关键词: 含碳岩系, 稀土元素, 地球化学, 干燥缺氧环境, 非热水沉积, 勉略地区

Abstract:

The authors analyzed REE contents of the Cambrian carbonaceous rock series in the Mian-Lüe region by using ICP-MS method in order to investigate their geochemical characteristics and genetic implications. Some conclusions can be reached from the acquired analytical data：the carbonaceous rock series show narrow variation in the total contents of rare earth elements (∑REE)，from 167.88×10^-6 to 210.50×10^-6 with an average at 192.20×10^-6；the ratios of LREE/HREE vary from 6.64 to 16.25 with an average at 11.52，showing relative enrichment of LREE and depletion in HREE；the carbonaceous rock series show remarkable negative Ce anomalies， varying from 0.58 to 0.90 (0.78 on average )，suggesting that the carbonaceous rock series formed in a dry and anoxic sedimentary environment close to a marginal sea of continental slope；the carbonaceous rock series also show distinctly negative Eu anomalies, δEu_N=0.47-0.83(0.62 on average)，suggesting that they formed in a passive continental margin environment as products of normal marine sediments under low temperature(<250℃) diagenesis, consistent with the their geotectonic location in the northern margin of the Yangtze platform；according to the diagrams of La/Yb-Ce/La and La/Yb-REE，it is also confirmed that the carbonaceous rock series not formed in a hydrothermal sedimentary condition but in a normal marine condition with their main source materials coming from a continental crust with high quartz content.

Key words: carbonaceous rock series, REE, geochemistry, dry and anoxic environment, non-hydrothermal sediments, Mian-Lüe region