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鲁西中生代富钾火山岩及煌斑岩微量元素和Nd—Sr同位素地球化学
引用本文:邱检生 McI.,BIA.鲁西中生代富钾火山岩及煌斑岩微量元素和Nd—Sr同位素地球化学[J].高校地质学报,1997,3(4):384-385.
作者姓名:邱检生 McI.  BIA
作者单位:南京大学地球科学系
基金项目:国家自然科学基金!49402026,地质矿产部壳幔体系组成、物质交换及动力学开放实验室研究基金
摘    要:鲁西中生代富钾火山岩产于断陷型陆相火山岩盆地中,煌斑岩多位于火山岩盘地的外圈。二者形成时代相近,产出的构造背景相同,在主量元素、微量元素和Nd-Sr同位索等特征上极为相似,均表现出富碱富钾、富轻稀土及大离于亲石元素和贫高场强元素及亲铁元素的特点,并具有显著偏低的εNd值和明显偏高的Isr值。研究结果表明,富钾火山岩和煌斑岩均起源于富集型地幔的部分熔融。

关 键 词:火山岩  富钾  煌斑岩  钕-锶  同位素地球化学
收稿时间:1997-12-20
修稿时间:1997-12-20

STUDY ON TRACE ELEMENT AND Nd-Sr ISOTOPIC GEOCHEMISTRY OF MESOZOIC POTASH-RICH VOLCANIC ROCKS AND LAMPROPHYRES IN WESTERN SHANDONG PROVINCE
Qiu Jiansheng, Wang Den,Zeng Jiahu, Brent i. A. McInnes.STUDY ON TRACE ELEMENT AND Nd-Sr ISOTOPIC GEOCHEMISTRY OF MESOZOIC POTASH-RICH VOLCANIC ROCKS AND LAMPROPHYRES IN WESTERN SHANDONG PROVINCE[J].Geological Journal of China Universities,1997,3(4):384-385.
Authors:Qiu Jiansheng  Wang Den  Zeng Jiahu  Brent i A McInnes
Institution:1. Department of Earth Sciences, Nanjing University, Nanjing, 210093, P. R. China; 2. CSIRO Division of Exploration and Mining, PO Box 136, North Ryde, NSW 2113, Australia
Abstract:The Mesozoic potash-rich volcanic rocks in western Shangdong occurred mainly in terriestrial depression volcanic basins. Their distribution were controlled obviously by deep faults, and the typical localities of them are Zouping volcanic basin, Linqu volcanic basins, and mainly distributed in two areas, one is in the vicinity of Zaozhuang, such as Xuecheng, Shagou, Tengxian etc., the other is in Xinzhuang. Both potash-rich volcanic rocks and lamprophyres were formed in early Cretaceous (Rb-Sr isochron age of potash-rich volcanic rocks in Mengyin is 119.6±3.7 Ma and K-Ar ages of lamprophyres in Zaozhuang and Xinzhuang are 125~126Ma and 113Ma respectively ). According to their mineral constitutions and chemical compositions, the lithological association of potash-rich volcanic rocks in western Shangdong belongs to a set of trachybasalt-basaltic trachyandesite-reachyandesite-latite-trachyte, of which the latite is the predominant rock type. Lamprophyres in Zaozhuang are of alkaline-rich ultramafic categories, such as cascadite, olivine and pyroxene-bearing kersantite etc., and those in xinzhuang belong to a set of alkaling-rich intermediate to basic types, such as leucite-bearing lamprophyres, kersantite and spessartite etc. Geochemical investigation shows that both potash-rich volcanic rocks and lamprophyres have similar characteristics on major elements, trace elements and Nd-Sr isotopic compositions, i.e., they are all rich in alkali, potassium, LREE and LILE, but poor in HFSE and siderophile elements, and have quit low εNd values and obviously higher Isr rations. The 87Sr/88Sr rations andεNd values of potash-rich volcanic rocks and lamprophyres are 0.71103~0.71322, -11.02~-17.54 and 0.70953~0.71109, -11.57~19.54 respectively, similar to the carbonatite in this district. Based on detailed geochemical investigations and comprehensive studies of their tectonic setting, it is concluded that both potash-rich volcanic rocks and lamprophyre in western Shangdong were originated mainly from the partial melting of enriched mantle.
Keywords:Nd - Sr isotopic compositions  enriched mantle  potash - rich volcanic rock  lamprophyre  western Shandong
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