Re-Os SULFIDE (BORNITE, CHALCOPYRITE, AND PYRITE) SYSTEMATICS OF THE CARBONATE-HOSTED COPPER DEPOSITS AT RUBY CREEK, SOUTHERN BROOKS RANGE, ALASKA

New Re-Os data for chalcopyrite, bornite, and pyrite from the carbonate-hosted Cu deposit at Ruby Creek (Bornite), Alaska, show extremely high Re abundances (hundreds of ppb, low ppm) and contain essentially no common Os. The Re-Os data provide the first absolute ages of ore formation for the carbonate-hosted Ruby Creek Cu-(Co) deposit and demonstrate that the Re-Os systematics of pyrite, chalcopyrite, and bornite are unaffected by greenschist metamorphism. The Re-Os data show that the main phase of Cu mineralization predominantly occurred at 384 ± 4.2 Ma, with an earlier phase possibly at ~400 Ma. The Re-Os data are consistent with the observed paragenetic sequence and coincide with zircon U-Pb ages from igneous rocks within the Ambler metallogenic belt, some of which are spatially and genetically associated with regional volcanogenic massive sulfide deposits. The latter may suggest a temporal link between regional magmatism and hydrothermal mineralization in the Ambler district. The utility of bornite and chalcopyrite, in addition to pyrite, contributes to a new understanding of Re-Os geochronology and permits a refinement of the genetic model for the Ruby Creek deposit.

[1]  J. Schneider,et al.  Concordant ages for the giant Kipushi base metal deposit (DR Congo) from direct Rb–Sr and Re–Os dating of sulfides , 2007 .

[2]  R. Creaser,et al.  Assessment of the 187Re decay constant by cross calibration of Re–Os molybdenite and U–Pb zircon chronometers in magmatic ore systems , 2007 .

[3]  D. Morata,et al.  Re–Os isotope systematics for the Lince–Estefanía deposit: constraints on the timing and source of copper mineralization in a stratabound copper deposit, Coastal Cordillera of Northern Chile , 2006 .

[4]  R. Creaser,et al.  Rhenium-Osmium Geochronology of Arsenopyrite in Meguma Group Gold Deposits, Meguma Terrane, Nova Scotia, Canada: Evidence for Multiple Gold-Mineralizing Events , 2005 .

[5]  R. Creaser,et al.  Re-Os sulfide geochronology of the Red Dog sediment-hosted Zn-Pb-Ag deposit, Brooks Range, Alaska , 2004 .

[6]  R. Creaser,et al.  Re-Os geochronology of organic rich sediments: an evaluation of organic matter analysis methods , 2003 .

[7]  D. Hoatson,et al.  Re–Os dating of the Radio Hill Ni–Cu deposit, west Pilbara Craton, Western Australia , 2001 .

[8]  J. Morgan,et al.  Re-Os Dating of Low-Level Highly Radiogenic (LLHR) Sulfides: The Harnäs Gold Deposit, Southwest Sweden, Records Continental-Scale Tectonic Events , 2000 .

[9]  R. Mathur,et al.  Relationship between copper tonnage of Chilean base-metal porphyry deposits and Os isotope ratios , 2000 .

[10]  R. Mathur,et al.  Age and sources of the ore at Tharsis and Rio Tinto, Iberian Pyrite Belt, from Re-Os isotopes , 1999 .

[11]  S. Wood,et al.  Experimental determination of the solubility of ReO2 and the dominant oxidation state of rhenium in hydrothermal solutions , 1999 .

[12]  J. Morgan,et al.  Re-Os ages for Archean molybdenite and pyrite, Kuittila-Kivisuo, Finland and Proterozoic molybdenite, Kabeliai, Lithuania: testing the chronometer in a metamorphic and metasomatic setting , 1998 .

[13]  D. Hoatson,et al.  Application of the Re‐Os isotopic system to the study of Precambrian magmatic sulfide deposits of Western Australia , 1998 .

[14]  J. Chesley,et al.  Re-Os isotope systematics of sulfides from felsic igneous rocks: Application to base metal porphyry mineralization in Chile , 1997 .

[15]  J. Morgan,et al.  Re-Os Ages of Group IIA, IIIA, IVA, and IVB Iron Meteorites , 1996, Science.

[16]  R. Walker,et al.  Carius tube digestion for low-blank rhenium-osmium analysis , 1995 .

[17]  L. Snee,et al.  Structure, metamorphism, and geochronology of the Cosmos Hills and Ruby Ridge, Brooks Range schist belt, Alaska , 1994 .

[18]  M. Hitzman.  Geology of the Ruby Creek copper deposit, southwestern Brooks Range, Alaska , 1986 .

[19]  J. Proffett,et al.  Geology and Mineralization of the Ambler District, Northwestern Alaska , 1986 .

[20]  D. P. Cox,et al.  Geology and sulfide mineralogy of the Number One Orebody, Ruby Creek copper deposit, Alaska , 1986 .

[21]  J. Schmidt.  Stratigraphic setting and mineralogy of the Arctic volcanogenic massive sulfide prospect, Ambler District, Alaska , 1986 .

[22]  D. D. Runnells.  The mineralogy and sulfur isotopes of the Ruby Creek copper prospect, Bornite, Alaska , 1969 .

[23]  D. D. Runnells.  Anthraxolite Derived from Indigenous Organic Matter in Middle Devonian Dolomite, Cosmos Hills, Alaska , 1965 .

[24]  D. D. Vleeschouwer,et al.  Geological Society of America Abstracts with Programs , 2010 .

[25]  B. Kendall,et al.  sedimentary rocks Os geochronology of Precambrian organic-rich 187 Re- 187 Geological Society, London, Special Publications , 2009 .

[26]  B. Kendall,et al.  187Re-187Os geochronology of Precambrian organic-rich sedimentary rocks , 2009 .

[27]  R. Creaser,et al.  Re-Os Geochronology and Systematics in Molybdenite from the Endako Porphyry Molybdenum Deposit, British Columbia, Canada , 2001 .

[28]  G. Wasserburg,et al.  Negative thermal ion mass spectrometry of osmium, rhenium, and iridium , 1991 .

[29]  K. Ludwig.  Calculation of uncertainties of U-Pb isotope data , 1980 .