摘要
红山子复式岩体位于西拉木伦缝合带以南、康宝-赤峰-开原断裂以北,地处白乃庙-翁牛特岛弧增生带和沽源-红山子铀成矿带北东段,由晚侏罗世早期中粗粒碱长花岗岩、粗粒斑状黑云母碱长花岗岩和早白垩世早期细粒黑云母碱长花岗岩、花岗斑岩组成。早白垩世早期细粒黑云母碱长花岗岩和花岗斑岩具有高硅贫铝、富碱高钾、高铁低钙、铝饱和温度较低的特征,A/NKC比值分别为0.99~1.03和0.93~0.98(均小于1.1),标准矿物C的含量分别为0%~0.42%和0%(均小于1%),tZr较低,分别为727~766℃和743~751℃,具有I型花岗岩的主元素特征。稀土元素总量(∑REE)较低,富集轻稀土元素,Eu负异常显著,∑REE分别为88.8~154μg/g和132~165μg/g,(La/Yb)N值分别为6.45~13.5和7.79~8.72,(La/Sm)N值分别为5.52~20.5和12.9~19.6,(Gd/Yb)N值分别为0.53~0.69和0.40~0.53,δEu值分别为0.35~0.42和0.20~0.32,稀土元素分布模式呈右倾轻稀土元素富集型;微量元素富集Rb、Th、U和K,强烈亏损Ba、Sr、P和Ti,中等亏损Nb和Ta,10000Ga/Al大于2.6,(Zr+Nb+Ce+Y)小于350μg/g,具I型花岗岩的微量元素特征,形成于非造山板内伸展构造环境。细粒黑云母碱长花岗岩和花岗斑岩的(87Sr/86Sr)i值较低(分别为0.7044~0.7054和0.7047~0.7078),εNd(t)较高(分别为-5.10^-3.99和-4.93^-2.72),铅同位素比值较低,细粒黑云母碱长花岗岩的δ18OV-SMOW值(8.60‰~11.4‰)较高,花岗斑岩的δ18OV-SMOW值(-4.6‰^-0.4‰)为负值。Sr-Nd-Pb-O同位素联合示踪显示,细粒黑云母碱长花岗岩和花岗斑岩的岩浆是中元古代源于Ⅰ型富集地幔的年轻下地壳部分熔融的产物。根据早白垩世早期细粒黑云母碱长花岗岩、花岗斑岩与晚侏罗世早期花岗岩的接触界面是I型花岗岩与A型流纹岩(或花岗岩)的化学界面,结合细粒黑云母碱长花岗岩和花岗斑岩的内、外接触带已发现铀矿化,支持细粒黑云母碱长花岗岩和花岗斑岩的内、外接触�
The Hongshanzi compound granitic body, comprising early stage Late Jurassic medium-coarse-grained alkali-feldspar, coarse-grained porphyritic biotite, early stage early Cretaceous fine-grained biotite alkali-feldspar, and granite porphyry, is part of the Caledonian period Bainaimiao-Wengniute island arc accretionary zone in the northeastern section of the Guyuan-Hongshanzi uranium metallogenic belt, the Xar-Moron suture zone, and the Kangbao-Chifeng-Kaiyuan fault zone. Geochemical study indicates that early Cretaceous fine-grained biotite alkali-feldspar and granite porphyry exhibit lower temperatures, high silicon, alkali iron, and potassium contents and low calcium and aluminum contents. They have characteristically high values of TiFeO/MgO and 10000 Ga/Al. The rare earth element (REE) composition of the fine-grained biotite alkali-feldspar and granite porphyry show high total REE contents,∑REE = 91.7–165 μg/g, seagull forms of rare earth elements,(La/Yb)N = 5.67–11.0, obvious Eu depletion, and Eu/Eu*= 0.21–0.42. The samples are enriched in Rb, Th, U and K;severely depleted in Ba, Sr, P and Ti;moderately depleted in Nb and Ta;and have a high value of Ga/Al, which is similar to chemical features of type-I granite. Isotopic geochemistry shows that the fine-grained biotite alkali-feldspar and granite porphyry have low (87Sr/86Sr)i = 0.7044–0.7078 and high εNd(t)=?5.10 – ?2.72, which indicates that they are the products of the partial melting of Mid-Mesoproterozoic young lower crust materials originating from the EMⅠ–enriched mantle under the extensional tectonic setting within the plates. Uranium mineralization hosting inner and outer contact zones of the granite porphyry support the hypothesis that uranium exploration should occur at the chemical interface of the inner and outer contact zones of the fine-grained biotite alkali-feldspar granite and granite porphyry.
作者
王常东
巫建华
张海龙
祝洪涛
杨东光
张韶华
WANG Chang-dong;WU Jian-hua;ZHANG Hai-long;ZHU Hong-tao;YANG Dong-guang;ZHANG Shao-hua(No.243 Geological Party,China National Nuclear Corporation,Chifeng 024000,China;State Key Laboratory of Nuclear Resources and Environment,East China Institute of Technology,Nanchang 330013,China)
出处
《地球化学》
CAS
CSCD
北大核心
2019年第4期356-369,共14页
Geochimica
基金
国家自然科学基金(41372071)
中国核工业集团公司项目(中核地计[2008]74号)
中国核工业地质局铀矿地勘费项目(201801)
