黑龙江镜泊湖地区特殊类型白榴石碱玄岩的发现及其意义  

DISCOVERY OF A SPECIAL TYPE OF LEUCITE TEPHRITE IN JINGPOHU REGION OF HEILONGJIANG PROVINCE AND ITS SIGNIFICANCE

作　　者：张招崇[1] 李兆鼐[1] 李树才[2] 辛影[2] 李兆木[2] 王先政[2] 

机构地区：[1]中国地质科学院地质研究所,北京100037 [2]黑龙江省地质科学研究所,哈尔滨150036

出　　处：《地质科学》2001年第1期23-25,共3页Chinese Journal of Geology(Scientia Geologica Sinica)

基　　金：原地质矿产部项目(编号:地科专96-17)的部分成果

摘　　要：黑龙江镜泊湖西北的蛤蟆塘地区发现了一种特殊类型的白榴石碱玄岩 ,其岩石化学成分说明其为偏钠质岩石 ,并且含有钛角闪石、金云母和歪长石巨晶。其地球化学特征与离它直距只有 1 5km的“火山口森林”地区的碱性橄榄玄武岩具有明显的不同 ,白榴石碱玄岩总体上以高的 Al2 O3(1 6.73%～ 1 8.0 9% )、Na2 O(5.1 5%～ 6.36% )、K2 O(4.2 4 %～ 4.92 % )含量、强烈富集轻稀土和大离子亲石元素和低的 Mg O(4.1 9%～ 4.59% )、Ca O(5.66%～5.85% )、Mg#(0 .43～ 0 .50 )值为特征。结合其地质背景和 Sr、Nd、Pb同位素 ,认为白榴石碱玄岩是由被富含水、氟及其它挥发性组分的地幔柱物质强烈交代富集后的岩石圈地幔经低部分熔融后形成的原始岩浆在中深部经多级分离结晶后的产物。A special type of leucite tephrite is discovered in the “Frog Pool” area northwest Jingpohu region of Heilongjiang Province. Their petrochemistry indicates a weak agpaitic rock, containing the megacrysts of kaersutite, phlogopite and anorthoclase. Compared with alkali olivine basalts from the “Crater Forest” area 15 km away from “Frog Pool” , it is totally characterized by higher contents of Al 2O 3(16.73%～18.09%)、Na 2O(5.15%～6.36%)、K 2O(4.24%～4.92%) and stronger enrichment in LREE and LILE, and lower contents of MgO(4.19%～4.59%)、CaO(5.66%～5.85%)、Mg # value(0.43～0.50). The leucite tephrite is formed by the fractional crystallization in deep depth of the primitive magma which is lowly melted from the lithosphere mantle strongly metasomatized by mantle plume materials enriching in H 2O, F and other volatile components based on its geological settings and Sr, Nd Pb isotopic compositions.

关 键 词：白榴石碱玄岩 特殊类型 岩石成因 地质意义 

分 类 号：P588.145[天文地球—岩石学] P59[天文地球—地质学]