吉林白山刘家堡子狼洞沟金银矿床地球化学特征及成因探讨

通过对刘家堡子-狼洞沟金银矿床地质、成矿元素和同位素地球化学特征的分析和研究,发现矿区内近EW向和NE向断裂构造是主要容矿构造;最佳找矿元素前缘晕组合为As-Sb-Zn,矿上晕元素组合为Au-Ag-Pb-Hg,尾晕元素组合为Ni-Cu-Co;成矿作用中,古老基底中元古宙老岭群变质岩系为成矿提供了丰富的物质来源,而燕山期构造岩浆活动在提供成矿物质的同时还提供了热动力。刘家堡子-狼洞沟金银矿床应划属为与燕山晚期超浅成中酸性岩浆岩有关的中低温热液构造裂隙充填型金银矿床。     

长江中下游宣城水东地区早白垩世酸性火山岩年代学、地球化学及岩石成因

位于长江中下游的宣城水东地区发育一套酸性火山岩,主要由流纹质角砾岩、流纹岩和珍珠岩组成。本文对该套火山岩进行了详细的锆石U-Pb年代学、主量元素、微量元素以及Nd-Hf同位素研究。LA-ICP MS锆石U-Pb定年结果显示3种岩性的火山岩年龄分别为133.2±0.8、133.4±0.8和131.5±0.9 Ma。主量元素组成上,这套酸性火山岩具高硅(72.51%~81.79%)、富钾(K_2O/Na_2O=2.04~14.93,平均6.72)、贫钙镁(Ca O=0.19%~1.57%,Mg O=0.06%~0.29%)的特征,属于弱过铝质(A/CNK=1.02~1.24)的高钾钙碱性-钾玄岩系列岩石。微量元素方面,轻重稀土元素分馏明显[(La/Yb)_N=5.43~9.17],具明显的负铕异常(Eu/Eu~*=0.44~0.60),富集大离子亲石元素(LILE)Rb、Th、K和Pb等,亏损Ba、Sr、Nb、P和Ti等元素,表现出壳源的特征。全岩Sr-Nd和锆石Hf同位素组成变化范围相对较小,(~(87)Sr/~(86)Sr)_i为0.707 3~0.708 8,εNd(t)值为-7.05~-5.56,εHf(t)为-8.6~-1.3。结合区域地质研究成果,认为宣城水东地区酸性火山岩可能是在约135 Ma古太平洋板块俯冲作用之后的伸展-拉伸环境下,由新元古代早期新生地壳重熔而成。     

The source of sulfur in sulfide deposits in the Siberian Platform traps (from isotope data)

The source of sulfur in giant Norilsk-type sulfide deposits is discussed. A review of the state of the problem and a critical analysis of existing hypotheses are made. The distribution of δ³⁴S in sulfides of ore occurrences and small and large deposits and in normal sedimentary, metamorphogenic, and hypogene sulfates is considered. A large number of new δ³⁴S data for sulfides and sulfates in various deposits, volcanic and terrigenous rocks, coals, graphites, and metasomatites are presented. The main attention is focused on the objects of the Norilsk and Kureika ore districts. The δ³⁴S value varies from -14 to + 22.5‰ in sulfides of rocks and ores and from 15.3 to 33‰ in anhydrites. In sulfide-sulfate intergrowths and assemblages, δ³⁴S is within 4.2-14.6‰ in sulfides and within 15.3-21.3‰ in anhydrites. The most isotopically heavy sulfur was found in pyrrhotite veins in basalts (δ³⁴S = 21.6‰), in sulfate veins cutting dolomites (δ³⁴S = 33‰), and in subsidence caldera sulfates in basalts (δ³⁴S = 23.2-25.2‰). Sulfide ores of the Tsentral’naya Shilki intrusion have a heavy sulfur isotope composition (δ³⁴S = + 17.7‰ (n = 15)). Thermobarogeochemical studies of anhydrites have revealed inclusions of different types with homogenization temperatures ranging from 685 °C to 80 °C. Metamorphogenic and hypogene anhydrites are associated with a carbonaceous substance, and hypogene anhydrites have inclusions of chloride-containing salt melts. We assume that sulfur in the trap sulfide deposits was introduced with sulfates of sedimentary rocks (δ³⁴S = 22-24‰). No assimilation of sulfates by basaltic melt took place. The sedimentary anhydrites were “steamed” by hydrocarbons, which led to sulfate reduction and δ³⁴S fractionation. As a result, isotopically light sulfur accumulated in sulfides and hydrogen sulfide, isotopically heavy sulfur was removed by aqueous calcium sulfate solution, and “residual” metamorphogenic anhydrite acquired a lighter sulfur isotope composition as compared with the sedimentary one. The wide variations in δ³⁴S in sulfides and sulfates are due to changes in the physicochemical parameters of the ore-forming system (first of all, temperature and P_ch4) during the sulfate reduction. The regional hydrocarbon resources were sufficient for large-scale ore formation.     

内蒙古兴和县曹四夭超大型斑岩钼铅锌金成矿系统年代学及其地质意义

曹四夭斑岩钼矿床位于内蒙古兴和县,是华北克拉通北缘最大的钼矿床。该矿床中部发育斑岩型钼矿体,外围和上部产出热液脉型铅锌金矿体。文章选取1件与斑岩钼矿化共生的绢云母样品进行了40Ar-39Ar定年,获得40Ar-39Ar坪年龄为(144.4±1.2)Ma,相应的39Ar/36Ar-40Ar/39Ar等时线年龄为(146.4±2.2)Ma(MSWD=0.31),将等时线年龄认作绢云母的Ar封闭年龄,表明曹四夭斑岩钼矿化发生在约146 Ma前。选取14件脉型铅锌矿石中的闪锌矿、黄铁矿和磁黄铁矿样品开展了Rb-Sr定年,获得4件闪锌矿的Rb-Sr等时线年龄为(145.1±3.0)Ma(MSWD=0.63);5件黄铁矿的Rb-Sr等时线年龄为(145.2±1.3)Ma(MSWD=0.53);4件闪锌矿、5件黄铁矿和1件磁黄铁矿的Rb-Sr等时线年龄为(145.3±1.0)Ma(MSWD=0.43)。硫化物Rb-Sr定年结果表明曹四夭矿床脉型铅锌矿化形成于约145 Ma前。本次绢云母40Ar-39Ar和硫化物Rb-Sr定年结果表明,曹四夭矿床斑岩型钼矿化和脉型铅锌金矿化为同期产物,两者均形成于晚侏罗世末期,属于同一个斑岩成矿系统。曹四夭矿床硫化物的w(Rb)和w(Sr)分别为0.1867×10~(-6)~1.305×10~(-6)和0.3175×10~(-6)~6.935×10~(-6),Sr同位素初始比值(87Sr/86Sr)i介于0.709 919~0.711 951之间,平均值0.710 952,结合前人获得的辉钼矿Re含量,认为曹四夭矿床的成矿物质主要来源于地壳。     

微波消解-电感耦合等离子体质谱法测定海泡石中的稀土元素

海泡石是一种纤维状含水的富镁硅酸盐黏土矿,其中的稀土元素含量在1×10~(-7)～1×10~(-5)之间,目前还没有建立海泡石中稀土元素的国家标准分析方法。测定岩石中的稀土元素主要是采用电感耦合等离子体质谱法(ICP-MS),样品前处理一般采用封闭溶矿和碱熔,但这两种处理方法耗时较长,效率不高。本文通过比较硝酸-氢氟酸-过氧化氢、硝酸-氢氟酸、硝酸-过氧化氢三种样品前处理方法,确定使用硝酸-氢氟酸溶矿,然后进行微波消解同时赶去氢氟酸,避免氢氟酸与稀土元素生成难溶的氟化物,再采用ICP-MS法测定15种稀土元素的含量。由于海泡石中的镁含量较高,为降低基体效应,以~(103)Rh和~(185)Re作内标补偿基体效应和校正灵敏度漂移,各元素测定值的准确性显著提高,回收率为91. 2%～110. 9%,检出限为0. 002～0. 011μg/L,精密度≤2. 79%。本方法与封闭酸溶ICP-MS法的分析结果吻合较好,且用酸量少(7 mL),溶矿效率高(1 h),检出限更低。     

塔里木盆地玉尓吐斯组高频层序沉积充填演化特征及控烃作用

结合9个野外剖面和17口井,对塔里木盆地玉尔吐斯组沉积演化及其对烃源岩的制约作用进行了系统研究和分析。在精细对比后发现,塔里木盆地下寒武统玉尔吐斯组可分为2个三级层序(SQ1、SQ2)、5个四级层序(sq1—sq5),其中三级层序SQ1可分为3个四级层序,SQ2可分为2个四级层序。SQ1发生在寒武纪初期,海进速度较慢,影响范围相对局限,而SQ2的海进则相对迅速,影响范围较大。四级层序sq1发生在第一次海侵初期,水体浅,主要沉积紫红色白云岩、灰黑色砂屑白云岩,起填平补齐的作用;sq2、sq4发生在海侵—海退的转换时期,是两套深水的沉积,岩性以黑色泥岩、硅质泥岩和硅质岩为主,局部发育泥岩与条带状白云岩互层;sq3、sq5是海退过程中的浅水沉积,主要发育灰色白云岩和藻白云岩,局部有泥质夹层。利用Mn、Fe、Ti、Rb、K、Sr、Ba、Cu、U、V、Mo等元素及其比值进行沉积环境分析表明,sq2时期,水体深度大、盐度低、气候温暖湿润,有利于生物发育,并且其硫化缺氧的环境极其有利于有机质的保存;sq4时期,水体深度较大,盐度相对较小,气候相对温暖湿润,较为适合生物生存,并且其硫化缺氧夹次氧化的环境,较为适合有机质保存。高频海平面变化与沉积环境演化影响着玉尔吐斯组的烃源岩分布与品质,sq2时沉积的烃源岩品质优于sq4,但是其分布范围小于sq4。     

Dissolution characteristics of deep?buried dolostone in the Member 5 of Ordovician Majiagou Formation in southern Ordos Basin

The different types of deep-buried dissolution process in the Member 5 of Ordovician Majiagou Formation in the southern Ordos Basin and its influence on the reservoir properties are studied in this paper. It shows that three types of mechanisms include organic acid fluid, hydrothermal fluid and TSR are identified through studies of core observation, thin section analysis, inclusion temperature, trace elements and rare earth elements. It is found that the dissolution of organic acid fluid causes the stratified dissolution pores, film-like asphaltene and ring-like asphaltene, while hydrothermal fluid causes the non-selective dissolution pores without petrofabric, veins of pyrites, massive pyrites and the association of hypothermal minerals. Four occurrence models of dissolution include, (1) the deep-buried dissolution of low-temperature hydrothermal fluid occurs in Zhiluo Period of Middle Jurassic; (2) the deep-buried dissolution of organic acid fluid started from the late Middle Jurassic followed by the first hydrocarbon injection; (3) the deep-buried dissolution of middle-high temperature hydrothermal fluid occurred in the Dongsheng Period of Early Cretaceous; (4) TSR occurred at the end of Early Cretaceous with the second larger hydrocarbon injection. Both organic acid fluid and hydrothermal fluid can improve the porosity and permeability of reservoir, but the hydrothermal fluid is more effective than that of organic acid fluid.     

五酸溶样-电感耦合等离子体质谱法同时测定地质样品中的稀土等28种金属元素

电感耦合等离子体质谱法(ICP-MS)测定大批量地质样品中的稀土和钴铪铟锰铌钽铊铬镉镓锗钒锡等金属元素,主要采用三酸或四酸溶解样品.由于地质样品组分复杂,稀土等金属元素含量低,各元素性质差异大,三酸或四酸溶样经常出现易挥发元素如钒铬镉镓锡的测定结果不稳定、镧铈镨钕等稀土元素溶解不完全的问题.本文在盐酸-硝酸-氢氟酸-高...     

闽西南地区块状硫化物矿床的喷流-沉积成矿作用

通过对闽西南地区石炭纪—早二叠世主要块状硫化物矿床的区域成矿背景、贮矿层位特征以及矿石矿物成分、结构构造,硫同位素地球化学特征、成矿温度等分析研究,指出该地区石炭纪—早二叠世块状硫化物矿床的形成多与海底火山活动有关,贮矿层中伴有典型的喷流沉积岩—硅质岩,并提出闽西南地区块状硫化物矿床存在海底喷流-沉积成矿作用的新认识。     

酸溶法测定硫铁矿中的全硫

在野外地质队实验室仪器少的条件下,用酸溶的方法分析硫铁矿中全硫,简单、快速、易操作,取得良好的结果。