四川力马河镁铁-超镁铁质岩体的地球化学特征及成岩成矿分析

四川会理力马河镍矿是峨眉山大火成岩省最重要的岩浆硫化物矿床之一,成矿岩体为一小型锾铁-超镁铁岩侵入体,由含斜长石的超镁铁岩(包括舍长辉石橄榄岩和斜长橄榄辉石岩)和辉长岩类的镬铁质岩组成.矿床富含硫化物,成矿元素组合为铜、镍,铂族元素含量很低,没有铂族元素的工业富集,是蛾眉山大火成岩省中富铜镍贫铂族元素的代表性岩浆硫化物矿床.本文对力马河镍矿成矿岩体的镁铁、超镁铁岩及矿床中各种硫化物矿石进行了主量元素、微量元素及铂族元素含量分析.分析结果表明,力马河岩体的镁铁、超镁铁岩属拉斑玄武岩成因系列,岩石特征微量元素比值大致与高钛的峨眉山玄武岩相当、与低钛的峨眉山玄武岩有明显区分,但估计原始岩浆强不相容微量元素绝对含量大大低于高钛玄武岩,因此,其成矿岩体不是与一般的低钛或高钛峨眉山玄武岩(不包括苦橄岩在内)直接对应的深成相.岩体超镁铁岩及矿石铂族元素组成特征表现为无钌亏损的型式,钯/铱比值较小、在5左右,也显著不同于一般的峨眉山玄武岩,而类似于峨眉山大火成岩省苦橄岩的铂族元素组成.运用岩石地球化学研究方法计算,原始岩浆为苦橄质成分:MgO含量约17%、SiO2含量约48%.估计原始岩浆形成于130公里左右的深度,由类似于洋岛玄武岩岩浆源区成分的地幔经19%左右的部分熔融形成.超镁铁岩及硫化物矿石铂族元素含量一般在10-9～10-8暑级,铂族元素相对铜镍强烈亏损,铜/钯比值高于原始地幔10～100倍,铜镍铂族元素组成的原始地幔标准化曲线呈铂族元素显著亏损的“U“型.模式分析说明,导致铂族元素亏损的原因是岩浆成矿演化过程中多阶段硫化物熔离作用造成的,早期熔离出来的硫化物被丢失并造成岩浆中铂族元素亏损,其铂族元素亏损后的岩浆(第)二次硫化物熔离富集形成铂族元素亏损的矿石.     

个旧锡矿区围岩介质成矿地球化学作用

对碳酸盐地层的研究发现，个旧锡矿区围岩介质和地球化学作用对矿床的成因影响很大、联系密切，有明显的成矿控制作用。     

辽西100Ma火山事件的动力学过程及其构造背景

通过辽西及邻区106Ma 来源于软流圈亏损地幔玄武岩的年代学及玄武岩底部不整合面的研究,认识到:(1)这一时期伴随岩石圈地幔物质的更新,存在着"岩浆间隙"和强烈构造运动的现象,从而推断软流圈底辟体上涌、岩石圈减薄、岩浆活动间隙、强烈构造运动这四者之间的因果关系,其中被软流圈熔体带上来的物质和热能是主导因素,岩石圈减薄是关键;(2)106Na 与116Ma、93Ma、80Ma、45Ma 火山岩之间的对比研究,表明106Ma 开始的岩石圈地幔的更新是一个漫长的不可逆转的过程。(3)通过本区火山岩的演变与相邻大洋板块同期热扩张历史的对比研究,推测晚中生代(120～80Ma)大洋与大陆岩石圈板块同步的演化特征可能反映了它们共同受到岩石圈板块之下同一深部热扰动的控制。     

Influence of metal oxides in the colorimetric determination of acid volatile sulfide in sediments

The sediment of Lagoa dos Patos‐MS, Brazil, was investigated to verify the influence of metal sulfides and oxyhydroxides of Mn and Fe on the heavy metal availability. The spectrophotometric method of methylene blue was used, with 8 interlinked tubes containing the samples with SnCl₂, where N₂ was introduced to release the H₂S extracted with 6.0 mol L^–1 HCl, and trapped in 0.05 M NaOH solution. The influence of SO₄^2–, Mn(IV) and Fe(III) oxyhydroxides was investigated with samples constituted by a mixture of MnO₂; Na₂SO₄; FeCl₃, and sediments. The presence of SnCl₂ was very important to avoid the interferences of iron and manganese oxyhydroxides. The method of standard addition was applied and the efficiency was (100.8 ± 9.4)%. The ratio among the quantities of metals potentially available and the acid volatile sulfide (AVS) indicate that the system presents small metals availability to the benthic community, by the existence of sulfide capable to immobilize the metal as insoluble sulfide.     

DMS and SO2 Measurements in the Tropical Marine Boundary Layer

Dimethyl sulfide (DMS) and sulfur dioxide (SO₂) mixing ratios were measured in the boundary layer on Oahu, Hawaii in April and May 2000. Average DMS and SO₂ levels were 22 ± 7 (n = 488) pmol/mol and 23 ± 7 (n = 471) pmol/mol respectively. Anti-correlated DMS and SO₂ diurnal cycles, consistent with DMS + OH oxidation were observed on most days. Photochemical box model simulations suggest that the yield of SO₂ and total SO₂ sink are ∼85% and ∼2 × 10⁴ molec cm^{− 3} s^{− 1} respectively. On several days the rate of decrease in DMS and increase in SO₂ levels in the early morning were larger that predicted by the model. Dynamical and chemical causes for the anomalous early morning data are explored.     

新疆昆仑式火山岩型块状硫化物铜矿床及成矿地质环境

新疆西昆仑奥依塔克-恰尔隆拗陷带内阿克塔什-萨落依成矿带发现多处火山岩型块状硫化物铜矿床。这些矿床产在石炭系双峰式火山岩系之内，沿着下石炭统基性火山岩和上石炭统酸性火山岩两个层位产出，分别以玄武岩和流纹岩为容矿主岩，可以明显地分成基性火山岩型和酸性火山岩型两种类型。矿石主成矿元素均以铜为主，含少量的锌，几乎不含铅，矿床类型属于铜型。这些基性火山岩型和酸性火山岩型矿床被统称为昆仑式火山岩型块状硫化物铜矿床。根据矿床产出地质环境、双峰式火山岩系、沉积建造以及火山岩地球化学特征，推断昆仑式火山岩型块状硫化物铜矿床最可能形成于泥盆纪-石炭纪弧后拉张构造环境。     

铜陵矿集区铜金矿床叠加改造过程中的排金效应

通过对铜陵地区各矿田内的矿床的观察发现，它们均含铜、金，但各矿床含铜、金的差异性比较大。该区海西期同生沉积的SEDEX型块状硫化物矿床和燕山期岩浆热液矿床的成矿物质来源具有二元性。在峙门口(铜金)硫铁矿、水竹岭金铜矿和虎山金矿(牛山硫铁矿)等较为典型的海西期块状硫化物矿床中，可圈出独立的金(铜)矿体；以凤凰山铜矿田、小金山金矿、笠帽山金矿等为典型代表的燕山期岩浆热液矿床，也具有较高的金、铜品位，可形成工业矿体。但无论是海西期同生沉积矿床还是燕山期岩浆热液矿床，规模都比较小。有些矿床尽管存在海西期同生沉积成矿作用和燕山期岩浆热液成矿作用，但铜、金分配明显不同，品位差异悬殊。导致水平方向或垂直方向上铜、金分配差异的原因可归结为矿床叠加改造过程中的温度场控制的“排金效应”，形成“下铜上金”、“内铜外金”(储国正等，1992)的矿床分布格局。     

Subsea-floor replacement in volcanic-hosted massive sulfide deposits

Recent research on volcanic-hosted massive sulfide (VMS) deposits indicates that syngenetic subsea-floor replacement ores form an important component of many deposits. In the context of VMS deposits, subsea-floor replacement can be defined as the syn-volcanic formation of sulfide minerals within pre-existing volcanic or sedimentary deposits by infiltration and precipitation in open spaces (fractures, inter- and intra-granular porosity) as well as replacement of solid materials.There are five criteria for distinguishing subsea-floor replacement in massive sulfide deposits: (1) mineralized intervals are enclosed within rapidly emplaced volcanic or sedimentary facies (lavas, intrusions, subaqueous mass-flow deposits, pyroclastic fallout); (2) relics of the host facies occur within the mineral deposit; (3) replacement fronts occur between the mineral deposit and the host lithofacies; (4) the mineral deposit is discordant to bedding; and (5) strong hydrothermal alteration continues into the hanging wall without an abrupt break in intensity. Criteria 1–3 are diagnostic of replacement, whereas criteria 4 and 5 may suggest replacement but are not alone diagnostic. Because clastic sulfide ores contain accessory rock fragments collected by the parent sediment gravity flow(s) during transport, criteria 2 can only be applied to massive, semi-massive, disseminated or vein style deposits, and not clastic ores.The spectrum of VMS deposit types includes deposits that have accumulated largely subsea-floor, and others in which sedimentation and volcanism were synchronous with hydrothermal activity, and precipitation of sulfides occurred at and below the sea floor over the life of the hydrothermal system. Deposits that formed largely subsea-floor are mainly hosted by syn-eruptive or post-eruptive volcaniclastic facies (gravity flow deposits, water-settled fall, autoclastic breccia). However, some subsea-floor replacement VMS deposits are hosted by lavas and syn-volcanic intrusions (sills, domes, cryptodomes). Burial of sea-floor massive sulfide by lavas or sediment gravity flow deposits can interrupt sea-floor mineralization and promote subsea-floor replacement and zone-refining.The distance below the sea floor at which infiltration and replacement took place is rarely well constrained, with published estimates ranging from less than 1 to more than 500 m, but mainly in the range 10–200 m. The upper few tens to hundreds of metres in the volcano-sedimentary pile are the favoured position for replacement, as clastic facies are wet, porous and poorly consolidated in this zone, and at greater depths become progressively more compacted, dewatered, altered, and less amenable to large scale infiltration and replacement by hydrothermal fluids. Furthermore, sustained mixing between the upwelling hydrothermal fluid and cold seawater is regarded as a major cause of sulfide precipitation in VMS systems, and this mixing process generally becomes less effective with increasing depth in the volcanic pile.The relative importance of subsea-floor replacement in VMS systems is related principally to four factors: the permeability and porosity patterns of host lithofacies, sedimentation rate, the relative ease of replacement of host lithofacies (especially glassy materials) and early formed alteration minerals during hydrothermal attack, and physiochemical characteristics of the hydrothermal fluid.     

大洋多金属结核和深海沉积物标准物质中铂族元素的中子活化分析

采用镍锍试金预富集中子活化分析方法,测定了大洋多金属结核标准物质ＧＳＰＮ２、ＧＳＰＮ３和深海沉积物标准物质ＧＳＭＳ２、ＧＳＭＳ３中的铂族元素;根据大洋样品成分特征,对常规的镍锍试金配方和熔炼条件作了改善;计算了活化分析中的铂族元素干扰核反应,校正了Ａｕ对Ｐｔ的二级干扰;选用羰基化镍粉配料,降低了铂族元素空白值。用国家一级标准物质ＧＢＷ０７１０２作了对照分析,结果与标准值相符。     

滇东南喷流沉积块状硫化物特征与矿床成因

滇东南一些著名的大型－超大型锡多金属矿床,如个旧锡矿和都龙锡矿,白牛厂大型银,锡多金属矿床下部均有燕山期花岗岩发育,因此,个旧和都龙锡多金属矿床大多数人认为是岩浆热液矿床。笔者对上述三个矿床的矿石矿物组构、成分以及它们的共生组合关系进行了系统研究,发现了大量海底喷流沉积结构构造,值得一提的是在岩体接触带附近的块状硫化物矿体中发现了缅状结构和丝状客形虫等证据,而这些矿体曾被认为是典型的岩浆热液成因,