Voluminous felsic rocks (mainly monzonitic) and coeval mafic rocks (mainly monzogabbro–diorites) were emplaced in the Taihang–Yanshan orogen of eastern North China craton in Mesozoic time. The monzogabbro–diorites have high Sr (mostly >1300 ppm) and low e Nd (t) values (−9.5 to −15), indicating a long-term incompatible element enriched subcontinental lithospheric mantle source for their genesis. The monzonitic rocks show elemental geochemistry (e.g. high Sr, and REE patterns) and isotopic compositions similar to the monzogabbro–diorites, which leaves little doubt that the two rock suites share a similar origin. These mafic and felsic rocks thus represent a significant addition of juvenile continental crust from an enriched lithospheric mantle source in the Mesozoic, and their generation via melting of enriched portions of the subcontinental lithospheric mantle is probably an important mechanism responsible for the lithosphere thinning beneath eastern North China craton.

Sr–Nd isotopic characteristics of the Mesozoic magmatism in the Taihang–Yanshan orogen, North China craton, and implications for Archaean lithosphere thinning

Nd isotopic variation of Paleozoic-Mesozoic granitoids from the Da Hinggan Mountains and adjacent areas, NE Asia: Implications for the architecture and growth of continental crust

High Sr/Y magmas generated through crystal fractionation: Evidence from Mesozoic volcanic rocks in the northern Taihang orogen, North China Craton

Mesozoic magmatism and metallogenesis associated with the destruction of the North China Craton: Evidence from U–Pb geochronology and stable isotope geochemistry of the Mujicun porphyry Cu–Mo deposit

Geochemical and isotopic imprints of early cretaceous mafic and felsic dyke suites track lithosphere-asthenosphere interaction and craton destruction in the North China Craton

The Wanganzhen complex is one of representative example of Taihang-Da Hinggan tectonomagmatic belt in eastern China, which as the largest scale adn the most rock types. It consists of three-stage rocks. According to the major element, trace element, REE and ND, SR, PB isotopic characteristics of the Wanganzhen complex reported in this paper, the main stage rocks (Granodiorite, adamellite, and few quartz diorite) have similar petrological and geochemical characteristics to those of adakite with SiO₂≥58%, Al₂O₃≥15%, low Y content (4.20~12.68μg/g), high SR content (518~861μg/g) and Sr/Y ratios (60.19~178.10), LREE enrichment with (La/Yb)N=34.06~76.91, HREE depletion with Yb=.044~1.00, no obviously Eu anomaly (Eu/Eu*=0.83~1.03), and relative depletion in the high field strength elements (such as Nb, Hf, Ti), I(Sr)=0.7060, negative eNd(t) value (-16.29~-14.27) and positive eSr(t) value (+23.7~+25.0), but obviously different from those of subduction-related adakites. These adakite-like rocks were most likely derived from the partial melting of basaltic lower crust in the thickened crust resulted from hot mantle material upwellins as several mushroom cloud and the thermally altered ground uplifting to the bottom of continental crust during late Jurassic period. But the early and the late stage ones belong to non-adakites. The early basic- to intermediate- instrusive rocks (hornblendite, gabbroite and diorite) are high Mg and Fe, LREE enrichment, EU positive anomaly, enriched in compatible elements and low incompatible elements, I(Sr)=0.7056, eNd(t)=-16.72~-10.92, which are the products of partial melting of subcontinental lithospheric enrich mantle and probably represent the underplating basaltic magma below the thickened continental crust during early Mesozoic era. The late alkaline intermediate to acid-intrusive rocks (alkali-granite, quartz syenite and quartz monzonite) are characteristic of high K and Na alkaline series and high ΣREE, negative Eu anomaly, low Sr content, high Y and Yb, negative Sr anomaly, I(Sr)=0.7062, eNd(t)=-16.25, suggesting that the formation of adakite-like rocks of the main stage result in the lithospheric delamination and cause asthenosphere to upwell to the bottom of thinned continental crust, so the rocks of the late stage are formed by the partial melting of the materials in the crust-mantle transformation belt even in the middle crust. In this paper the Rb-Sr isochronal age of granodiorite (145.7±5.3Ma) is reported. Based on the Rb-Sr isochronal age of granite and granidiorite, the main body of the Wanganzhen complex was probably formed in late Jurrasic period between 137.8Ma and 145.6Ma.

HongXiang Shao

Papers

Petrological and geochemical characteristics of the Wanganzhen complex and discussion on its genesis.