华南西部土壤Cd、Pb地球化学基线研究及评价

在华南西部的右江河谷地区按照10 km×3 km的网度采集71个浅层土壤样品,分析测试样品中Cd和Pb的含量,应用累积频率法和分形分析方法分析计算其环境地球化学基线值,以此为评价标准对本地区浅层土壤的Cd、Pb污染进行评价。结果表明:2种分析计算方法所得到的环境地球化学基线值相差不大,其中Cd的基线上限相差10.3%,基线值相差9.4%,Pb的基线上限相差3.6%,基线值相差6.7%,说明2种方法的计算结果都合理,本文取2种方法的算术平均值作为其环境地球化学基线值,即Pb为25.44 mg/kg,Cd为0.304 mg/kg。Cd的单因子污染评价结果显示轻度污染占67.61%、中度污染占23.94%、重度污染占5.63%,Pb的单因子污染评价显示轻度污染占53.52%、中度污染占25.35%、重度污染占11.27%;内梅罗综合污染评价显示轻度污染占52.11%、中度污染占33.88%、重度污染占8.45%,显示出本区以轻度污染为主,中度污染次之,少数地区达到了重度污染,且中、重度污染区主要分布在研究区东南部和西北部,在中西部地区有一个中度污染点。大多数样品Cd和Pb的地累积指数小于1,说明本区Cd和Pb的累积效应不很明显,但在研究区的东南部Cd和Pb的地累积指数以及中北部Pb的地累积指数达到了中度污染水平。这些均说明研究区以东铝土资源开发和研究区中部火电厂的生产活动对该区Cd、Pb污染有较大的影响。

滇西勐兴铅锌矿床热液方解石碳氧同位素、稀土元素特征及其指示意义

勐兴铅锌矿床是滇西保山地块内系列低温热液矿床中的典型代表,但地质科研工作相对薄弱。由于方解石是该矿床中分布广泛且与热液活动息息相关的重要脉石矿物,其形成贯穿整个成矿过程,故对其C-O同位素及稀土元素组成特征进行系统研究,以便探讨矿床成矿流体来源及演化。结果显示,该矿床两阶段方解石的δ13 C PDB和δ18 O SMOW值与海相碳酸盐岩较为接近,且从阶段Ⅰ→阶段Ⅱ呈微弱下降趋势,表明成矿流体中的C主要来源于围岩碳酸盐岩的溶解,阶段Ⅱ成矿流体在与围岩反应之前可能已经发生CO 2热液去气作用;阶段Ⅰ方解石的稀土总量、特征参数及配分模式与结晶灰岩较为一致,而阶段Ⅱ方解石与生物碎屑灰岩较为相似,表明阶段Ⅰ方解石中的REE主要来源于结晶灰岩,而后生物碎屑灰岩对阶段Ⅱ方解石中的稀土贡献较大。以上数据及其矿床地质特征均显示该矿床为MVT型铅锌矿床,结合区域构造演化,认为勐兴矿床的形成与中特提斯洋闭合后腾冲地块与保山地块陆陆碰撞挤压密切相关。

喇嘛苏铜矿中酸性岩体岩石学特征

采用费氏台五轴定位法和DCNoble等提出的求斜长石成分和有序度方法、鉴定图表,在喇嘛苏矿区三种中酸性岩体的岩石薄片中选择比较新鲜的、自形程度较好的斜长石,测得斜长石牌号χ(An)=24~56,有序度S=0.4~0.7,说明斜长石以中长石为主,属中温型,即在结晶过程中岩浆冷却的速度较快;斜长石环带有正常环带,也有韵律环带,表明在结晶过程中总体是正常结晶环境,而期间有上下反复运动和岩浆房内压力的反复变化。

北天山西段喇嘛苏铜矿中酸性岩体岩石化学特征及其地质意义

喇嘛苏铜矿区中酸性岩体的皮科克指数、里特曼指数、赖特指数,均指示其中酸性岩体属于钙碱性岩系的范围;分异指数平均值为77.57,说明岩体的分异演化程度较为彻底;固结指数平均值为12.01,显示出岩体的岩浆分异程度较高;长英指数和铁镁指数均反映岩体的分离结晶作用程度中等。在MF—FL分异趋势图上,样品点基本呈连续分布,说明岩体的演化是连续的;在w(Na_2O)—w(K_2O)关系图上多数样品点落入I型花岗岩区域,可以认为本区花岗岩应为I型花岗岩。岩体的TiO_2含量平均为w(TiO_2)=0.28%,远低于中国及世界同类岩石;在戈蒂尼指数与里特曼指数对数值的关系图上,几乎所有的样品点均落在消减带火山岩区,由此可以推断,本区斑岩体应形成于与俯冲作用有关的消减带上。在多阳离子的R1—R2关系图中,多数样品点落在地壳熔融花岗岩-同碰撞的花岗岩区,少数样品点落在其它区域,这说明了岩浆在演化过程中同化混染了围岩。

The geochemical multi-fractal characteristics and mineralization of the Dehelongwa copper-gold deposit

The spatial distribution of ore-forming elements is the result of interaction and influence among multiple factors in the process of mineralization, and is the specific embodiment of non-linearity and coupling of mineralization. The fractal theory has such functions as to characterize non-lineariry and coupling, and can find out the deterministic law from the complicated coupling process. The primary geochemical fractal distribution of metallogenic elements such as Cu and Au possesses the characteristics of multi-fractal distribution in the Dehelongwa copper-gold deposit. Copper follows 2-d fractal distribution, and Au follows 3- or 4-d fractal distribution. The primary geochemical fractal distribution has a certain similarity on the same prospecting line, and this similarity is not obvious among different prospecting lines. The secondary geochemical fractal distribution of Cu and Au is higher in similarity, and simpler than the primary geochemical fractal distribution. These results show that the mineralization of Cu and Au is out of sync and also is inconsistent in this deposit, and the mineralization of Cu mainly experienced two mineralization stages, while the mineralization of Au experienced three to four mineralization stages. Besides the mineralization of Cu and Au shows a certain direction and along the strike of vertical orebodies it is relatively balanced. While along the strike of the ore bodies the mineralization of Cu and Au shows a significant difference. The hypergenic geologic process has a certain effect on the balance of spatial distribution of Cu and Au. From these it can be seen that the mineralization process of this deposit is well characterized by the geochemical fractal distribution of Cu and Au.

Geochemical anomaly structure of South Mining District of Fenghuangshan Copper Mine

To study the geochemical anomaly structure of multi-element associations in the South Mining District of the Fenghuangshan Copper Mine,samples were collected and analyzed for their trace element contents.Multi-element anomaly associations were divided according to the correlations between Cu and each of the other elements,and the distribution characteristics of multi-element anomaly associations were also described.Among them,the anomaly distribution of metallogenic element Cu indicates the environment of mineralization.This study provided the basis for research on the metallogenic prediction and geochemistry of the Fenghuangshan Copper Mine.

右江河谷地区重金属Cd、Pb迁移沉降机制分析

为查明右江河谷地区地形对重金属Cd、Pb分布的影响,分别沿河谷选取11条采样线以及与河谷走向近垂直的小山上选取2条采样线采集浅层土壤样品,并检测土壤中Cd和Pb的含量,结合采样点位置,分析了右江河谷地区浅层土壤中Cd、Pb含量的空间分布特征.结果表明:研究区域土壤中Cd和Pb水平方向分布具有一定的相似性,即东部重金属含量较高,西部次之,中部最低;地形对Cd和Pb分布的影响也具有较好的同步性,均显示出迎风坡含量高,山顶含量低的特点.结合本区的具体情况,测试结果表明:右江河谷地区Cd、Pb主要来源于研究区东部的铝土矿区,风力对Cd、Pb的迁移有较大影响,重力沉降是大气中Cd、Pb沉降的主要方式,大气在水平和垂直方向上的回旋是Cd、Pb沉降的主要原因.