岩浆演化过程中稀土元素分配及模拟计算——以某地英闪质火成岩体为例

本文根据稀土元素组份在固液两相体系中的分配规律,应用定量模式模拟稀土元素在岩浆体系中的分配行为,以相似性系数最大和方差最小为准则,利用计算机求解岩浆演化过程的不同参数;并以河北迁安地区英闪质侵入岩体为例进行模拟计算,其结果表明,此方法对揭示岩浆形成和演化具有意义。     

Re-Os dating of pyrite from Giant Bayan Obo REE-Nb-Fe deposit

The giant Bayan Obo REE-Nb-Fe deposit is locatedat the northern margin of the North China Block, i.e. atlatitude 41.7° north and longitude 110.0° east. The depositis very special in the world because it is the largest LREEdeposit and the second largest Nb deposit in the world,and also a large iron deposit. Geological features, mineralassemblage and geochronology of the deposit have beenreported[1—6]. However, various dating methods gave dif-ferent mineralization ages, and discrepancie…     

REE composition in scheelite and scheelite Sm-Nd dating for the Xuebaoding W-Sn-Be deposit in Sichuan

The scheelite with large size and euhedral shape from Xuebaoding, Sichuan Province is an ideal min- eral to study REE patterns and Sm-Nd dating of non-gold deposits. The scheelite has diameters of 1― 10 cm and colors of pale beige to deep orange. Most of these scheelites occur in association with beryl, cassiterite and muscovite. The rare earth elements indicate that scheelite samples from Xuebaoding W-Sn-Be deposits contain high concentrations of rare earth elements with total ΣREE Y contents in the range of 369―1725 μg·g?1 and nearly all of these scheelite samples are enriched in LREE and depleted in HREE and have negative Eu anomalies. The REE patterns of the scheelites are similar to those of A-type granite with obvious tetrad effect, similar to that of type II scheelites. Based on reported fluid inclusion studies, the mineralizing-fluid of the Xuebaoding W-Sn-Be deposit indicates low Na activity. The REE patterns of the scheelite are probably controlled by partition coefficient in hydrothermal fluid. In the 147Sm/144Nd-143Nd/144Nd diagram, the scheelites show a linear array corresponding to an isochron age of 182.0±9.2 Ma (MSWD = 0.52). The Sm-Nd age represents the formation age of the scheelite and can indicate that the W, Sn and Be mineralization at Xuebaoding took place in the Early Yanshanian. The Sm-Nd dating result is important for the study of the multi-metal resources in western Sichuan Province.     

广西姑婆山离子吸附型稀土矿床微量元素地球化学特征

探讨广西姑婆山地区离子吸附型稀土矿床中微量元素的分布与富集规律。根据野外地质特征,将矿床的风化壳从上到下分为4层。姑婆山稀土矿床为轻稀土富集型;微量元素及稀土元素整体不同程度富集;垂向上从上到下ΣLREE/ΣHREE质量分数比值逐渐减小,ΣREE呈"低→高→低"的"抛物线"式分布。部分微量元素(如Sr等)与其他微量元素之间,轻、重稀土之间,Ce和Eu与其他稀土元素之间发生了明显的分异现象。风化壳中稀土元素的迁移分异行为可能与稀土元素自身性质差异、风化壳中矿物分布、氧化还原条件、pH值、微生物活动等有关。离子吸附型稀土矿床是开放系统中多次、多阶段的地质作用的产物,其分布规律受成矿母岩和风化条件的共同控制。     

浙江缙云骨洞坑萤石矿床成矿流体特征

浙江缙云骨洞坑大型萤石矿床位于华夏古板块北东端,紧邻钦杭结合带。矿床产出于下白垩统馆头组与燕山晚期花岗岩的接触带中,矿体严格受NW向断裂控制。在系统的地质调查基础上,对其微量和稀土元素及流体包裹体开展研究。结果表明,缙云骨洞坑萤石矿轻稀土相对弱富集,重稀土相对弱亏损,具有较强的Eu负异常以及较弱的Ce负异常,配分曲线表现出典型的“V”字特征。La/Ho-Y/Ho图解表明,不同位置萤石样品表现出重结晶方向演化的趋势。Tb/Ca-Tb/La成因图解表明骨洞坑萤石矿属于热液成因类型矿床。流体包裹体测温结果表明,成矿均一温度主要在150~190℃,盐度主要在0.3%~1.5% NaCleqv,密度平均值为0.86 g/m³,成矿流体应属于中-低温、低盐度、低密度的NaCl-H₂O体系。结合地质特征认为,缙云骨洞坑萤石矿床属中低温热液裂隙充填型矿床。     

内蒙古赤峰北部林西地区中上二叠统物源研究

通过对内蒙古林西地区中上二叠统露头样品重矿物的分析研究,指出研究区内样品稳定重矿物为锆石—金红石—电气石—石榴石—赤褐铁矿—磁铁矿组合,母岩主要来自于酸性、中基性岩浆岩;基于露头样品岩矿鉴定、ZTR指数及稀土元素结果分析,指出研究区西部与东部属于不同的物源系统,西部为来自NE方向较近物源的碎屑沉积。