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Geoscience ›› 2018, Vol. 32 ›› Issue (02): 305-315.DOI: 10.19657/j.geoscience.1000-8527.2018.02.09

• Petrology • Previous Articles     Next Articles

Chronology,Geochemistry Characteristics and Petrogenesis of Wufenglou Lamprophyres in Northern Hebei, China

DONG Pengsheng(), DONG Guochen(), SUN Zhuanrong, LI Huawei, WANG Shushu, ZHAI Tianlei, WANG Weiqing, GENG Jianzhen   

  1. School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China
  • Received:2017-05-16 Revised:2017-12-20 Online:2018-04-10 Published:2018-05-07

Abstract:

Mesozoic lamprophyres with lithological minette are developed as dykes near Shouwangfen-Wufenglou in Yanshan region, North China Craton. Chemically, the lamprophyres are basic (SiO2 from 48.25% to 51.47%), have high values of sodium (Na2O/K2O values from 1.13 to 2.31), alkali (K2O+Na2O values from 6.61% to 7.40%), Mg# (67.84 to 71.34) and TiO2(1.31% to 1.65%), belonging to high-Ti, Na-rich calc-alkaline lamprophyres. The rock is enriched in LREE, LILE and P, depleted in HREE and HFSE (Nb, Zr, Ta), and has no Eu anomalies. LA-ICP-MS zircon U-Pb dating got an age of (135.2±1.3)Ma, indicating that the lamprophyres were intruded at the same period of magmatic activity with the nearby granitic complex at Shouwangfen area in the Early Cretaceous. The εHf(t) values of lamprophyres are ranging from -19.3 to -13.3, the two stage Hf model ages are much older than the age of diagenesis, indicating an enriched mantle source. The high values of Ba/Th (123.09 to 436.34) and Sr (915.4×10-6 to 1 257×10-6) imply the magma formation was effected by the subduction-zone fluids. The low values of Rb/Sr(0.02 to 0.11) and the high values of Ba/Rb(10.8 to 80.9) showed that the source contained amphibole. It is concluded that the lamprophyres were derived from partial melting (0.5% to 1.5%) of garnet-amphibole lherzolite of enriched mantle that formed by the interaction between sodium rich subduction fluid and mantle wedge, and the origin depth is 75 km to 100 km.

Key words: lamprophyre, chronology, geochemical characteristic, Wufenglou, Northern Hebei

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