GOLD AND ARSENIC IN IRON SULFIDES FROM SEDIMENT-HOSTED DISSEMINATED GOLD DEPOSITS - IMPLICATIONS FOR DEPOSITIONAL PROCESSES

被引:205
作者
AREHART, GB
CHRYSSOULIS, SL
KESLER, SE
机构
[1] UNIV MICHIGAN,DEPT GEOL SCI,ANN ARBOR,MI 48109
[2] UNIV WESTERN ONTARIO,SURFACE SCI WESTERN,LONDON N6A 5B8,ON,CANADA
来源
ECONOMIC GEOLOGY AND THE BULLETIN OF THE SOCIETY OF ECONOMIC GEOLOGISTS | 1993年 / 88卷 / 01期
关键词
D O I
10.2113/gsecongeo.88.1.171
中图分类号
P3 [地球物理学]; P59 [地球化学];
学科分类号
0708 ; 070902 ;
摘要
Secondary ion microscopic elemental distribution maps and quantitative measurements of Au and As concentrations in samples from five sediment-hosted disseminated gold deposits in Nevada present a consistent picture of the location and nature of gold in these samples. Gold is present in arsenian pyrite that forms overgrowth rims on, and narrow veinlets in, gold-free pyrite (and possibly other minerals, but only to a minor extent). Auriferous overgrowth rims that may exhibit compositional zoning, either simple or oscillatory, range from approximately 25 mum in thickness to the limits of microscopic resolution. Because all of the observed gold-bearing pyrite contains sufficient As to be metastable (i.e., in excess of approximately 0.5%), it is suggested that small native gold grains occasionally observed in unweathered sediment-hosted disseminated gold ores resulted from exsolution of gold from the arsenian pyrite lattice. Available evidence suggests that gold in arsenian pyrite is most likely present as a charged species (Au+3) and that gold probably was deposited with arsenic as coupled solid solution substitutions in pyrite. The codeposition of gold and arsenic in pyrite in these and many other deposits may be a function of a redox reaction involving oxidation of gold and concurrent reduction of arsenic. Commonly proposed reactions involving gold deposition in sediment-hosted disseminated gold deposits usually involve gold precipitation as a neutral species from a bisulfide complex. It is proposed that such reactions are inappropriate for gold deposition in arsenian pyrite but that reactions involving oxidation of gold and concurrent reduction of arsenic are probably more appropriate. Mechanisms effecting gold deposition as native metal also will effect deposition as Au+3 if it is deposited along with arsenic (in either arsenopyrite or arsenian pyrite).
引用
收藏
页码:171 / 185
页数:15
相关论文
共 41 条
  • [1] EVIDENCE FOR THE SUPERGENE ORIGIN OF ALUNITE IN SEDIMENT-HOSTED MICRON GOLD DEPOSITS, NEVADA
    AREHART, GB
    KESLER, SE
    ONEIL, JR
    FOLAND, KA
    [J]. ECONOMIC GEOLOGY AND THE BULLETIN OF THE SOCIETY OF ECONOMIC GEOLOGISTS, 1992, 87 (02): : 263 - 270
  • [2] AREHART GB, 1993, GEOCHIM COSMOCHIM AC
  • [3] AREHART GB, 1993, EC GEOL, V88
  • [4] AREHART GB, 1991, GEOL SOC AM ABSTR, V23, P228
  • [5] Bagby WC., 1985, GEOLOGY GEOCHEMISTRY, V2, P169, DOI [10.5382/Rev.02.08, DOI 10.5382/REV.02.08]
  • [6] HIGH-RESOLUTION MICROSCOPY OF GOLD IN UNOXIDIZED ORE FROM THE CARLIN MINE, NEVADA
    BAKKEN, BM
    HOCHELLA, MF
    MARSHALL, AF
    TURNER, AM
    [J]. ECONOMIC GEOLOGY, 1989, 84 (01) : 171 - 179
  • [7] BAKKEN BM, 1986, GOLD 86, P488
  • [8] BAKKEN BM, 1991, GEOL SOC AM ABSTR, V23, P228
  • [9] ARSENIC GEOCHEMISTRY IN GEOTHERMAL SYSTEMS
    BALLANTYNE, JM
    MOORE, JN
    [J]. GEOCHIMICA ET COSMOCHIMICA ACTA, 1988, 52 (02) : 475 - 483
  • [10] BIRAK DJ, 1985, US GEOL SURVEY B, V1646, P95