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铧厂沟地区碧口群玄武岩呈带状和透镜状分布于凝灰岩和凝灰质千枚岩中。在详细野外观察基础上,利用显微镜观察、主微量元素及放射性同位素分析等综合分析技术对玄武岩的岩石学、地球化学以及年代学特征进行了研究。结果表明:碧口群玄武岩普遍经历了绿片岩相的变质作用,主要矿物为斜长石、绿泥石和绿帘石;SiO_2(44.67%~49.76%)、TiO_2(1.14%~1.34%)含量较低,TFe_2O_3(12.03%~15.47%)、MgO(7.57%~9.3%)、CaO(7.29%~10.54%)含量较高。稀土总量较低,轻稀土亏损,重稀土富集。岩石微量元素和(?)石Hf同位素特征显示玄武岩形成环境可能类似N-MORB,起源于软流圈,并在上升过程中混入了古老的地壳物质。LA-ICP-MS锆石测年结果显示玄武岩的形成年龄为(316.3:±6.0)Ma(MSWD=0.78;n=7),表明碧口群火山岩系至少是两期(新元古代时期和晚古生代时期)火山作用的产物。其大规模形成时期为新元古代,后经晚古生代火山作用的叠加改造而成。
The Bachu basalts in the Huachanggou area are banded and lenticular in tuffaceous and tuffaceous phyllites. Based on detailed field observations, the petrology, geochemistry and geochronology of basalts were studied by comprehensive analysis techniques such as microscopic observation, main trace elements and radioisotope analysis. The results show that: the Bikou group basalts generally experienced metamorphism of greenschist facies, the main minerals are plagioclase, chlorite and epidote; SiO 2 (44.67% -49.76%) and TiO 2 (1.14% -1.34%) Low, TFe_2O_3 (12.03% ~ 15.47%), MgO (7.57% ~ 9.3%), CaO (7.29% ~ 10.54%) higher content. The total rare earth, light rare earth loss, heavy rare earth enrichment. The Hf isotopic characteristics of rock trace elements and? 石? Stones show that the formation of basalt may be similar to that of N-MORB, originated from the asthenosphere and mixed with the ancient crustal material during its ascent. The dating of LA-ICP-MS zircon shows that the age of basalts formation is (316.3 ± 6.0) Ma (MSWD = 0.78; n = 7), indicating that the Bikou Group volcanics are at least two phases (Neoproterozoic and Late Paleozoic) volcanism product. The formation of large-scale Neoproterozoic period, after the late Paleozoic volcanism superimposed and transformed.