新场地区须二段泥岩稀土元素地球化学特征及意义

Geochemical characteristics of rare earth elements and its geological signification for mudstones of the second member of Xujiahe Formation in Xinchang Area

何德军 陈洪德 钱利军

成都理工大学沉积地质研究院，四川 成都 610059

Research Institute of Sedimentary Geology, Chengdu University of Technology, Chengdu 610059, China

为了探讨川西坳陷新场地区须二段的物源、沉积环境及源区构造背景，对研究区泥岩的稀土元素（REE）地球化学特征进行了系统分析，结果表明：研究区样品的稀土元素总量较高；ω（∑LREE）/ω（∑HREE），（ω（La）/ ω（Yb））N和（ω（Ce）/ ω（Yb））N的比值表明轻重稀土分异明显；REE配分模式显示为明显的轻稀土元素（LREE）富集、重稀土元素（HREE）平坦型，Eu为明显的负异常，Ce为正常型。δCe与δEu，ω（∑REE）的相关性表明成岩作用对研究区泥岩样品的REE特征有一定的影响。δCe，δCeanom及（ω（La）/ω（Ya））n值表明研究区水体相对较浅，沉积速率较慢，属相对低能的弱氧化环境。根据稀土元素组合及其比值特征，认为研究区源岩主要为沉积岩和花岗岩；源区构造背景为活动大陆边缘。

In order to discuss the provenance, sedimentary environment and tectonic setting, the geochemical characteristics of rare earth elements for the mudstones of the second member of Xujiahe Formation in Xinchang Area of western Sichuan Depression is analyzed systematically. Results show that the amounts of rare earth elements (REE) is high in the study area. The ratios of ω(∑LREE) /ω(∑HREE), (ω(La)/ ω(Yb))N and(ω(Ce)/ ω(Yb))N show that the differentiation of (∑LREE) and (∑HREE) is obvious. The REE distribution patterns are characterized by rich in LREE, HREE is flat, Eu is evident negative anomaly and Ce is normal. The values of δCe, δCeanom and (ω(La)/ω(Ya))n show that the water is deep and the deposition rate is slow, having a low?鄄energy anoxic environment in the study area. According to the characteristics of REE and their ratios, it can be considered that the source rocks in study area are sedimentary rocks and granitic rocks. The tectonic setting is active continental margin.

10.6056/dkyqt201302006