辽东中生代晚期和古近纪玄武岩及深源捕虏晶对岩石圈地幔性质的制约

辽东中生代晚期和古近纪玄武岩及深源捕虏晶对岩石圈地幔性质的制约

王微，许文良，纪伟强，杨德彬，裴福萍

吉林大学地球科学学院,长春 130026

收稿日期:2006-03-20 修回日期:2006-03-20 出版日期:2006-03-20 发布日期:2006-03-20

Late Mesozoic and Paleogene Basalts and Deep-Derived Xenocrystsin Eastern Liaoning Province，China：Constraintson Nature of Lithospheric Mantle

WANG Wei, XU Wen-liang, JI Wei-qiang, YANG De-bin, PEI Fu-ping,

College of Earth Sciences, Jilin University, Changchun 130061, China

Received:2006-03-20 Revised:2006-03-20 Online:2006-03-20 Published:2006-03-20

摘要/Abstract

摘要： 辽东地区玄武岩的K-Ar定年结果表明，曲家屯玄武岩形成于晚白垩世，K-Ar年龄为81．58±2．46Ma；乱石山子玄武岩形成于古近纪，K-Ar年龄为58．36±1．64Ma。本区玄武岩含有丰富的橄榄石、单斜辉石和角闪石捕虏晶。乱石山子玄武岩中橄榄石捕虏晶的Mg^#值（79．5-88．5之间，平均值为84）较曲家屯玄武岩中橄榄石捕虏晶Mg^#值（77．0～79．8之间，平均值为78．4）偏高；单斜辉石捕虏晶为透辉石，其从核部到边部的Mg^#等变化趋势与橄榄石类似；斜方辉石捕虏晶为占铜辉石，其Mg^#值介于85．2-87．6之间，平均值为86．4。捕虏晶发育的环状裂隙、扭折带、矿物成分环带以及捕虏晶与主岩Mg^#值之间的不平衡均暗示它们为玄武质岩浆上升捕获的早期岩浆晶出矿物的堆晶体。玄武岩的岩石地球化学分析结果表明：（1）它们属于碱性系列，为碱性玄武岩，曲家屯玄武岩较乱石山子玄武岩贫硅、镁，富钙、铝，它们均具有原始岩浆的特征；（2）二者具有相似的稀土元素配分模式，但曲家屯玄武岩轻稀土元素总量更高，且轻重稀土元素分离程度高；（3）二者具有相似的Sr-Nd同位素组成，Isr和εNd（t）值分别介于0．7039～0．7045和＋1．60～＋3．69，反映了亏损的岩石圈地幔特征。

Abstract: The K-Ar dating results of basahs in eastern Liaoning Province indicate that Qujiatun and Luanshishanzi basahs were formed in the Late Cretaceous with an age of 81．58 4±2．46 Ma and in the Paleogene with an age of 58．36±1．64 Ma，respectively．Abundant deep-derived xenocrysts such as olivine，clinopyroxene，and hornblende have been found in the basalts．The olivine xenocrysts from Luanshishanzi basalt have higher Mg# values (79．5-88．5，ave．84)than those from Qujiatun basalt(77．0-79．8，ave．78．4)．The clinopyroxene in basalts is diopside，whose change trend in Mg# etc．from nuclear part to periphery is similar to that of olivine．The orthopyroxene in basalts is bronzite with the Mg# values of 85．2～87．6(ave．86．4)．The circle cracks，kink bands，compositionzoning，and equilibrium of Mg# values between olivine xenocrysts and host basahs imply that the xenocrysts could be the earlier magmatic cumulate caught by the host basaltic magmas．The petrological and geochemical data of the basalts show that(1)they are alkaline basalts，but the Qujiatun basalts are higher in CaO and A12O3，lower in SiO2 and MgO than the Luanshishanzi basalts (2)they have similar REE distribution patterns，but the Qujiatun basahs have higher REE abundances and LREE／HREE ratios than the Luanshishanzi basalts；(3)they have similar Sr-Nd isotopic compositions．The Isr and εNd(t)values are 0．7039～0．7045 and+1．60～+3．69，respectively．It implies that they could be derived from the depleted lithospheric mantle．

王微，许文良，纪伟强，杨德彬，裴福萍. 辽东中生代晚期和古近纪玄武岩及深源捕虏晶对岩石圈地幔性质的制约[J]. J4.

WANG Wei, XU Wen-liang, JI Wei-qiang, YANG De-bin, PEI Fu-ping,. Late Mesozoic and Paleogene Basalts and Deep-Derived Xenocrystsin Eastern Liaoning Province，China：Constraintson Nature of Lithospheric Mantle[J]. J4.