Origin of Early Cretaceous Guandian adakitic pluton in central eastern China: partial melting of delaminated lower continental crust triggered by ridge subduction

2017 ◽  
Vol 60 (11-14) ◽  
pp. 1707-1720 ◽  
Author(s):  
Ze-Bin Luo ◽  
Shuo Xue ◽  
Li-Peng Zhang ◽  
He Li ◽  
Cong-Ying Li ◽  
...  
Keyword(s):  
Partial Melting ◽  
Continental Crust ◽  
Early Cretaceous ◽  
Eastern China ◽  
Lower Continental Crust ◽  
Ridge Subduction ◽  
Central Eastern

scholarly journals Petrogenesis of the Early Cretaceous Aolunhua Adakitic Monzogranite Porphyries, Southern Great Xing’an Range, NE China: Implication for Geodynamic Setting of Mo Mineralization

Minerals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 332
Author(s):  
Xiaohu He ◽  
Shucheng Tan ◽  
Zheng Liu ◽  
Zhongjie Bai ◽  
Xuance Wang ◽  
...  
Keyword(s):  
Partial Melting ◽  
Continental Crust ◽  
Early Cretaceous ◽  
Lower Crust ◽  
Evolutionary History ◽  
Ne China ◽  
Lower Continental Crust ◽  
Adakitic Rocks ◽  
Great Xing’An Range ◽  
Mafic Lower Crust

This paper reports on whole-rock major- and trace-elemental and Sr–Nd isotopic compositions of the Aolunhua adakitic monzogranite porphyries from the Xilamulun district in the southern Great Xing’an Range, Northeast (NE) China. The high-K calc-alkaline Aolunhua monzogranite porphyries are characterized by high Sr/Y ratios (34.59–91.02), Sr (362–809 ppm), and low Y contents (7.66–10.5 ppm), respectively. These rocks also show slightly enriched Sr and Nd isotopes ((87Sr/86Sr)i = 0.7051–0.7058; εNd(t) = −2.98–0.92), with young two-stage model ages (T2DM = 0.84–1.16 Ga). Such a signature indicates that these rocks were most likely formed by partial melting of juvenile mafic lower crust. Based on equilibrium melting and batch-melting equations, we performed incompatible trace elements modeling. Low FeOT/(FeOT + MgO) values indirectly reflect these adakitic rocks were derived from an oxidizing source related to magnesian granitoids. The decreasing content of TiO2, Fe2O3, Nb/Ta ratio, and moderately negative Eu anomalies suggest that minimal fractionation of Fe–Ti oxides and plagioclase may have occurred in their evolutionary history. The result shows that the Aolunhua adakitic porphyries and coeval adakitic intrusive rocks in this area had not experienced extensive fractional crystallization and were derived from 20%–40% partial melting of lower continental crust, which was composed of ~25%–40% and 5%–20% garnet-bearing amphibolite, respectively. Integrating with rock assemblages and regional tectonic evolutionary history in this regime, high (Sm/Yb)SN (SN—source normalized data, normalized to mafic lower continental crust with Yb = 1.5 ppm and Sm/Yb = 1.87 for continental adakite) and low YbSN ratios suggest that these rocks were generated in an extensional environment related to lithospheric delamination without crustal thickening. The collision between North China and Siberian cratons around 160 Ma blocked the westward movement of the lithosphere as a result of the subduction of Pacific plate, which then led to lithospheric delamination induced by asthenospheric upwelling and underplating. Subsequently, partial melting of mafic lower crust caused by mantle upwelling resulted in the Early Cretaceous magmatic activities of adakitic rocks and associated Mo mineralization in the southern Great Xing’an Range.

scholarly journals Petrogenesis and Tectonic Implications of the Early Cretaceous Granitic Pluton in the Sulu Orogenic Belt: The Caochang Granitic Pluton as an Example

Minerals ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 432
Author(s):  
Yuanku Meng ◽  
Zhongbo Wang ◽  
Baoping Gan ◽  
Jinqing Liu
Keyword(s):  
Partial Melting ◽  
Early Cretaceous ◽  
Large Scale ◽  
Eastern China ◽  
Orogenic Belt ◽  
Crustal Material ◽  
Granitic Pluton ◽  
Tectonic Implications ◽  
Type Granite ◽  
Sulu Orogenic Belt

The Sulu orogenic belt is the source of information on important magmatic events associated with the collision of the Yangtze craton and North China craton (NCC) and the destruction of the NCC during the Mesozoic in eastern China. In this study, we have, for the first time, identified a monzonitic granitic pluton. We hereby present petrological, geochemical, and zircon U-Pb-Hf-O isotopic data, shedding new light on the petrogenesis and tectonic implications for the granitic pluton in the Sulu belt. LA-ICP-MS and SHRIMP II analyses of zircon grains suggest that the monzonitic granitic pluton was crystallized in the Early Cretaceous (ca. 120 Ma). Geochemically, the granitic pluton shows sub-alkaline, high-K calc-alkaline, and metaluminous signatures, and is genetically of I-type granite, excluding the possibility of S-type granite, as evidenced by mantle-like zircon oxygen isotopic features. In addition, the pluton is enriched in light REE and large-ion lithophile elements (LILE) (e.g., La, Cs, Ba, K, and Pb), but depleted in high-field-strength elements (HFSE) (e.g., Nb, Ta, P, and Ti), suggesting an arc-related affinity. Zircon Hf isotopes (εHf(t) = −27.51~−32.35; TDM2 = 2979~3175 Ma) and mantle-like δ18O values (5.12–6.24‰) together indicate that the identified granitic pluton is derived from the partial melting (reworking) of the ancient mafic lower crustal material, with no supra-crustal material participation. Moreover, high Magnesium number (Mg# = 42–49) values and mafic micro-granular enclaves suggest that mantle-derived magma participated in the evolution of the granitic pluton in this study. Integrating the findings of this study and previous work, we propose that the Caochang granitic pluton is derived from the partial melting of the deep Yangtze basaltic lower crust during the Early Cretaceous, and that the large-scale thinning of the lithospheric mantle was the main factor that led to Early Cretaceous magmatic flare-up in the Sulu orogenic belt.

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