Petrogenesis of the Cretaceous granitoids in Zhejiang, northeast South China Block and their implications for episodic retreat and roll-back of the Paleo-Pacific Plate

2019 ◽  
Vol 132 (7-8) ◽  
pp. 1514-1536 ◽  
Author(s):  
Lu Tao ◽  
Fa-Bin Pan ◽  
Rong Liu ◽  
Chong Jin ◽  
Bao-Jian Jia ◽  
...  
Keyword(s):  
Partial Melting ◽  
South China ◽  
Basaltic Magma ◽  
Saturation Temperature ◽  
Pacific Plate ◽  
South China Block ◽  
Isotopic Compositions ◽  
Flat Slab Subduction ◽  
High Alkali ◽  
Roll Back

Abstract Two Cretaceous granitoid belts (i.e., the northwest and southeast belts) have been identified in Zhejiang, northeast South China Block. In this study, seven granitoid plutons from both the two belts were collected for zircon U-Pb dating, whole-rock geochemistry, Sr-Nd isotope, and zircon Hf isotope analyses. Chronologically, the Longyou (132 Ma), Sucun (136 Ma), Shanghekou (131 Ma), and Huangshitan (ca. 126 Ma) plutons from the northwest belt display older magma crystallization age than those of the Xiaoxiong (100 Ma), Zhujiajian (108 Ma), and Qingbang island (108 Ma) plutons from the southeast belt. The Sucun quartz monzonite and the Longyou, Shanghekou, Zhujiajian, and Qingbang island granites therein are fractionated I-type granites (i.e., partial melting of meta-igneous rocks) with relatively moderate-low Zr saturation temperature (723–823 °C) and pronouncedly evolved Nd and Hf isotopic compositions (εNd(t) = –8.17 to –5.67 and εHf(t) = –15.07 to –5.67), indicating that they are derivatives of ancient crustal melt-dominated magmas. The Huangshitan granite shows A-type granitic (i.e., granites that are alkaline and anhydrous and from anorogenic setting) features with high Ga/Al (3.47–5.58), rare earth element (REE) content (271–402 ppm), and Zr saturation temperature (781–889 °C). It holds less enriched Nd and Hf isotopic compositions (εNd(t) = –4.13 to –3.60 and εHf(t) = –5.90 to –2.16) and is attributed to partial melting of mature crustal materials with minor basaltic magma incorporation. The Xiaoxiong (quartz) syenitic porphyry is characterized by moderate SiO2 content (60.68–69.92 wt%), high alkali (9.03–11.66 wt%) and REE contents with fractionated REE pattern [(La/Yb)N = 13.8–26.1]. Its relatively depleted Nd and Hf isotopic compositions (εNd(t) = –3.67 to –3.42 and εHf(t) = –5.76 to –2.25) imply that it could be a derivative of basaltic magma from K-rich metasomatized mantle. Available geochronological data indicate that there were two episodic magmatic pulses at ca. 140–120 Ma and ca. 110–85 Ma associated with the Paleo-Pacific Plate underthrusting beneath the northeast South China Block. Here we put forward an episodic slab retreat and roll-back model to account for generation of these magmatic rocks. Firstly, the subducting Paleo-Pacific slab roll-back initiated at ca. 140 Ma and reached climax at ca. 130–120 Ma, which led to formation of the Longyou, Sucun, and Shanghekou I-type granites and the Huangshitan A-type granite, respectively. Subsequently, a flat slab subduction stage occurred with eastward trench retreat, causing a period of magmatic quiescence from ca. 120 to 110 Ma. The following second slab roll-back started at ca. 110 Ma and reached climax at ca. 100 Ma, giving rise to the earlier Zhujiajian and Qingbang island I-type granites and the later Xiaoxiong (quartz) syenitic porphyry.

scholarly journals Low-temperature thermochronology data from the eastern South China Block decipher episodic subduction of the Paleo-Pacific Plate

2021 ◽  
Author(s):  
Jinghua Wu ◽  
Huan Li ◽  
Martin Danišík ◽  
Kotaro Yonezu ◽  
Han Zheng ◽  
...  
Keyword(s):  
Low Temperature ◽  
South China ◽  
Pacific Plate ◽  
South China Block

Geochronological and geochemical results from Mesozoic basalts in southern South China Block support the flat-slab subduction model

Lithos ◽  
2012 ◽  
Vol 132-133 ◽  
pp. 127-140 ◽  
Author(s):  
Lifeng Meng ◽  
Zheng-Xiang Li ◽  
Hanlin Chen ◽  
Xian-Hua Li ◽  
Xuan-Ce Wang
Keyword(s):  
South China ◽  
South China Block ◽  
Flat Slab ◽  
Flat Slab Subduction

XKS splitting-based upper-mantle deformation in the Jiaodong Peninsula records the boundary between the North China Craton and South China Block

2020 ◽  
Vol 222 (2) ◽  
pp. 956-964
Author(s):  
Chenglong Wu ◽  
Tao Xu ◽  
Yinshuang Ai ◽  
Weiyu Dong ◽  
Long Li
Keyword(s):  
South China ◽  
North China Craton ◽  
North China ◽  
Pacific Plate ◽  
Late Triassic ◽  
South China Block ◽  
The North ◽  
Jiaodong Peninsula ◽  
Pacific Plate Subduction ◽  
Plate Subduction

SUMMARY The Jiaodong Peninsula consists of the Jiaobei massif and the Northern Sulu UHP massif. These are separated by the Wulian suture zone (WSZ), a key region for understanding the collision between the North China Craton (NCC) and South China Block (SCB). To interpret this collisional zone, a broad-band seismic profile of 20 stations was installed across the WSZ. Shear wave splitting analysis of teleseismic data revealed a contrast in the splitting patterns beneath different structural zones of the Jiaodong Peninsula. The anisotropic structures of the Jiaobei massif and Northern Sulu UHP massif can be explained by a single anisotropic layer model with WNW-ESE or E-W oriented fast directions. In the WSZ, splitting parameters exhibit pronounced variation in backazimuths indicating a two-layer anisotropy pattern. The lower layer exhibits a WNW-ESE fast direction consistent with that observed in the other two regions. Because the fast direction is generally parallel to the present-day direction of Pacific plate subduction, the anisotropy most likely represents asthenospheric return flow in the big mantle wedge caused by Pacific plate subduction. The upper layer exhibits an NE fast direction, that is, parallel to faulting associated with the WSZ. The lithosphere may preserve fossilized anisotropy induced by the Late Triassic collision of the NCC and SCB even after subsequent destruction and thinning from the Late Mesozoic to Cenozoic. We infer that the WSZ represents a lithospheric-scale structural boundary between the NCC and SCB.

Petrogenesis of the Early Palaeozoic granitoids from the Yunkai massif, South China block: implications for a tectonic transition from compression to extension during the Caledonian orogenic event

2017 ◽  
Vol 155 (8) ◽  
pp. 1776-1792 ◽  
Author(s):  
XIAO-FEI QIU ◽  
XIAO-MING ZHAO ◽  
HONG-MEI YANG ◽  
SHAN-SONG LU ◽  
TUO JIANG ◽  
...  
Keyword(s):  
Partial Melting ◽  
South China ◽  
Alkaline Rock ◽  
South China Block ◽  
Rock Series ◽  
Calc Alkaline ◽  
Tectonic Regime ◽  
Type Granite ◽  
Early Palaeozoic ◽  
T Values

AbstractA comprehensive geochronological and geochemical study was carried out on the gneissic monzogranites, porphyritic granodiorites and charnockites in the Gaozhou complex of the Yunkai massif in the southern part of the South China block to better understand the Early Palaeozoic tectonic regime of the South China block. Laser ablation – inductively coupled plasma – mass spectrometry (LA-ICP-MS) U–Pb dating of zircons indicates an age of 453.2 ± 5.1 Ma to the formation of the gneissic monzogranites, whereas the porphyritic granodiorites and charnockites were generated at 437.0 ± 1.5 Ma and 435.2 ± 2.2 Ma, respectively. The gneissic monzogranites show geochemical features consistent with the high-K, calc-alkaline rock series and are strongly peraluminous. They have SiO2contents ranging from 67.75 to 69.65 wt. % and relatively low CaO contents (1.66–1.94 wt. %). Their REE patterns are fractionated with enriched LREEs and negative Eu anomalies. The samples also show enrichment in LILEs (e.g. Rb and K) and Pb, and depletion in Sr, Ba and HFSEs (e.g. Nb, Ta, Ti and P). They haveεNd(t) values of −8.2 to −7.7. Conversely, the porphyritic granodiorites and charnockites are characterized as medium-K, calc-alkaline rock series and weakly to strongly peraluminous. They exhibit pronounced depletions in HFSEs and positive Pb anomalies. Compared to the earlier gneissic monzogranites, these rocks have relatively lower SiO2(65.50–69.36 wt. %), but higher CaO contents (3.34–4.05 wt. %), and have slightly lowerεNd(t) values (−9.1 to −8.4). Petrography and geochemical compositions of the gneissic monzogranites indicate that they are S-type granite and likely formed by partial melting of Neoproterozoic to Early Palaeozoic immature metagreywackes; whereas The porphyritic granodiorites and charnockites are A-type granite and likely derived from low degrees of partial melting of the dry, granulitic residue depleted by prior extraction of granitic melt. The new data for the Caledonian granitoids in the Yunkai massif suggest that they were formed in a post-collisional tectonic setting. They represent the earliest post-collisional alkaline magmatism reported so far in the Yunkai massif, and thus indicate a tectonic regime switch, from compression to extension, as early as the Late Ordovician to Early Silurian (~450–435 Ma).

scholarly journals Petrogenesis of Dacites in a Triassic Volcanic Arc in the South China Sea: Constraints From Whole Rock and Mineral Geochemistry

2022 ◽  
Vol 9 ◽  
Author(s):  
Wu Wei ◽  
Chuan-Zhou Liu ◽  
Ross N. Mitchell ◽  
Wen Yan
Keyword(s):  
Rare Earth ◽  
South China Sea ◽  
Rare Earth Elements ◽  
Partial Melting ◽  
South China ◽  
Volcanic Rocks ◽  
The South China Sea ◽  
South China Block ◽  
The South ◽  
T Values

Triassic volcanic rocks, including basalts and dacites, were drilled from Meiji Atoll in the South China Sea (SCS), which represents a rifted slice from the active continental margin along the Cathaysia Block. In this study, we present apatite and whole rock geochemistry of Meiji dacites to decipher their petrogenesis. Apatite geochronology yielded U-Pb ages of 204–221 Ma, which are identical to zircon U-Pb ages within uncertainty and thus corroborate the formation of the Meiji volcanic rocks during the Late Triassic. Whole rock major elements suggest that Meiji dacites mainly belong to the high-K calc-alkaline series. They display enriched patterns in light rare earth elements (LREE) and flat patterns in heavy rare earth elements (HREE). They show enrichment in large-ion lithophile elements (LILE) and negative anomalies in Eu, Sr, P, Nb, Ta, and Ti. The dacites have initial 87Sr/86Sr ratios of 0.7094–0.7113, εNd(t) values of -5.9–-5.4 and εHf(t) values of -2.9–-1.7, whereas the apatite has relatively higher initial 87Sr/86Sr ratios (0.71289–0.71968) and similar εNd(t) (-8.13–-4.56) values. The dacites have homogeneous Pb isotopes, with initial 206Pb/204Pb of 18.73–18.87, 207Pb/204Pb of 15.75–15.80, and 208Pb/204Pb of 38.97–39.17. Modeling results suggest that Meiji dacites can be generated by <40% partial melting of amphibolites containing ∼10% garnet. Therefore, we propose that the Meiji dacites were produced by partial melting of the lower continental crust beneath the South China block, triggered by the underplating of mafic magmas as a response to Paleo-Pacific (Panthalassa) subduction during the Triassic. Meiji Atoll, together with other microblocks in the SCS, were rifted from the South China block and drifted southward due to continental extension and the opening of the SCS.

Geochemical and Nd isotopic compositions of the Palaeoproterozoic metasedimentary rocks in the Kongling complex, nucleus of Yangtze craton, South China block: implications for provenance and tectonic evolution

2017 ◽  
Vol 155 (6) ◽  
pp. 1263-1276 ◽  
Author(s):  
XIAO-FEI QIU ◽  
XIAO-MING ZHAO ◽  
HONG-MEI YANG ◽  
SHAN-SONG LU ◽  
NIAN-WEN WU ◽  
...  
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
South China ◽  
Chemical Weathering ◽  
Tectonic Setting ◽  
South China Block ◽  
Yangtze Craton ◽  
Metasedimentary Rocks ◽  
Isotopic Compositions ◽  
High Pressure Granulite

AbstractPalaeoproterozic metasedimentary rocks, also referred to as khondalites, characterized by Al-rich minerals, are extensively exposed in the nucleus of the Yangtze craton, South China block. Samples of garnet–sillimanite gneiss in the khondalite suite were collected from the Kongling complex for Nd isotopic and elemental geochemical study. These rocks are characterized by variable SiO2 contents ranging from 35.71 to 58.07 wt%, and have low CaO (0.45–0.84 wt%) but high Al2O3 (18.56–29.04 wt%), Cr (174–334 ppm) and Ni (42.5–153 ppm) contents. They have high CIW (Chemical Index of Weathering) values (90.4–94.7), indicating intense chemical weathering of the source material. The samples display light rare earth elements (LREE) enrichment with negative Eu anomalies (Eu/Eu*=0.40–0.68), and have flat heavy rare earth elements (HREE) patterns. The high contents of transition elements (e.g. Cr, Ni, Sc, V) and moderately radiogenic Nd isotopic compositions suggest that the paragneisses might be those of first-cycle erosion products of predominantly mafic rocks mixing with small amounts of felsic moderately evolved Archaean crustal source. Geochemical and Nd isotopic compositions reveal that at least some of the protoliths of Kongling khondalite were sourced from local pre-existing mafic igneous rocks in a continental arc tectonic setting. Combined with documented zircon U–Pb geochronological data, we propose that the Palaeoproterozoic high-pressure granulite-facies metamorphism, rapid weathering, erosion and deposition of the khondalites in the interior of the Yangtze craton might be related to a Palaeoproterozoic collisional orogenic event during 2.1–1.9 Ga, consistent with the worldwide contemporary orogeny, implying that the Yangtze craton may have been an important component of the Palaeoprotorozoic Columbia supercontinent.

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