作　　者： ; ; ; ; ; ; ;

机构地区： 中国科学院地球化学研究所矿床地球化学国家重点实验室

出　　处： 《地质学报》 2011年第3期354-365,共12页

摘　　要： 赣杭构造带金衢盆地内发育有燕山期基性脉岩,岩石类型主要为辉绿(玢)岩。K-Ar年代学研究显示基性脉岩产出时代为69.5～131.7Ma,为白垩纪岩浆活动的产物。SiO2含量范围为46.70%～50.23%,K2O+Na2O为4.01%～7.82%,可分为碱性和亚碱性岩两类。微量元素相对富集大离子亲石元素(LILE)(K、Rb、Ba)和轻稀土元素(LREE),亏损高场强元素(HFSE)(Ta、Nb、Ti)和重稀土元素(HREE)。(87Sr/86Sr)i=0.70642～0.70869,(143Nd/144Nd)i=0.512244～0.512352,εNd(t)=-2.3‰～-5.9‰,岩浆源区性质从相对亏损地幔-富集地幔分布,靠近构造带中心位置偏亏损地幔,两侧偏富集地幔。基性脉岩主要为部分熔融作用的产物,成岩过程中存在橄榄石、单斜辉石及磷灰石等矿物的分离结晶;江山安顶脉岩为斜长石堆晶产物,并伴有辉石和磷灰石的分离结晶。岩石的形成主要和部分下地壳的拆沉及玄武质岩浆底侵有关。深大断裂的重新活化及其后期控制作用对成岩影响明显。 Mesozoic mafic dykes in the Jinqu basin,Gan-Hang tectonic belt are predominantly diabases.The K-Ar dating study shows that the mafic dykes with age ranging from 69.5Ma to 131.7Ma are the result of magma intrusion during the Cretaceous Period.The SiO2 contents of 46.70% to 50.23% and K2O＋Na2O of 4.01% to 7.82% suggest that they belong to alkaline and sub-alkaline rocks.The trace elements are characterized by enrichment in LREE and LILE（K,Rb,Ba）,and depletion in HREE and HFSE（Ta,Nb,Ti）.Magma came from relative depleted mantle to enrich mantle;with（87Sr/86Sr）i=0.70642～0.70869,（143Nd/144Nd）i=0.512244～0.512352,εNd（t）=-2.3～-5.9.Source magma tends to change from relatively depleted mantle near the center of the tectonic belt to enriched mantle on both flanks of the belt.The mafic dykes mainly resulted from partial melting and fractional crystallization of olivine,clinopyroxenes,plagioclases and apatites.Mafic dykes at Anding,Jiangshan were the product of accumulation of plagioclase crystals accompanied by crystallization separation of pyroxene and apatite.The mafic dykes derived from the partial delamination of lower crust and underplating of basaltic magma in the Jinqu basin,Gan-Hang tectonic belt.Especially,reactivation of the deep fault played an important role in diagenesis of the mafic dykes.

关 键 词： 赣杭构造带 金衢盆地 基性脉岩 元素地球化学 岩石成因

领　　域： [天文地球] [天文地球]