摘要
在内蒙古东部好老鹿场地区1：5万区调工作中，发现了一套新的岩石组合，分别由铁镁质堆积岩、基性岩墙群、蚀变基性火山岩等组成。该套岩石组合经较强的构造破坏，呈大小不等的岩块产于本巴图组砂板岩之中。总体延伸方向呈近东西向展布，明显受区域性构造控制。岩石化学、岩石地球化学等方面的资料表明，辉石橄榄岩、辉长岩具有低Al、贫Ca和富Na的特点，MgO／（MgO＋FeO）比值为0．25，MgO含量偏低。稀土元素总量偏低，为76．03×10^-6～114．81×10^-6，轻重稀土富集不明显，分馏作用较弱。∑L／∑H为0．73～0．8，配分曲线呈平坦的“W”型，δEu=1．03～1．23，略显正异常。基性火山岩具明显的富Fe、Mg、Na，贫Al、Ti、K的特征，微量元素显示形成于洋中脊环境。同时在辉长岩中获得单颗粒锆石U-Pb年龄为362．4Ma，时代为早泥盆世晚期。其形成环境为洋中脊，属于泥盆纪古亚洲洋消减部分的残留体。
A new kind of rock association composed of mafic-cumulate rocks, the basic rock dikes and the altered basic volcanic rocks is discovered in Haolaoluchang area, eastern Inner Mongolia during the 1.50 000 regional geological survey. The rock association strongly deformed, and occurs in the sand-slate of Benbatu Formation in different shapes. The distribution of the rock masses controlled by the regional tectonic,and distributed in EW direction. The data of rock chemistry and geochemistry indicate that the pyroxene- peridotites and gabbros have low AI , Ca and MgO but high Na. MgO / （MgO＋ FeO） is about 0.25. The REE contents is low （76.03 × 10^-6～114.81 × 10^-6）,too. The enrichment of the light and heavy REE is not obvious,and the fraction is weak. ∑ L/ ∑ H = 0.73 0.8. REE normalized patterns show a flat type. δ Eu = 1.03 ～ 1.23,and Eu show weak positive abnormality. The basic volcanic rock enrich in Fe, Mg, Na, and poor in AI, Ti, K. According to the trace element, the palaeo-environment is suggested as mid-ocean ridge environment. The age of single grain zircon U-Pb of the gabbro is 362.4 Ma（early Devonian）. The new rock association formed on the mid-ocean ridge of Devonian Period. It is the oceanic crust remains of the ancient Asia on the subduction zone.
出处
《地质调查与研究》
2006年第1期21-29,共9页
Geological Survey and Research
基金
中国地质调查局区域地质调查项目(20101115002)
关键词
超基性—基性岩
洋中脊玄武岩
洋壳残片
好老鹿场
内浆古
urbasic-basic rocks
mid-ocean-ridge basalts
remains of oceanic crust
Haolaoluchang Inner Mongolia
