南秦岭大型钡成矿带中毒重石矿床成因新认识——来自单个流体包裹体证据

钡以BaSO_4形式存在的重晶石矿床在世界上广泛分布,但以BaCO_3形式存在的毒重石矿床极为罕见。在南秦岭早古生代硅岩建造中,发育大量层状毒重石和重晶石矿床,两类矿床在空间上表现出既共生又分离的分布规律,构成世界上极为独特的大型钡成矿带。本文对毒重石、钡解石、重晶石及石英等矿物流体包裹体进行了系统研究,结果显示,各矿物中流体包裹体的均一温度都变化于90～310℃,主要集中范围为120～220℃。尽管如此,毒重石、钡解石的形成温度峰值比重晶石高出40℃,而石英的形成温度分布较均一,没有出现明显的峰值。矿物流体包裹体的盐度虽变化于1%～15%NaCl_(eqv),但毒重石、钡解石和石英样品中的盐度值普遍大于5%NaCl_(eqv),而重晶石中的盐度值小于5%NaCl_(eqv)的样品数量占有相当大的比例。由于重晶石的流体包裹体主要以NaCl-H_2O型包裹体为主,而毒重石中富含大量N_2-CO_2-H_2S-CH_4等复杂组分水溶液型包裹体,显示出毒重石与重晶石在成矿环境上有较大差异。由此笔者明确提出,水溶液热化学硫酸盐还原作用是形成毒重石矿床主要机制的新认识。     

陕西神河钡矿床矿物流体包裹体特征与成矿物理化学条件

陕西神河钡矿床位于南秦岭钡成矿带的北矿带,重晶石和毒重石为主要的矿石组成.显微测温分析表明,重晶石、毒重石和钡解石内流体包裹体的均一温度范围分别为108～205℃(峰值130～170℃)、118～274℃(峰值150～210℃)和146～227℃;盐度w(NaCleq)分别为0.53％ ～9.86％、0.18％ ～8....     

南秦岭钡成矿带重晶石与毒重石成矿特征

在我国扬子地块北缘南秦岭一带的早古生代硅质岩建造中,存在一大批重晶石矿床和毒重石矿床,构成世界上极为罕见的大型钡成矿带。根据流体包裹体显微测温分析,重晶石流体包裹体均一温度峰值低于毒重石流体包裹体峰值。这些矿床中重晶石的3δ4S值比同期海水3δ4S值高(除去文峪矿区重晶石一个3δ4S值与同期海水3δ4S值接近),表明当时细菌对硫酸盐的还原作用引起了重S的富集。各钡矿床中的毒重石有各自的1δ3C和1δ8O值范围,毒重石中的C来自有机质事件反应。根据热力学计算表明,小于162.42℃的温度有利于形成重晶石矿石;在温度高于162.42℃时,海水中积累充足的CO32-(来自有机事件)有利于形成毒重石矿石。在重晶石矿床形成的晚期,如出现贫Ba2+热液,且海水中积累足够的CO32-和温度高于162.42℃,CO32-可以交代重晶石中的SO42-,形成交代成因的毒重石。     

西藏甲玛铜多金属矿床成因研究——来自流体包裹体的证据

甲玛铜多金属矿床位于西藏冈底斯斑岩铜矿带东段,是近年来勘探发现的超大型斑岩-矽卡岩型铜多金属矿床。通过冷热台显微观察与测温、扫描电镜、激光拉曼探针测试,对甲玛矿床各成矿阶段典型矿物的流体包裹体研究表明,成矿流体富含挥发分,临界相均一的流体来自岩浆超临界流体出溶,主成矿阶段具有沸腾包裹体组合特征,有机质包裹体荧光效应显著。显微测温结果显示,岩浆-热液阶段斑岩中石英斑晶的流体包裹体均一温度范围为250～540℃,含石盐子晶高盐度包裹体盐度范围为35～61(wt%)NaCl.eq,中等盐度的临界均一的气液包裹体盐度范围为3～29(wt%)NaCl.eq,岩浆期后热液阶段斑岩、角岩中石英脉的流体包裹体均一温度范围为210～410℃,盐度范围为33～41(wt%)NaCl.eq,与其不混溶共生的中低盐度气液两相流体包裹体盐度范围为5～25(wt%)NaCl.eq。矽卡岩阶段矿物均一温度范围为130～360℃,盐度范围为3～41(wt%)NaCl.eq,从岩浆热液过渡阶段到石英-硫化物阶段均一温度与盐度呈阶梯式降低趋势。斑岩体石英的流体包裹体中含有较多黄铜矿子矿物,岩浆结晶分异过程中已经具成矿元素的富集。激光拉曼探针测试结果显示,成矿早期至主成矿期矿物流体包裹体气相成分主要为CO2、CH4和N2,各阶段矿物流体包裹体气相成分具有继承性。成矿流体为高温度高盐度,富含CO2、CH4的流体。成矿流体主要源于岩浆,后期混有大气降水。当岩浆热液上升时因压力的突然释放造成高温含矿热流体发生减压沸腾,CO2和CH4等气体大量逃逸,导致成矿物质快速沉淀。矿床在成因上与岩浆-热液成矿作用密切相关。     

内蒙古额尔古纳地区比利亚谷铅锌(银)矿床成矿流体特征与矿床成因北大核心CSCD

比利亚谷矿床是内蒙古额尔古纳成矿带内新发现的一个铅锌（银）矿床,具有大型矿床的成矿潜力。主矿体呈脉状产于上侏罗统塔木兰沟组和满克头鄂博组火山岩地层中,受NW,NWW向张性断裂构造控制;主要金属矿物有方铅矿、闪锌矿、黄铁矿、黄铜矿、辉银矿等。为确定该矿床的成矿流体特征及成因类型,对矿石中的石英、重晶石和闪锌矿开展了流体包裹体的岩相学观察、显微测温和激光拉曼光谱分析。结果表明,上述矿物中主要发育富液相、CO2三相和少量含子矿物三相包裹体;富液相包裹体的均一温度与盐度分别为102℃～378℃和0．2％～10．5％NaCleqv,CO2三相包裹体的均一温度和盐度分别为124℃～256℃和1．8～11．2％NaCleqv,舍子矿物三相包裹体的均一温度与盐度分别为220℃和42．4％NaCleqv。单个流体包裹体气相成分的激光拉曼光谱分析显示,除石英中的部分富液相包裹体的气体成分含CO2外,不同矿物中的富液相包裹体的气体成分均为H2O。此外,该矿床成矿流体的盐度范围波动较大,重晶石中包裹体的均一温度分布范围较广,因此成矿流体属不均匀流体,流体混合作用是该矿床的重要成矿机制。综合认为,比利亚谷铅锌（银）矿床应属赋存于中生代火山岩中的与浅成一超浅成岩浆作用有关的中低温热液脉型矿床。     

内蒙古额尔古纳地区比利亚谷铅锌(银)矿床成矿流体特征与矿床成因

比利亚谷矿床是内蒙古额尔古纳成矿带内新发现的一个铅锌(银)矿床,具有大型矿床的成矿潜力。主矿体呈脉状产于上侏罗统塔木兰沟组和满克头鄂博组火山岩地层中,受NW,NWW向张性断裂构造控制;主要金属矿物有方铅矿、闪锌矿、黄铁矿、黄铜矿、辉银矿等。为确定该矿床的成矿流体特征及成因类型,对矿石中的石英、重晶石和闪锌矿开展了流体包裹体的岩相学观察、显微测温和激光拉曼光谱分析。结果表明,上述矿物中主要发育富液相、CO2三相和少量含子矿物三相包裹体;富液相包裹体的均一温度与盐度分别为102℃~378℃和0.2%~10.5%NaCl eqv,CO2三相包裹体的均一温度和盐度分别为124℃~256℃和1.8~11.2%NaCl eqv,含子矿物三相包裹体的均一温度与盐度分别为220℃和42.4%NaCl eqv。单个流体包裹体气相成分的激光拉曼光谱分析显示,除石英中的部分富液相包裹体的气体成分含CO2外,不同矿物中的富液相包裹体的气体成分均为H2O。此外,该矿床成矿流体的盐度范围波动较大,重晶石中包裹体的均一温度分布范围较广,因此成矿流体属不均匀流体,流体混合作用是该矿床的重要成矿机制。综合认为,比利亚谷铅锌(银)矿床应属赋存于中生代火山岩中的与浅成-超浅成岩浆作用有关的中低温热液脉型矿床。     

内蒙古白乃庙石英脉群流体包裹体特征及其金的勘查意义

研究区位于内蒙古白乃庙—谷那乌素铜金成矿带,地质填图发现:白乃庙铜金矿床西侧徐尼乌苏组中发育一套石英脉群,产状与白乃庙矿区金矿化石英脉相似。其矿物组合可分为黄铁矿-石英早阶段(M1)和石英-方解石晚阶段(M2)。M1阶段捕获的流体包裹体中,含子晶三相包裹体均一温度为256~320℃,盐度为31.4%~39.8%NaCl eqv;两相水溶液包裹体的均一温度为210~260℃时,盐度为17.1%~22.8%NaCl eqv,气相富集CH4,CO2次之,含H2S、H2O及少量C6H6、N2,温度为170~210℃时,气相富集H2O或CO2,CH4次之,含N2,盐度与前者相似,但存在低盐度流体端员;纯气体包裹体成分为纯CH4或者CO2和CH4。M2阶段捕获两相水溶液包裹体,均一温度为90~160℃,盐度为15.82%~21.1%NaCl eqv,并与低盐度流体混合。石英脉群的流体可以看作中低温中低盐度含H2S、N2、C6H6的CH4-CO2-H2O-NaCl体系。对比金矿床成矿流体、白乃庙铜金矿床流体特征并结合化学分析,表明石英脉群具有金矿化的潜力。     

山西中条山铜矿峪铜矿流体演化特征

铜矿峪铜矿大地构造位置位于华北克拉通中部造山带南部,主容矿围岩为花岗闪长斑岩、二长花岗岩及变质基性火山岩。对不同阶段石英流体包裹体进行了包裹体岩相学、显微测温学和激光拉曼显微探针研究。结果表明,成矿流体包裹体可分为气液两相包裹体、含多子晶包裹体、含石盐子晶包裹体、含CO2 包裹体及纯CO2 包裹体。其中早阶段以富含多子晶包裹体( 均一温度为436. 2 ℃ ～ ＞ 550 ℃,盐度( w ( NaCl) ) 为49. 34% ～ ＞ 62%) 和含石盐子晶包裹体( 均一温度为345. 6 ℃ ～ ＞ 550 ℃,盐度( w ( NaCl) ) 为29. 72% ～ ＞ 62%) 为主。主成矿阶段主要由含石盐子晶包裹体( 均一温度为169. 1 ℃ ～ 324. 9 ℃,盐度( w ( NaCl) ) 为30. 47% ～ 39. 75%) 、气液两相包裹体( 均一温度介于159. 9 ℃ ～ 242. 9 ℃,盐度( w ( NaCl) ) 为1. 56% ～ 22. 31%) 组成并发现少量含CO2 包裹体 ( 均一温度为259. 7 ℃ ～ 320. 5 ℃,盐度( w ( NaCl) ) 为8. 93% ～ 13. 16%) 和纯CO2 包裹体( CO2 均一温度为24. 3 ℃ ～ 27. 22 ℃) 。晚成矿阶段仅发育气液两相包裹体( 均一温度为126. 9 ℃ ～ 212. 3 ℃,盐度( w ( NaCl) ) 为1. 56% ～ 7. 44 %) 。激光拉曼光谱分析包裹体气相成分主要为H2O、CO2、 HF 组成,晚期为CO2、N2。包裹体中普遍存在CO2。早阶段流体应为高温高盐高氧逸度NaCl － H2O － CO2 体系。主成矿阶段含气液两相包裹体与富CO2 相包裹体共存,表明流体发生了不混溶或沸腾现象。成矿晚阶段低温低盐度气液两相包裹体可能来源于大气降水。分析认为,铜矿峪铜矿成因类型属斑岩型。     

四川阿坝州党坝伟晶岩型锂辉石矿床流体包裹体特征及地质意义

四川省阿坝州党坝伟晶岩型锂辉石矿床是可尔因稀有金属矿集区内的典型矿床。通过对党坝锂辉石矿物流体包裹体研究结果表明:1)锂辉石矿物中富集气液两相水溶液包裹体、含CO2三相包裹体,见少量含子矿物三相包裹体;流体包裹体均一温度为260℃-314℃,盐度为w(NaCl,eqv)=2.96%~9.08%,指示党坝矿床成矿流体具中温、低盐度特征。2)激光拉曼光谱分析气相成分主要为H2O,CO2次之,见少量的CH4、N2;液相成分以H2O为主,含少量CO2、CH4;含子矿物包裹体的子晶矿物为方解石。3)成矿流体应属H2O-NaCl±CO2±CaCl2±CH4±N2体系,流体密度为0.72~0.88g/cm3,认为在成矿流体主要来源于岩浆热液。4)气液两相水溶液包裹体、含CO2三相包裹体以及含子矿物三相包裹体共存于同一视域中,且均一温度相近,表明流体发生沸腾或不混溶作用导致相分离并发生锂辉石聚集沉淀是党坝锂辉石矿床形成的主要原因。     

浙江建德铜矿流体包裹体研究

浙江建德铜矿(原名岭后铜矿)是20世纪60年代初期探明的中型铜矿,位于扬子板块和华夏板块结合带(即钦杭结合带)北东段。文中系统研究了建德铜矿主成矿期块状矿石石英中的流体包裹体。岩相学研究表明主要发育三类包裹体:包括富液相包裹体(I型),富气相包裹体(II型),以及含子晶包裹体(III型);显微测温结果显示:I类富液相包裹体加热后均一到液相,均一温度分布范围主要集中在280~340℃,流体包裹体盐度0.63~8.00 wt.%Na Cl eqv,II类富气相包裹体加热均一到气相,均一温度296~334℃,盐度1.22~2.00 wt.%Na Cl eqv的低盐度范围,III类含子晶包裹体,均一温度范围与II类包裹体基本相同,介于290~326℃,盐度则较高,介于31.87~38.16 wt.%Na Cl eqv。激光拉曼探针分析揭示,流体挥发分主要为水蒸气,同时部分包裹体气相组分中含有CO2、CH4、N2。II类与III类流体包裹体在视域内共存,且两者均一温度相似,盐度相差很大,表明强烈的流体沸腾作用发生。流体强烈沸腾作用是造成建德铜矿成矿物质沉淀富集的原因。成矿流体研究结合地质特征表明,建德铜矿是燕山期的矽卡岩型矿床而不是海西期的喷流沉积矿床。     

岩溶地区现代土壤与洞穴石笋中单甲基支链烷烃与烷基环己烷对比研究

利用GC-MS（气相色谱—质谱仪）,对采自湖北清江流域和尚洞洞顶的土壤样品与洞内石笋样品进行分析,发现土壤中存在的七个系列单甲基支链烷烃在所有的石笋样品中均可以找到,呈现相似的分布模式,石笋中七个系列支链烷烃有可能来自洞穴滴水携带的土壤中的支链烷烃,但是也不能排除石笋原地生长的微生物的贡献。烷基环己烷的分布在土壤与石笋中呈现了相似的分布模式,但是主峰碳数有所变化,高碳数部分与低碳数部分的相对含量也发生了变化。主要原因可能是微生物选择性降解的结果,也有可能是土壤与石笋中微生物种类分布差异所造成的。本次研究初步显示了相对封闭稳定的洞穴沉积物与上覆土壤层中生物标志化合物的异同。      

Hydrogen and carbon in solid solution in oxides and silicates

The dissolution of H₂O and CO₂ in structurally dense, nominally anhydrous and non-carbonate oxide matrices such as MgO and CaO is reviewed. H₂O and CO₂ are treated as gaseous oxide components which enter into solid solution with the refractory oxide hosts. They form anion complexes associated with cation vacancy sites. Evidence is presented that OH^? pairs which derive from the dissolution of H₂O are subject to a charge transfer (CT) conversion into peroxy moieties and molecular hydrogen, O ₂ ^2? ... H₂. Because the O ₂ ^2? moiety is small (O^?-O^? distance ≈ 1.5 Å) high pressure probably favors the CT conversion. Mass spectroscopic studies show that molecular H₂ may be lost from the solid which retains excess oxygen in the form of O ₂ ^2? , leading to the release of atomic O. The dissociation of O ₂ ^2? moieties into a vacancy-bound O^? state and an unbound O^? state can be followed by measuring the internal redox reactions involving transition metal impurities, the transient paramagnetism of the O^? and their effect on the d.c. conductivity. Evidence is presented that CO₂ molecules dissolve dissociatively in the structurally dense oxide matrix, as if they were first to dissociate into CO+O and then to form separate solute moieties CO ₂ ^2? and O ₂ ^2? , both associated with cation vacancy sites. In the CO ₂ ^2? moiety (C-O^? distance 1.2–1.3 Å, OCO angle ≈ 130°) the C atom probably sits off center. The transition of the C atom into interstitial sites is accompanied by dissociation of the CO ₂ ^2? moiety into CO^? and O^?. This transition can be followed by infrared spectroscopy, using OH^? as local probes. Further support derives from magnetic susceptibility, thermal expansion, low frequency dielectric loss and low temperature deformation measurements. The recently observed emission of O and Mg atoms besides a variety of molecules such as CO, CO₂, CH₄, HCN and other hydrocarbons during impact fracture of MgO single crystals is presented and discussed in the light of the other experimental data.     

Geogenic and anthropogenic zinc in epiphytic and terricolous lichens in Finland

At 31 sites in Finland the Zn content was determined of the epiphytic lichen Hypogymnia physodes (L.) Nyl. growing on pine and birch, the terricolous lichen Cladina spp. in pine bark, and the inner part of birch bark. The anomalous contents of Zn in H. physodes on pine and Cladina spp. in soil appeared to be strongly related to sulphide ore deposits. Anthropogenic Zn correlated closely with S and Fe in H. physodes on pine and with Fe in Cladina spp. The binding of geogenic Zn was related to iron hydroxides, and was attributed to the different uptake mechanism of S in these lichens. Elevated values of Zn in H. physodes on birch were due to both geogenic and anthropogenic sources. Zinc in pine bark increased with the Zn content in H. physodes and reached a limiting value.     

Comparative urbanization in Ghana and Kenya in time and space

There are few inter-African country urban analyses because of the continent’s enormous size and socioeconomic diversity, language barriers, and wide variations in national and regional urban research capacity. Nevertheless, comparative urban studies are critical in understanding contemporary African urbanization. In this comparative spatial and temporal analysis of Ghana and Kenya’s urbanization, we find that both countries are urbanizing rapidly and are faced with many common urban problems. Moreover, Ghana is more urbanized than Kenya and has a larger indigenous urban imprint and a more widely dispersed urban pattern. Besides their physiographic and population conditions, we trace these countries’ convergent and divergent urban trends to their shared but unique experiences of colonialism, nationalism and globalization.     

Temporal and spatial variations in water discharge and sediment load in the Alaknanda and Bhagirathi Rivers in Himalaya, India

The Alaknanda and Bhagirathi Rivers originate in the mountainous regions of the Himalayas (Garhwal) and result in high sediment yields causing flood hazards downstream of the Ganga River and high sediment flux to the Bay of Bengal. The rivers are perennial, since runoff in these rivers is controlled by both precipitation and glacial melt. In the present study, three locations in the upper reaches of the Ganga River were monitored for 1 yr (daily observations of, more than >1000 samples) for suspended sediment concentrations. In addition, more than one hundred samples were collected from various locations of the Alaknanda and Bhagirathi Rivers at different periods to observe spatial and temporal variations in river suspensions. Further, multi-annual data (up to 40 yrs) of water flow and sediment concentrations were used for inferring the variations in water flow and sediment loads on longer time scales. In most previous studies of Himalayan Rivers, there has been a general lack of long term water flow and sediment load data. In the present study, we carried out high frequency sampling, considered long term discharge data and based on these information, discussed the temporal and spatial variations in water discharge and sediment loads in the rivers in the Himalayan region. The results show that, >75% of annual sediment loads are transported during the monsoon season (June through September). The annual physical weathering rates in the Alaknanda and Bhagirathi River basins at Devprayag are estimated to be 863 tons km⁻² yr⁻¹ (3.25 mm yr⁻¹) and 907 tons km⁻² yr⁻¹ (3.42 mm yr⁻¹) respectively, which are far in excess of the global average of 156 tons km⁻² yr⁻¹ (0.58 mm yr⁻¹).     

Discovery of Cinnabar in Soils in Hg Anomalous Zones in City and Town Areas and Their Surroundings and Its Significance

As a result of systematic study on heavy minerals in soils at city and town areas and their surroundings,cinnabar was discovered for the first time in areas of Hg anomalies in China, and it was found that the distribution of cinnabar was basically coincident in scope with that of Hg anomalies, showing that Hg anomalies were‘closely related to cinnabar. This finding provides a theoretical basis for a verification of Hg anomalies in soils in city and town areas and their surroundings, as well as evaluation of its ecological effects, and is significant to revealing the occurrence modes and origin of Hg in soils.     

煤中气孔和镶嵌结构及其在煤变质研究中的意义

河南省禹县、新密和荥巩煤田山西组Ⅱ₁煤的贫煤和无烟煤中,气孔发育。气孔形态有椭圆状（图版1）、圆状及不规则状（图版2）,有的几个气孔连在一起呈大的朵状气孔(图版3)。此外,在荥巩煤田西部无烟煤中还发育有镀嵌结构(图版4)。      

Trends in Analytical Developments and Earth Science Applications in LA-ICP-MS and LA-MC-ICP-MS for 2004 and 2005

This review of laser ablation-inductively coupled plasma-mass spectrometry includes research that employed quadrupole instruments, and single-collector and multicollector magnetic sector field instruments. The most important trend in 2004–2005 was the growing appreciation that small matrix effects in LA-(MC)-ICP-MS need to be addressed in order to produce highly precise and accurate data by the method. The issue is most acute for isotope ratio measurements that require standard-sample-standard bracketing but can also be important for certain elemental analysis. Matrix-dependent elemental and isotopic fractionations were studied from the standpoint of laser-sample interactions and the behaviour of laser-generated particles in the ablation cell, transfer tubing and ICP torch. Innovations in LA-(MC)-ICP-MS involved signal smoothing, in torch laser ablation, on-line isotope dilution and molecular oxide monitoring. Other important research was carried out on the calibration and homogeneity of various reference materials; and the exploration of mature ( in situ U-Pb geochronology) and emerging (apatite fission-track chronometry, U-Th/He thermochronology, boron/strontium/uranium-series isotopic microanalysis) applications in the Earth sciences.     

Regional gravity survey and application in oil and gas exploration in China

Ground gravity survey for regional structure unit delineation and oil and gas exploration in China is addressed in this paper with examples. Gravity survey scales, coverage, technical regulations and achievements at the national level are introduced, including data processing and anomaly interpretation techniques. Bouguer anomalies of terrestrial territories of China and classification of anomalous feature zones are also described; they are well correlated with lithotectonical boundaries, fault zones, and unexposed igneous plutons. Recent study results of petroliferous sedimentary basins are presented as well, including concealed boundaries and major structures of large basins. It is concluded that gravity survey is the most effective and economic method in unveiling unexposed and deep-seated structures, targeting and delineating oil and gas-bearing sedimentary basins, and locating main trap structures within prolific basins in early stage of exploration in China. Suggestions for improving exploration of both conventional and unconventional oil and gas reservoirs in China are also given in the paper.     

Re-Os and Pd-Ag systematics in Group IIIAB irons and in pallasites

Using improved analytical techniques, which reduce the Re blanks by factors of 8 to 10, we report new Re-Os data on low Re and low PGE pallasites (PAL-anom) and IIIAB irons. The new pallasite samples nearly double the observed range in Re/Os for pallasites and allow the determination of an isochron of slope 0.0775 ± 0.0008 (T = 4.50 ± 0.04 Ga, using the adjusted λ¹⁸⁷Re = 1.66 × 10⁻¹¹ a⁻¹) and initial (¹⁸⁷Os/¹⁸⁸Os)₀ = 0.09599 ± 0.00046. If the data on different groups of pallasites (including the “anomalous” pallasites) are considered to define a whole-rock isochron, their formation would appear to be distinctly younger than for the iron meteorites by ∼60 Ma. Five IIIAB irons (Acuna, Bella Roca, Chupaderos, Grant, and Bear Creek), with Re contents ranging from 0.9 to 2.8 ppb, show limited Re/Os fractionation and plot within errors on the IIAB iron meteorite isochron of slope 0.07848 ± 0.00018 (T = 4.56 ± 0.01 Ga) and initial (¹⁸⁷Os/¹⁸⁸Os)₀ = 0.09563 ± 0.00011. Many of the meteorites were analyzed also for Pd-Ag and show ¹⁰⁷Ag enrichments correlated with Pd/Ag, requiring early formation and fractionation of the FeNi metal, in a narrow time interval, after injection of live ¹⁰⁷Pd (t_1/2 = 6.5 Ma) into the solar nebula. Based on Pd-Ag, the typical range in relative ages of these meteorites is ≤10 Ma. The Pd-Ag results suggest early formation and preservation of the ¹⁰⁷Pd-¹⁰⁷Ag systematics, both for IIIAB irons and for pallasites, while the younger Re-Os apparent age for pallasites suggests that the Re-Os system in pallasites was subject to re-equilibration. The low Re and low PGE pallasites show significant Re/Os fractionation (higher Re/Os) as the Re and PGE contents decrease. By contrast, the IIIAB irons show a restricted range in Re/Os, even for samples with extremely low Re and PGE contents. There is a good correlation of Re and Ir contents. The correlation of Re and Os contents for IIIAB irons shows a similar complex pattern as observed for IIAB irons (Morgan et al., 1995), and neither can be ascribed to a continuous fractional crystallization process with uniform solid-metal/liquid-metal distribution coefficients.