【摘要】：內(nèi)蒙古東烏珠穆沁旗朝不楞以西及巴潤布爾嘎斯臺地區(qū)出露一套輝長巖。LA-MC-ICPMS鋯石U-Pb測年結(jié)果顯示該輝長巖體侵位于450～461Ma,屬于晚奧陶世。樣品的Si O_2、K_2O、TiO、MgO含量低,σ=0.10～2.77,總體屬低鉀拉斑玄武質(zhì)系列。隨著Mg O含量的增加,主要氧化物如Si O_2、CaO、Fe_2O_3含量呈上升趨勢,Al2O3、Na2O呈下降趨勢。根據(jù)稀土和微量元素特征,可將輝長巖分為三類。第一類REE含量最高,具有微弱的Eu正異常,(La/Yb)_N=19.99～20.3,稀土配分曲線明顯右傾,富集LILE(Rb、Sr、Ba),相對虧損Nb、Ta。第二類REE含量減少,具有明顯的Eu負異常,(La/Yb)_N=4.88～9.68。第三類REE含量最低,具有明顯的Eu負異常,(La/Yb)_N=1.33～2.03。后兩類輝長巖均虧損Nb、Sr、Ba,富集Rb、Th、U、Zr、Hf,稀土配分曲線弱右傾,巖石形成過程中可能受到陸殼物質(zhì)混染。三類輝長巖整體兼具MORB型及島弧玄武巖特征,可能是晚奧陶世古亞洲洋向北俯沖過程中弧后盆地的產(chǎn)物。
[Abstract]:A set of zircon U-Pb dating results of gabbro. LA-MC-ICPMS indicate that the pyroxenite transgression occurred at 450 ~ 461 Ma and belongs to the late Ordovician. The content of MgO in Sio _ 2 + K _ 2O _ 2 O _ 2O _ 3 is low, 蟽 _ (0.10) ~ (2.77), which belongs to the Black Tortoise series of low K _ 2O _ 3. With the increase of MgO content, the content of main oxides such as Sio _ 2CaO _ 2O _ 2 Fe _ 2O _ 3 increases and Al _ 2O _ 3H _ 2O decreases. According to the characteristics of rare earth elements and trace elements, gabbro can be divided into three types. The first kind of REE has the highest content and weak EU positive anomaly, (La/Yb) tipped to the right of the partition curve of rare earth elements, enriched in LILE (RB ~ (2 +) S ~ (2 +) Ba), and relatively depleted in NB ~ (2 +) Ta. In the second group, the content of REE decreased and there was obvious negative EU anomaly, (La/Yb) was 4.88% 9.68%. The content of REE in the third group was the lowest, with obvious EU negative anomaly, and (La/Yb) was 1.332.03. The latter two types of gabbro are depleted in NB, Sr and Ba, enriched in RbTH, UZR and HF, and the REE partition curve is weakly right tilted, which may be contaminated by continental crust materials during the formation of the rocks. The three types of gabbro have the characteristics of MORB type and island arc basalt, which may be the product of the back-arc basin during the northward subduction of the Paleo-Asian Ocean in late Ordovician.
【作者單位】： 中國地質(zhì)大學(xué)(北京)地球科學(xué)與資源學(xué)院;四川理工學(xué)院經(jīng)濟與管理學(xué)院;河北省區(qū)域地質(zhì)礦產(chǎn)調(diào)查研究所;四川省地質(zhì)工程勘察院;
【基金】：中國地質(zhì)調(diào)查局地質(zhì)調(diào)查項目(編號:1212010811001、1212011085490、12120114093901、1212011220465)的成果~~
【分類號】：P588.124

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