南苏鲁超高压变质带东海地区富钛榴辉岩及金红石矿的成因  

Origin of Ti-rich eclogite and rutile deposit in the Donghai area of the southern Sulu UHP metamorphic belt, China

作　　者：王大志 张泽明[2] 沈昆 赵旭东[2] 

机构地区：[1]江苏省地勘局第六地质大队,江苏连云港222300 [2]中国地质科学院地质研究所,北京100037 [3]山东省地质科学研究院,山东济南250013

出　　处：《地质通报》2006年第7期839-849,共11页Geological Bulletin of China

基　　金：国家重点基础研究发展规划(973)项目(2003CB716501);国家自然科学基金项目(40399142和40472036)资助。

摘　　要：苏鲁超高压变质带南部的东海地区有富Fe-Ti的钛铁矿榴辉岩和富Ti的金红石榴辉岩。富Fe-Ti榴辉岩的次要矿物主要由钛铁矿和钛磁铁矿组成,可含少量金红石,具有很低的SiO2(38.0%～42.3%)、Na2O+K2O(0.48%～2.13%)和Zr、Nb、Ta、Ba、Rb、REE含量,很高的FeO(18.24%～25.33%)、V和Co含量,并具有不同程度的LREE亏损、明显的正Eu异常;富Ti金红石榴辉岩含有丰富的金红石和磷灰石,SiO2含量范围(38.0%～54.8%)较宽,FeO含量较低,P2O5含量较高(可达4.1%),而且TiO2与P2O5含量具正相关性。相对于原始地幔岩,富Ti金红石榴辉岩具有Rb、Th、K、Nb、Pr、Nd、Eu、Ti、Lu的负异常和Ba、Sr、Zr的正异常,并具相对较高的REE含量,LREE富集和HREE亏损的REE分配型式。岩石学和地球化学特征揭示,Fe-Ti榴辉岩的原岩是变质的Fe-Ti辉长岩,是基性岩浆强烈分离结晶作用形成的超基性—基性—中酸性层状侵入体的特征组成部分。Ti-rich eclogites in the southern Sulu ultrahigh-pressure （UHP） metamorphic belt may be divided into two types： Fe- and Ti-rich ilmenite eclogite and Ti-rich rutile eclogite. The Fe-Ti eclogites contain abundant ilmenite and Ti-magnetite with minor futile and have very low SiO2 （38.0-42.3%）, Na2O＋K2O （0.48-2.13%）, Zr, Nb, Ta, Ba, Rb and total REE contents but relatively high total FeO （18.24-25.33%）, V and Co contents. Their REE patterns are characterized by more or less depletion of LREE and pronounced positive Eu anomalies. The Ti-rich ruffle eclogites have abundant rutfle and apatite and show a wide range of SiO2 （38.0-54.8%） and relatively low FeO and high P2O5 contents （up to 4.1%）; moreover, their TiO2 contents are positively correlated with P205 contents. Primitive mande-normalized trace element patterns of the ruffle eclogites show negative anomalies of Rb, Th, K, Nb, Pr, Nd, Eu, Ti and Lu and positive anomalies of Ba, Sr and Zr. In addition, the ruffle eclogites have relatively high REE contents and LREE-enriched and HREE-depleted patterns. The petrological and geochemical characteristics mentioned above indicate that the protoliths of Fe-Ti eclogites were Fe-Ti gabbros in a layered ultramafic to mafic intrusion formed by intensive fractional crystallization of basaltic magma.

关 键 词：金红石榴辉岩 Fe—Ti榴辉岩 超高压变质作用 苏北东海地区 

分 类 号：P588.3[天文地球—岩石学] P618.47[天文地球—地质学]