摘要
喀喇昆仑碧波潭一带下侏罗统巴工布兰莎组中新发现层状基性火山岩,岩性为强势变杏仁状玄武岩。岩石具较低的SiO2(31.4%~47.65%)和MgO(2.76%~5.28%)。相对富Na2O,为1.21%~4.44%,贫K2O,为0.17%~1.57%,Na2O>K2O,具较低Mg#,为25.31~36.96。岩石稀土总量非常高,ΣREE为562.79×10^(-6)~733.78×10^(-6),平均651.45×10^(-6)。轻重稀土元素间及重稀土元素内部分馏非常明显,具弱的负铕异常,为0.88~0.96,强烈亏损Rb,Ba,Ta和Sr,富集Th,La,Nd和Sm。地球化学特征显示,碧波潭玄武岩起源于富集地幔,原始岩浆经较低程度的部分熔融,分异程度相对较高,演化过程中可能受到一定的地壳混染作用。结合区域演化特征认为碧波潭玄武岩形成于陆内拉张环境。
The stratified basic volcanic rocks were newly discovered in the Lower Jurassic Bagong Bransha Formation in the Bibotan area,Karakoram.The lithology is strongly metamorphic almond-shaped basalt.The rocks are character-ized by low SiO2(31.4%~47.65%)and MgO(2.76%~5.28%)contents,relatively rich Na2O(1.21%~4.44%),poor K2O(0.17%~1.57%),Na2O>K2O and low Mg#(25.31~36.96)contents.The total amount of REE in the rocks is very high(ΣREE ranges from 562.79 to 733.78×10^(-6) with an average of 651.45×10^(-6)).The fractionation between the heavy and light REE elements and within the heavy REE elements is very obvious,showing a weak negative Eu anomaly(0.88~0.96),a strong deficit of Rb,Ba,Ta and Sr,and an enrichment of Th,La,Nd and Sm.Geochemical characteristics show that the Bibotan basalt originated from the enriched mantle,and the original magma underwent a relatively low de-gree of partial melting and relatively high degree of differentiation,which may have been subjected to some crustal mix-ing during the evolution process.Combined with the characteristics of regional evolution,it is considered that the Bi-botan basalt was formed in an intracontinental extensional environment.
作者
舍建忠
古力娜·太来提
冯长丽
张静
杨万志
She Jian-zhong;Gulina·tailaiti;Feng changli;Zhangjing;Yangwanzhi(Xinjiang Geology Survey Institute,Urumqi,Xinjiang,830000,China;No.1 Geological Brigade,Xinjiang Bureau of Geology and Mineral Resources,Changji,Xinjiang 831100)
出处
《新疆地质》
CAS
CSCD
2022年第2期161-167,共7页
Xinjiang Geology
基金
自治区地矿局自筹项目-新疆西昆仑岔路口地区铜镍钨锡银找矿方向研究与靶区优选资助。
关键词
喀喇昆仑
高稀土
玄武岩
地球化学特征
Karakoram
High rare earth
Basalt
Geochemical characteristics
