Magma type and genesis of the basic-ultrabasic layered intrusions in Panzhihua-Xichang area,Southwest China

The layered intrusions in the Panzhihua-Xichang area may be grouped into two types: basic rock masses represented by the Panzhihua rockbody and basic-ultrabasic rock masses represented by the Hongge rockbody. Their major difference lies in that the former has poorly developed ultramafic facies, while the latter is characterized by well developed mafic facies and ultramafic facies. There exists apparent rhythmic stratification in the rock masses, which can be basically divided into four grades in terms of superimposition relationship and multicycle characters. Both direct and indirect evidence suggest that the magma responsible for the layered intrusions in this area should be a transition-type alkaline olivine basalt magma derived directly from partial melting of the upper mantle. In rhythmic cycles of various grades, the magmatic evolution is characterized obviously by periodicity and early enrichment of Fe and Ti, which is evidently different from the evolution of the Skaergaard magma in which Fe and Ti are enriched at the late stage. The FCA diagram can be used to describe the unique evolutionary trend of magma in this area. It is demonstrated in this diagram that the enrichment of Fe and Ti is consistent with the increase of basicity. In the upper magmatic chamber, the evolutionary trend of magma is conditioned by the difference in pressure, and this enables magma to form different types of rock assemblage. In the Fo-Di-An system, when the pressure exceeds 5 x 18⁸ Pa, forsterite is incompatible with anorthite, and the rock facies sequence of Hongge type might form; when the pressure is lower than 5 x 10⁸ Pa, forsterite can coexist with anorthite, and the rock facies sequence of Panzhihua type is likely to form if the magma is relatively rich in Mg and Fe components.     

Rare—Earth Element Geochemistry of Elogites from the Ultra—High Pressure Metamorphic Belt in Central China

Based on their REE contents and REE patterns,eclogites from the ultra-high pressure metamorphic belt in central China may be roughly divided into xis types including LREE-rich.LREE-rich positive Eu anomaly,LREE-rich negative Eu anomaly,REE pattern-smooth,MREE-rich and HREE-rich.The LREE_rich,LREE-rich positive Eu anomaly and LREE-rich negative Eu anomaly types of eclogites are dominant .REE types of eclogites in different areas can be compared and the REE feactures of the same REE type of eclogites in different areas are similar.The results of reconstruction of the primary rocks show that the primary rocks of eclogites possibly are dominated by continental tholeiites which are the product of partial melting of relatively fertile mantle and the rocks of tholeiite crystallization-differentiation.There is perfect evolution relationship among the primary rocks of the LREE-rich, LREE-rich positive Eu anomaly and LREE-rich negative Eu anomaly types of eclogites and among those of the REE pattern smooth and MREE-rich types of eclogites,the former three types were deried from continental settings and the latter two from nearly oceanic settings.Meanwhile,it is concluded that the mantle sources of primary rocks of the eclogites are inhomogeneous and the primary rocks of eclogites in this area appear to have undergone varying degree of crustal contamination.     

东胜煤田北部延安组沉积体系及聚煤特征

鄂尔多斯盆地延安组在全盆地发育,是盆地内最重要的含煤、油、气地层之一,依据大量的钻井、测井资料,运用沉积学的方法,对东胜煤田艾来五库沟-台吉召延安组沉积体系及聚煤特征进行了分析。研究认为延安组为辫状河、曲流河及辫状河三角洲沉积,沉积微相主要发育有辫状河体系的河床滞留沉积及心滩、河漫滩和河漫沼泽沉积;曲流河体系的河床滞留沉积、边滩、天然堤、河漫滩、河漫沼泽和河漫湖泊沉积;辫状河三角洲体系的分支河道、天然堤和河漫沼泽沉积等。辫状河及曲流河垂向上表现为下粗上细的间断性正韵律或正旋回,为典型的河流二元结构特征。聚煤特征分析认为,辫状河和曲流河体系河漫沼泽环境是有利成煤场所,由于河道的冲刷、下切作用,辫状河道和曲流河道形成的煤层厚度较小、侧向连续性差;三角洲体系的三角洲平原是有利的成煤带,其煤层具有厚度较大、结构较为简单、分布范围较广、连续性较好的特征。     

天然钛榴石的穆斯堡尔谱及晶体化学分析

本文收集了一组钛榴石样品,作了穆斯堡尔谱和化学分析。采用各对应双峰等值限制拟合。拟合结果,统计误差X~2均较小。文中还分析了钛榴石结构的阳离子占位情况,并对其五对双峰谱指派如下:Fe~(3+)在[Y]位和(Z)位,Fe~(2+)在{X}和[Y]位,而另一对双峰指派为Fe~(2+){X}→Fe~(3+)(Z)的电荷离域。从化学分析和穆斯堡尔谱数据求出二种方法Fe~(2+)/∑Fe的差值,说明钛榴石中有Ti~(3+)的存在,用此简便方法估算了Ti~(3+)的含量,得出了四面体中阳离子的占位择优为Fe~(3+)>(Al~(3+),Ti~(4+))的结论。     

新矿物—盈江铀矿

新矿物产于云南盈江县的一个铀矿点氧化带,与多种铀矿物共生。该矿物为致密状集合体,黄色,透明至半透明。斜方晶系,空间群C222_1,晶胞参数a=13.73(1),b=15.99(1),c=17.33(2);V=3804(5);Z=8。计算比重4.17。二轴晶负光性,2V计算=83°,α=1.669;β=1.692;γ=1.710。紫外光照射发弱绿黄色荧光。化学成分UO_376.54,P_2O_511.10,K_2O 2.46,CaO 1.57,ThO 0.51,RE_2O_3 0.45,H_2O 7.37%。矿物化学式为(K_(1-x),Ca_x)(UO_2)_3 (PO_4)_2 (OH)_(1+x)·4H_2O,文中还给出X射线粉晶衍射数据。     

蚀变超基性岩金（镍）矿床中的贵金属元素──以云南墨江金矿和陕西煎茶岭金矿为例

云南墨江金矿和陕西煎茶岭金矿中Ａｇ、Ａｕ和ＰＧＥ（铂族元素）的丰度和共生状况如下：（１）两矿床中的Ａｇ－Ａｕ关系呈三种情况：硅质岩型矿石和其他类型低品位金矿石中Ａｇ－Ａｕ基本上不具相关关系；石英脉型矿石中Ａｇ－Ａｕ呈明显的正相关关系；氧化矿石中Ａｇ－Ａｕ呈负相关关系。（２）所有样品中的ＰＧＥ均低于７１×１０（－６），其ＰＧＥ的特征是Ｐｔ≥Ｐｄ和Ｒｕ＞Ｏｓ、Ｉｒ、Ｒｈ。（３）这些样品的地幔标准化ＰＧＥ分布模式是以Ｒｈ为峰的上凸曲线，而墨江样品又具Ｉｒ的负异常。与一般超基性岩的情况不同，这些样品的模式曲线中Ｐｄ－Ａｕ部分呈陡弯折，它表明矿化元素金可能主要由区域成矿流体提供。     

广西宜州裂陷槽晚古生代演化与早石炭世沉积锰矿分布*

滇黔桂地区晚古生代浅水碳酸盐岩台地与深水硅泥质盆地共存的古地理格局,是在加里东期褶皱基底上发生裂陷及差异沉降而发展起来的。广西宜州—柳州一带既是晚古生代上扬子碳酸盐岩地台南缘1条重要的沉积相分界线,也是晚古生代桂中和桂北地层分区、古生代—中生代雪峰山南段构造体系和桂中坳陷构造体系的分界线。文中通过对宜山—柳州一带晚古生代地层的区域对比和成因分析,恢复了桂中宜山—柳州地区晚古生代沉积盆地的演化历史。狭长型宜州裂陷槽盆地西起丹池断裂,向东经龙头、北牙、宜州延伸至柳州。自中泥盆世开始,首先在东西两端开始裂陷下沉,至早石炭世发展成型。受北侧来自江南隆起带陆源碎屑物质充填影响,其表现为南北不对称并在早石炭世晚期被填平。在宜州裂陷槽内发育多处早石炭世沉积型碳酸锰矿,含矿地层分布、地层序列及其沉积背景明显与裂陷槽演化有关。它们既是盆地演化历史的见证,也体现了桂中地区裂陷海槽的特色,值得在后续锰矿成因研究中予以重视。     

酸雨对桂林枯水期岩溶地下水δ13CDIC及碳汇效应的影响

定量评价硫酸对岩溶碳汇效应的影响有助于提高岩石风化碳汇通量估算精度, 对当前全球气候变化研究意义重大.选取受酸雨影响的桂林岩溶区为研究对象, 在枯水期对研究区14个岩溶大泉和15条地下河水化学成分和碳同位素进行了测试分析, 结果表明: 岩溶大泉和地下河中阳离子以Mg2+和Ca2+为主, 阴离子以HCO₃-为主, 分别占阳离子和阴离子组成的90%以上, SO₄2-含量较低, 其含量范围为0.004~0.213mmol/L; 所占阴离子组成比例为0.12%~6.11%;δ13C_DIC、[Ca2++Mg2+]/[HCO₃-]更偏向于碳酸溶解端元, 离硫酸溶解端元距离远, 证实硫酸参与碳酸盐岩的溶解对地下水无机碳(dissolved inorganic carbon, 简称DIC)及δ13C_DIC的影响有限; 与Sr2+/Ca2+值一样, δ13C_DIC主要受径流条件控制, 其大小可以反映地下水径流条件的强弱.利用化学计量关系计算出由硫酸溶蚀碳酸盐岩的平均比例为22.64%, 产生的DIC(HCO₃-_H2SO4)占总DIC的平均比例为13.04%, 碳酸产生的DIC(HCO₃-_H2CO3)占地下水总DIC的比例为86.96%, 其中来源于土壤大气中的HCO₃-比例为43.48%.因此, 扣除硫酸对地下水中DIC的贡献后, 岩溶碳汇效应将减少13.04%.      

下扬子区二叠系层序地层的地球化学特征

本文以安徽巢县平顶山、鬼门关剖面为例，阐述了二叠系沉岩的主要岩石类型，即灰岩、硅质岩和泥质岩的岩石学特征及稀土元素组成特点；划分出七种沉积相类型，即局限台地相、开阔台地相、斜坡相、盆地相、三角洲相、汪 相和陆缘泻湖相；识别出七个Ⅲ级层序，其中四个为Ⅰ型层，三个为Ⅱ型层序。对栖霞组灰岩的地球化学测试数据进行了统计分析，总结了海侵体系域，高水位体系域的氧碳同位素、稀土元素和微量元素组成的差异，并认为造