate-acidic volcanic rock. The majority of basalts, basaltic-andesite and andesite fall into sub-alkaline series. Mg# number of this suit ranges from 0.29 to 0.69. These volcanic rocks samples exhibit strong depletion in the high field strength elements Nb, Ta and Ti, and minor enrichment in the LREE. In terms of REE, (La/Yb)N number ranges from 2.19 to 10.10, showing less obvious Eu depletion (δEu=0.81 to 1.08), and slightly right-inclined REE distribution patterns, with higher εNd(t) value (+1.10 to +6.35). The samples show not only the marks of those within plate setting as a whole, but also those of subduction zone. Combining with the regional geological characteristic, we conclude that the Carboniferous magmatic activity in the study area generated in a within-plate setting, with variable degrees of contamination of crust during magma ascending, and probably related to mantle plume event.
Article
The late Paleozoic Bailingshan intrusions and volcanic rocks are located in the Aqishan-Yamansu arc belt in the southern part of the eastern Tianshan and are associated with an important group of iron skarn deposits. The exposed intrusive rocks are mainly granodiorite, monzonitic granite, and granite. Zircon U-Pb dating of the Tugutublak Formation tuffaceous dacitic lava yields an age of 324Ma, whereas dates of the Bailingshan granodiorite, monzonitic granite, and granite yields ages of 317Ma, 313Ma, and 307Ma, respectively. The results indicate that the Bailingshan granitoids were emplaced soon after the eruption of the Tugutublak dacite. All these rocks studied show calc-alkaline to high-K calc-alkaline and metaluminous affinities, with A/CNK values ranging 0.83-1.10. They are enriched in Rb, K, and Pb, depleted in Nb, Ta, Ti, and P, and contain low Sr/Y (4.16-23.7) and Sr (109.0-347.0 ppm) values, displaying typical arc geochemical affinities. The tuffaceous dacitic lava has low Nb/Ta (10.3-14.1) values, a wide range of Mg# (6-64), positive zircon εHf(t) (3.2-7.5) values, and elevated whole-rock εNd(t) (2.03-4.41), but low ISr values (0.70427-0.70530), indicating that the source magma may have been derived from the juvenile lower crust with minor mantle input. The Bailingshan I-type intrusions also exhibit a mixed source signal, as constrained by Nb/Ta ratios, Mg#, and isotopes characteristics. Because the granodiorite, monzonitic granite, and granite intrusions have higher zircon εHf(t) (3.3-7.5, 11.8-13.5, and 10.2-14.4, respectively) and εNd(t) (3.90, 5.78, and 5.94, respectively) values than those of the tuffaceous dacitic lava, it is suggested that mantle-derived materials may have played a more prominent role with their petrogenetic evolution. Integrating our new geological, age, geochemical and isotopic data we propose that the Aqishan-Yamansu iron skarn belt may have formed in a back-arc position or within an intra-arc basin generated by the southward subduction of the Kanggur oceanic plate beneath the Yili-Central Tianshan block during the late Paleozoic, with felsic-intermediate magmatism occurring during the basin inversion.
Article
Full-text available
The volcanic rocks of the eastern Tianshan are important for understanding the Paleozoic evolution of Paleo-Asian oceanic. It is bounded to the southern Turfan-Hami basin, and dominated by A'qikekuduke fault. Petrological, isotope chronology and geochemical features of these Carboniferous volcanic rocks show that:(1) They belong to the calc-alkaline series. There are two type of basalt: N-MORB and IAT in eastern Tianshan, which show that these volcanic rocks were formed in a back-are ocean basin tectonic environment; (2) In situ zircon U-Pb LA-ICP-MS dating on the rhyolite zircon of Di' kaner Formation yielded an age of the 320 ± 1.2Ma( MSWD = 1.3) in the southern Turfan-Hami basin. This age is explained as the intrusion age of the pluton ; (3 ) Compared with volcanic rocks of the eastern Tianshan and its neighboring areas, we find that geochemical features of the Carboniferous basalts, at similar SiO 2 levels, K 2O, K 2O + Na 2O, K 2O/Na 2O, LILE(Rb, Ba, Sr) and HFSE(Nb, Ta, Th, Zr), gradually increase from north to south, show the compositional zone. The geochemical zone is similar to the geochemical polarity in the Mesozoic and. Cenozoic circum-Pacific island arc, allow us to infer that geochemical zone can be attributed to the subduction of the Paleo-Asian oceanic plate under the Junggar- Turfan-Hami plate.
Article
A suite of pyroclastic rocks with normal sedimentary rocks, containing fragments of brachiopods and crinoids, is found along the Aqqikkuduk fault zone and its both sides in the Heilongfeng area in the northern part of the Central uplift by 1:50000 regional geological survey. SHRIMP U-Pb dating of zircons from granodiorite porphyry gravels in a conglomeratic lithic sandstone sample from this suite of rocks yields a weighted mean age of 314.0±4.2 Ma (n=9, MSWD=1.8). This age indicates that the suite of rocks is not older than 314.0±4.2 Ma and so should be assigned to the Late Carboniferous Tugutu Bulak Formation. This finding suggests that the Aqqikkuduk fault has no significance for tectonic division at lest since the Carboniferous.
Article
The stratigraphic division in the Kumtag sand-ridge, East Tianshan, has long been in dispute. During 1:50,000 regional geological and mineral survey, the conodonts Streptognathodus suberectus and Idiognathoides sinuate and the corals Pelalaxis intermedia, Lithostrotionella rarivesicula and Fomichevella kiaeri were found in two sequences of carbonate rocks in the Kumtag sand-rigde area north of the Kanggurtag deep fault, East Tianshan. The two sequences of strata are Late Carboniferous Luosuan-Dalaanian and Dalaanian-Xiaodushanian in age respectively, assigned to the Dikan'er Formation and Qishan Formation in the Karlik stratigraphic area respectively. Two suites of volcanic rocks are separated by the two sequences of sedimentary rocks. They are very easy to recognize and distinguish in the field and correlate at a regional scale because their spatial distributions are relatively fixed and the features of rock associations are distinct. Their ages are Early Carboniferous and Late Carboniferous respectively. The Qi'eshan Group can be further divided in ascending order into the Xiaorequanzi, Dikan'er, Qi'eshan and Qishan formations.
Article
The study area experienced the whole process of evolution from the passive to active continental-margin trench-arc-basin systems on the northern margin of the central Tianshan old land in the Early Cretaceous. The Aqishan-Yarnansu island-arc belt occurred on a wide continental shelf sea in the Visean Stage. The island arc has a large antiform structure, the Yamansu fault belt is a main conduit for volcanic eruption, and the forearc basin was formed in an arc-trench gap. In the early Late Carboniferous, collapse due to spreading in the back-arc area led to the formation of a synfonnal marginal basin. At the end of the Late Carboniferous, the Kanggur Ocean on the northern side closed in the form of arc-arc junction, accompanied by emplacement of granitic magma in the arc area. The early Lower Permian was a relaxation stage, when an overlapped downfaulted basin formed in the interarc area and on the southern margin of the back-arc area. In the Late Permian, the right-lateral strike-slip motion swept the whole region. Finally, right-lateral slip displacement took place between the large-scale orogenic belt and the block, thus giving rise to the initial basin-range framework as now.
Conference Paper
In this paper, we present a hybrid of graph-based and neural network modeling system of Chinese Ancient Pagoda (CAP). To implement the pagoda modeling system, we have built a basic element model library of pagoda by L system and a corresponding feature library. Feature points have been detected by our feature points extraction algorithm. After the Feature Segment Graph (FSG) is transformed into representation vectors, and these vectors are presented to the neural network which classifies them into feature classes. Once the feature information is detected, a virtual assembly process ensures the coherent architecture styles of CAP. The most important characteristic of this method is realistic modeling and rapid generating, so it can be applied to promising applications in entertainment industry.