Early Mesozoic thrust tectonics of the northwest Zhejiang region (Southeast China)

Abstract

The NW Zhejiang region of South China occupies a key tectonic position near the suture zone of the Yangtze and Cathaysian blocks and is of critical importance for the assembly of East Asia. Sedimentological and tectonic analyses indicate that the region had a SE-dipping paleoslope in the late Paleozoic to Early Triassic. A transitional sedimentary environment from deep sea to continental molasse is documented in the early Triassiclate Triassic interval. Associated structures are NW-vergent folds and thrusts that root southeastward beneath the high-grade Chencai metamorphic complex. The structural styles of this foreland fold-and-thrust belt are characterized by multifold duplexes and individual folds that are together zoned from SE to NW as follows: (1) core zone characterized by shear folds and ductile thrusts; (2) SE belt with out-of-sequence thrusting of multifold duplexes and an average shortening of 50%; (3) central belt with duplexes, imbricate fans, and an average shortening of 40%; and (4) NW belt with Jura-type folds and a shortening of ~10%. A tectonic model for the foreland fold-and-thrust belt is discussed in relation to the early Mesozoic archipelago paleogeography of South China.

Geochronological, geochemical and Nd–Hf–Os isotopic fingerprinting of an early Neoproterozoic arc–back-arc system in South China and its accretionary assembly along the margin of Rodinia

“…09WG-53A is metadiabase taken from Shitun (Zhenghe in Fujian) in the Wuyi Domain. It, together with the lensoid metagabbro and ultramafic rocks, has been previously proposed as members of early Paleozoic or early Mesozoic "Zhenghe ophiolitic mélange" (Guo et al, 1989;Xiao and He, 2005). The grains are mostly subhedral or crystal fragments and CL images reveal a weakly oscillatory internal zonation with low to variable luminescence (Fig.…”

“…In the Shitun area in the Wuyi domain, there is a maficultramafic complex that has previously been described as an "ophiolitic mélange" (e.g., Xiao and He, 2005 (Fig. 11b and c), these serpentinites plot in the fields of residual peridotite and of lithospheric mantle, respectively, suggesting that the serpentinites can be interpreted as part of an ophiolite suite.…”

Indosinian isotope ages of plutons and deposits in southwestern Miaoershan-Yuechengling, northeastern Guangxi and implications on Indosinian mineralization in South China

“…Felsic melts resulting from the melting of the South China base triggered by the Indosinian orogeny could Luxi complex in southern Jingxi-northern Guangdong 239 ± 5 Ma (zircon LA-ICP-MS) [55] Xiazhuang complex in southern Jingxi-northern Guangdong 236 ± 8 Ma (zircon LA-ICP-MS) [55] Exiantang Sn-deposit in Jingxi 231.4 ± 2.4 Ma (muscovite 40 Ar/ 39 Ar plateau age) [56] Wuliting intrusion in Daji Mountain, Jingxi 238.9 ± 1.5 Ma (zircon SHRIMP U-Pb) [57] Baimianshi granite in Jingxi 249.9 ± 1.3 Ma (Rb-Sr isochron) [58] Darongshan intrusion in southeastern Guangxi 233 ± 5 Ma (zircon SHRIMP) [59] Jiuzhou intrusion in southeastern Guangxi 230 ± 4 Ma (zircon SHRIMP) [59] Taima intrusion in southeastern Guangxi 236 ± 4 Ma (zircon SHRIMP) [59] Limu deposit in northeast Guangxi 214.1 ± 1.9 Ma (muscovite 40 Ar/ 39 Ar) [60] Miaoershan-Yuechengling batholith in northeastern Guangxi 243.0 ± 5. Hehuaping Sn deposit in southern Hunan 224 ± 1.9 Ma (molybdenite Re-Os isochron) [61] Weishan monzonitic granite in Hunan 244 ± 4 Ma (zircon SHRIMP) [62] Guandimiao intrusion in Hunan 239 ± 3 Ma (zircon SHRIMP) [62] Granite from the Baima Mountain in Hunan 243 ± 3 Ma (zircon SHRIMP) [62] Longyuaba intrusion in southern Jingxi-northern Guangdong 241.0 ± 5.9 Ma, 241.0 ± 1.3 Ma, 210.9 ± 3.8 Ma (zircon LA-ICP-MS) [63] Granite in the eastern Zhuguangshan 204 to 235 Ma (zircon SHRIMP) [58] Xiazhuang granitoid in northern Guangdong 228.0 ± 0.5 Ma (zircon SHRIMP) [58] Syenite in southwestern Fujian 252 to 242 Ma (zircon SHRIMP) [64] Topaz bearing granite in western Fujian 226 Ma (zircon SHRIMP) [65] Hexi group plagioclase amphibolites in Jingning, Zhejiang 252 ± 5 Ma (metamorphic zircon SHRIMP) [66] Basic-ultrabasic rock in southwestern Zhejiang Metamorphic event at 251 to 233 Ma [67] Nappe structure in Zhejiang (P 3 -T 1 ) [68] Taiwan Metamorphism at 260 to 240 Ma [69] Syenite in Hainan 244 ± 7 Ma (zircon SHRIMP ) [70] have exsolved volatile phases during the ascending and crystallization of the melts such as those of the Yanshanian granite. Once these volatile phases exsolved from the felsic melts the rare metals and REE will participate into the volatile phase, which favors the formation of the Indosinian granitoid related deposits.…”

Triassic 40Ar/39Ar ages from the Sakaigawa unit, Kii Peninsula, Japan: implications for possible merger of the Central Asian Orogenic Belt with large-scale tectonic systems of the East Asian margin

“…A peculiar feature of the craton is the ca. 1300 km-wide South China Indosinian Orogen that occupies its southeastern half (Xiao and He 2005;Li and Li 2007, and references therein). The southeastern part of the craton, the Cathaysia block, contains an extensive belt of granitoids that has been interpreted as a continental margin magmatic arc within which a granitic belt of Mesozoic and possibly Palaeozoic age was generated due to northwestward subduction of oceanic lithosphere (Jahn et al 1976;Li et al 2006).…”

“…A wide area of the southeastern part of South China craton is affected by magmatism, metamorphism and deformation in this period (e.g. Faure et al 1998;Li 1998;Xiao and He 2005;Li and Li 2007). Also in Indochina magmatism, (ultra) high-temperature metamorphism and ductile deformation occurred in the 260-240 Ma time span (Lepvrier et al 2004).…”