Abstract
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.
Highlights
The Sulu orogenic belt is an ideal place for studying continental deep subduction and the crust–mantle interaction [1,2,3,4,5,6,7]
Combined with above geochemical features, we tentatively argue that the Caochang granitic pluton is most probably a result of the partial melting of crustal material; detailed petrogenetic process of the granitic pluton and deep insights are addressed below
Cretaceous granites originated from partial melting of normal crustal material rather than and geochemical characteristics of early Cretaceous granites, we argue that early Cretaceous granites thickened crust in the Sulu belt
Summary
The Sulu orogenic belt is an ideal place for studying continental deep subduction and the crust–mantle interaction [1,2,3,4,5,6,7]. Multiple studies have reported that the Sulu orogenic belt experienced two stages of evolution, namely the deep-subduction stage and the subsequent exhumation stage [4,8,9]. Cretaceous granitoid rocks (130–110 Ma), which are widely distributed throughout the Sulu orogenic. Competing models were proposed to explain the petrogenesis of the Early Cretaceous granitoid rocks in the Sulu belt [16,17,18,19,20].
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