@article{fdi:010089766,
  title = {{O}rigin and evolution of gold-bearing fluids in a carbon-rich sedimentary basin : {A} case study of the {A}lgamarca epithermal gold-silver-copper deposit, northern {P}eru},
  author = {{G}aldos, {R}. and {V}allance, {J}. and {B}aby, {P}atrice and {S}alvi, {S}. and {S}chirra, {M}. and {V}elasquez, {G}. and {V}iveen, {W}. and {S}oto, {R}. and {P}okrovski, {G}. {S}.},
  editor = {},
  language = {{ENG}},
  abstract = {{S}ediment-hosted gold deposits account for the major part of economic gold in the {E}arth's crust. {H}owever, the origin of the gold-bearing fluid and its evolution in sedimentary basins in the presence of organic carbon and its metamorphosed products such as graphite are poorly known. {I}n an attempt to clarify these issues, we performed an integrated mineralogical, geochemical, and fluid-inclusion study of the {A}lgamarca epithermal {A}u-{A}g-{C}u deposit, hosted by {M}esozoic sediments corresponding to an over-mature petroleum system within the {M}ara & ntilde;& oacute;n fold and thrust belt (northern {P}eru). {R}esults show that mineralization started with a pre-gold stage characterized by quartz veins containing gold-poor pyrite and chalcopyrite. {M}ost gold was deposited afterwards, during the main gold stage in an "invisible" form within arsenian pyrite, followed by minor visible native gold with sulfosalts and chalcopyrite at a later stage. {F}luid inclusions in quartz from the pre-gold and gold stages show features analogous to those observed in porphyry {C}u-{A}u systems such as vapor-liquid immiscibility, enrichment in {K}, {R}b, {C}u, {A}s, and {S}b, a wide range of salinity (5-35 wt% {N}a{C}l eq.), and similar elemental (atomic) ratios ({Z}n/{P}b similar to 4, 0.1 < {K}/{N}a < 5, {B}r/{C}l similar to 0.06), all consistent with a fluid of magmatic origin. {I}n addition, the fluid inclusions from the pre-gold stage are highly enriched in {CO}2 (similar to 60 mol% in gas phase), {CH}4 (similar to 10 mol%) and {H}2{S} (similar to 30 mol%). {S}uch high volatile contents are rather unusual for typical porphyry-epithermal systems and likely reflect reactions between the magmatic fluid and carbon-bearing sediments. {T}his conclusion is independently supported by the temperature values of graphite metamorphic peak determined by {R}aman spectroscopy, which are similar to those derived by fluid-inclusion microthermometry in quartz veins. {O}ur findings imply that strong interactions of magmatic fluid with carbonaceous matter favored gold transport through the sedimentary basin and its subsequent concentration in arsenian pyrite. {F}urthermore, our results point to a possible presence of porphyry-style mineralization beneath the sedimentary sequence hosting the epithermal {A}lgamarca deposit, thereby providing new potential for exploration.},
  keywords = {{E}pithermal deposit ; {S}edimentary basin ; {A}rsenian pyrite ; {I}nvisible gold ; {G}raphite ; {F}luid inclusion ; {PEROU}},
  booktitle = {},
  journal = {{O}re {G}eology {R}eviews},
  volume = {166},
  numero = {},
  pages = {105857 [27 ]},
  ISSN = {0169-1368},
  year = {2024},
  DOI = {10.1016/j.oregeorev.2023.105857},
  URL = {https://www.documentation.ird.fr/hor/fdi:010089766},
}