摘要
分布于甘肃省榆中县兴隆山地区的兴隆山岩群为一套浅变质火山岩与浅变质碎屑岩所组成的岩石组合,其火山岩主要出露于兴隆山岩群中岩组和上岩组。兴隆山岩群火山岩岩性主要为变质玄武岩,具有低w(K2O)、w(Na2O+K2O)和w(TiO2)的特点,且w(TiO2)和w(P2O5)接近于洋中脊玄武岩的平均质量分数,为亚碱性的拉斑玄武岩系列,火山岩稀土元素总量低,轻、重稀土元素分馏不明显,稀土元素配分曲线为轻稀土元素略亏损、重稀土元素平坦型,与洋中脊玄武岩的配分曲线类似,火山岩大离子亲石元素相对富集,高场强元素和重稀土元素平坦,稀土元素、微量元素特征及构造环境判别显示兴隆山岩群的火山岩形成于中元古代秦祁昆多岛洋中部略富集的E型洋中脊的海底扩张环境。
The Xinglongshan Group exposed in the Yuzhong area, Gansu Province is a sequence of slightly metamorphosed volcano-sedimentary rocks. They mainly occur in the middle and upper formations of the Xinglongshan Group, and their lithology is dominated by meta-basalt. The Xinlongshan meta-basalts have low w（K2O）, w（Na2O＋K2O） and w（TiO2） contents, with w （TiO2）/w （P2O5） ratio close to that of average mid-ocean ridge basalts, which characterize sub-alkaline tholeiitic baslt. With low REE abundances, they show no significant light/heavy REE fractionation, with slightly depleted light REE and flat heavy REE distribution, which resemble those of mid-ocean ridge basalts. Large ion lithophile elements are relatively enriched, while high filed strength elements and heavy REE show flat distribution patterns. Collectively, REE, trace element and tectonic setting discrimination indicate that the Xinglongshan volcanic rocks are formed in a E-type mid-ocean spreading center located in the middle part of the Qin-Qi-Kun Ocean.
出处
《地质科技情报》
CAS
CSCD
北大核心
2007年第2期45-50,共6页
Geological Science and Technology Information
基金
中国地质调查局项目"临夏市幅(I48C001001)
定西县幅项目(I48C001002)
1:25万数字区域地质调查"项目(200413000007)
关键词
兴隆山岩群
火山岩
构造环境
洋中脊玄武岩
甘肃省
Xinglongshan Group
volcanic rock
tectonic setting
mid-ocean ridge basalt
Gansu Province
