EXPERIMENTAL GEOCHEMISTRY STUDY ON GOLD IN WATER-ROCK REACTION UNDER THERMAL FLUID SYSTEM AT MESO-LOW TEMPERATURE

Based on the knowing geochemical characteristics of wall rock in the Mobin gold deposit and composition of fluid inclusion in ore,water-rock experiments were carried out,important achievements are acquired as following: Gold is mainly derived from the ore-bearing wall rock,i,e.,a series of epimetamorphic clastic gritstone,sandy slate,and tuffaceous slate in the Wuqiang Banxi Formation,Wuqiangxi Group.In thermal system with middle-low temperature chlorine gold may be derived form stable complex ions,so it is quite important in gold metallogenic process.Sulphur and chlorine perform as the major negative ions throughout the gold activation and migration movement.The concentration of sulphur and chlorine ions,pH value and temperature are of deciding significance for gold activation,migration and precipitation.     

No-association of proportions

This note has three purposes: to briefly review the role of neutrality as a criterion of no-association of proportions; to compare neutrality with a criterion proposed by Snow in this journal; to describe a simple test of neutrality in the median.     

Dissolved chromium in the St. Lawrence estuary

A study of dissolved chromium in the St. Lawrence estuary and Gulf of St. Lawrence has been carried out. A chromium concentration of 0·7 μg l^?1 was found in the St. Lawrence River. In the turbidity maximum of the upper estuary, chromium is removed from solution onto fine-grained resuspended sediments and internally produced organic-rich floccules. A simple flux calculation shows that these processes remove ～50% of the total dissolved chromium input of the river. At salinities greater than 5‰ dissolved chromium mixes conservatively.     

吉林东部延吉地区中生代火山岩地球化学特征

吉林东部延吉地区大面积出露的中生代火山岩,根据岩性特征可分为三个火山喷发旋回。各旋回火山岩均属ＳｉＯ２过饱和的中基性—中酸性岩类。从第一旋回至第三旋回岩石碱度变化较大,岩浆分异明显,特别是第三旋回分异作用明显高于第一、二旋回。火山岩中金、铜微量元素的平均含量普遍高于同类岩石的克拉克值几倍至几十倍,而且随着岩浆分异程度的升高,其平均含量有明显升高的趋势,为本区金、铜矿床的形成提供了物质来源。     

内蒙古西乌旗沙尔哈达晚侏罗世A型花岗岩：地球化学特征、岩石成因与动力学背景

内蒙古西乌旗沙尔哈达花岗岩侵入于贺根山缝合带蛇绿岩中。LA-ICP-MS锆石测年指示,沙尔哈达花岗岩岩株于晚侏罗世(154.6±1.2 Ma)侵位,矿物组合以石英、碱性长石和斜长石为主,富SiO2(74.86%~75.97%)、K2O(4.4%~4.95%),贫MgO(0.044%~0.22%)、CaO(0.38%~0.77%)、TiO2(0.046%~0.18%)和P2O5(0.007%~0.042%),A/CNK=1.03~1.09, 小于1.1,强烈亏损Ba、Sr、Eu、P、Ti,具有典型的右倾“海鸥型”稀土元素分配模式,表现出典型的铝质A型花岗岩的矿物组合及地球化学特征。沙尔哈达A型花岗岩具有低的(87Sr/86Sr)i值(0.7014~0.70374)、低正εNd(t)值(+3.96~+4.31)、高的εHf(t)值(+10.54~+14.72)。同位素地球化学特征指示,沙尔哈达花岗岩可能源于新生的中基性地壳物质部分熔融及其后的结晶分异作用。沙尔哈达A型花岗岩为晚侏罗世蒙古-鄂霍茨克洋闭合后造山伸展作用的产物,和蒙古-华北北部地块散布的其他A型花岗岩共同指示中晚侏罗世广泛的中下地壳伸展。     

新疆西准噶尔沙勒克腾地区花岗岩锆石U-Pb年龄、地球化学特征及其对后碰撞构造环境的约束

以西准噶尔白杨河上游沙勒克腾山及周缘花岗岩为研究对象,在地质调查的基础上,进行岩石学、锆石U-Pb年龄、岩石地球化学特征研究,探讨其形成时代及构造背景。西准噶尔白杨河上游沙勒克腾山及周缘花岗岩可划分为沙勒克腾、查干恩干、阿拉乔古、坦子不拉克4个序列,各序列岩石组合分别为花岗闪长斑岩、二长花岗斑岩,碱长花岗岩、正长花岗岩,闪长玢岩、闪长岩、石英闪长玢岩,二长花岗斑岩、花岗斑岩。沙勒克腾序列锆石U-Pb年龄为302.1±1.4 Ma(n=26,MSWD=1.5),形成时代为晚石炭世;具有低硅(SiO2=68.07%~70.49%)、贫碱(K2O+Na2O=7.23%~8.18%)、富铝(Al2O3=14.12%~15.69%)、富钛(TiO2含量0.43%~0.48%)、富钙(CaO含量1.71%~3.31%)特征;相对亏损Nb、Ta、Sr、P、Ti,富集Zr、Hf。查干恩干序列锆石U-Pb年龄为296.7±2.1 Ma(n=26,MSWD=0.41),形成时代为早二叠世早期;具有相对高硅(SiO2=74.21%~74.37%),富碱(K2O+Na2O=8.84%~9.19%)、富铝(Al2O3=12.59%~12.85%),低钛(TiO2=0.19%~0.22%)、低钙(CaO=0.64%~1.24%)特征;稀土元素含量低,亏损Sm、Tb、Y、Yb、Lu、Sr,富集Zr、Hf。沙勒克腾序列、查干恩干序列、阿拉乔古序列、坦子不拉克序列分别属于准铝质—弱过铝质高钾钙碱性I型花岗岩、准铝质碱性高分异I型花岗岩、弱过铝质碱性I型花岗岩、S型花岗岩。研究表明,白杨河上游库勒克腾山及周缘花岗岩形成于后碰撞环境挤压应力体制向伸展应力体制转换期,查干恩干序列的侵位标志着区域应力体制进入伸展阶段,进而限定研究区进入伸展应力体制的时限应不晚于296.7±2.1 Ma,为西准噶尔地区晚石炭世—早二叠世后碰撞构造研究提供了新的依据。     

Geochemical and isotopic composition of organic matter in the Kupferschiefer of the Polish Zechstein basin: relation to maturity and base metal mineralization

max vs the present depth of the Kupferschiefer, soluble organic matter (SOM) yields, and relative proportions of saturated and aromatic hydrocarbons of the SOM provide evidence for an oxidative alteration of organic matter in highly mineralized Kupferschiefer samples near the Rote F?ule zones. This is confirmed by differences in the composition of the saturated and aromatic hydrocarbon fractions of the soluble organic matter: Saturated hydrocarbons from Rote F?ule samples are dominated by short-chain n-alkanes and higher abundances of pristane and phytane relative to heptadecane (n-C17) and octadecane (n-C18), respectively, compared with samples more distant to the Rote F?ule zone. Compositional changes of the aromatic hydrocarbon fractions with decreasing distance to that zone are characterized by the occurrence of polycyclic aromatic hydrocarbons and elevated ratios of phenanthrene to methylphenanthrenes that are attributed to demethylation reactions and resulted in a decrease of the methylphenanthrene index (MPI 1). Kupferschiefer samples from the barren zone of the Polish Basin do not show these alteration patterns. The observed variations in organic matter composition with burial depth are consistent with changes due to increasing thermal maturation. Maturity assessment is achieved from MPI 1 and the methyldibenzothiophene ratio (MDR). From the relationship between the maturity of organic matter in terms of vitrinite reflectance values and depth of the Kupferschiefer strata, a continuous increase in reflectance of vitrinite is obtained within the Polish Basin. The alteration pattern of organic matter related to base metal mineralization of the Kupferschiefer corresponds to changes in the isotopic composition of organic carbon and calcite. Kerogen within, or close to, Rote F?ule zone is enriched in ¹³C caused by the preferential release of isotopically light organic compounds through progressive degradation of organic matter. The opposite tendency towards lower δ ¹³C and δ ¹⁸O values of calcite provides evidence for isotopic exchange between carbonate and the oxidizing, ore-bearing solutions and for organic matter remineralization. In contrast, organic matter and calcite from the Kupferschiefer do not show regular trends in δ ¹³C with increasing thermal maturation. Received: 25 June 1999 / Accepted: 1 December 1999     

北京十三陵元古宙大红峪组含事件信息的沉积岩研究

北京十三陵元古宙大红峪组在不足４ｋｍ的距离内岩相急剧变化,实为国内外罕见。从东至西,泰陵剖面由灰色角砾硅化岩＋黑色粉砂凝灰页岩＋黄色含长石石英砂岩组成,山顶部面由不纯砂岩＋泥质白云岩组成,德胜口剖面由泥质白云岩＋石英砂岩＋层凝灰岩组成。本文仅对泰陵剖面大红峪组的三种岩石进行系统研究。宏观、微观特征、地球化学和同位素地球化学分析数据表明：泰陵剖面大红峪组的灰色角砾硅化岩和黑色粉砂凝灰页岩是受火山－地     

大兴安岭中南段金属矿床流体包裹体研究

作者通过在不同温度下对包裹体特征、相变行为的系统观察与测定，以及对包裹体气、液相成分的分析、获取了研究区内主要矿床成矿过程中成矿液体的温度、盐度、密度、流体成分、流体的沸腾现象、成矿压力以及ＰＨ，Ｅｈ，Ｆｏ２，还原参数等成矿的物理化学参数，从而为划分矿化蚀变阶段，矿床类型、成矿系列和深化对矿床成矿作用与成矿机制的认识提供了科学依据。尽管矿床属于不同的成矿系列，只要矿床类型相同，矿床的流体包裹体地球     

多宝山超大型铜矿床的成矿构造环境

多宝山超大型铜矿床是我国典型的斑岩型矿床，主要产出于多宝山组岛弧建造和花岗闪长岩、花岗闪长斑岩中，成矿年龄为292～283Ma。根据地球物理异常及大量的基性和超基性岩体，以及通过对比两侧的岩石圈结构、古生物、结晶基底、成矿特征和地球化学特征，认为黑河一嫩江是一条重要的构造边界带，它是兴安和松嫩地块在早石炭世拼合、碰撞、造山隆起形成的。多宝山超大型铜矿床就是形成于两板块碰撞后隆起抬升构造环境的斑岩型铜矿床。