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江西广丰早白垩世盆地座落在124.51±11.9Ma(Rb-Sr等时线)石溪组火山岩系之上,是一个由湖进到湖退、具完整2级层序的湖相盆地;盆地湖进期沉积岩中穿插有斑岩岩脉群(正长斑岩、花岗斑岩),Rb-Sr等时线年龄为110.83±3.16Ma,U-Pb不一致曲线下交点105.4±1.3Ma,盆地最大湖面时期伴有碱性玄武岩的溢出,K-Ar年龄为100～104Ma,盆地湖退时期伴有亚碱性拉斑玄武岩溢出,K-Ar年龄为98～103Ma。同位素年代学无法区分其早晚,但野外迭置关系及沉积岩序可判别出早晚,这就构成了伴随盆地形成过程的火山-侵入杂岩活动序列,即中酸性岩脉→碱性玄武岩→拉斑岩武岩,该序列对探索该区早白垩中晚期拉张盆地的成因机制具有启迪意义。
The Early Cretaceous basin of Guangfeng in Jiangxi Province is located above the Shixi volcanic series of 124.51 ± 11.9Ma (Rb-Sr isochron) and is a lacustrine basin with a complete second-order sequence from lake to lake. The sedimentary rocks of the lake are interbedded with porphyry veins (orthorhombic and granitic porphyry). The Rb-Sr isochron age is 110.83 ± 3.16Ma and the U-Pb inconsistency curve is 105.4 ± 1.3Ma. K-Ar age ranged from 100 to 104 Ma. During the lake-level depression, subbasin tholeiite spillover occurred. The K-Ar age ranged from 98 to 103 Ma. Isotopic geochronology can not distinguish between the early and the late, but the field superposition relationship and sedimentary sequence can be identified sooner or later, which constitutes a sequence of volcanic-intrusive complexes with the basin formation process sequence, that is, acidic sodic → basic basalt → This sequence is of enlightening significance to the exploration of the genesis mechanism of the early-early Cretaceous extensional basins in the area.