• Paleozoic and Mesozoic volcanic-hosted massive sulfide deposits of the BC Cordillera. Research on: volcanic stratigraphy; geometry and geochemistry of alteration zones; and mass transfer during hydrothermal alteration (at the Myra Falls , Tulsequah Chief, Eskay Creek, Hidden Creek, Kutcho Creek, Seneca and other deposits of BC). Development of stratigraphic and lithogeochemical exploration techniques for massive sulfide deposits in volcanic belts.

  • Precambrian volcanic-hosted massive sulfide deposits of the Noranda mining camp. Work as above but in greenstone belts >2.5 gy. Main deposits studied to date include the Horne, Ansil, Mobrun, Aldermac, Norbec, Delbridge and Corbet deposits. Also several studies of volcanic terranes in Timmins regions in last four years.

  • Hydrothermal alteration of oceanic crust and Phanerozoic ophiolites, and assessment of hydrothermal input into modern and ancient oceans. Metal sulfide and oxide deposits at spreading axes and in ophiolite complexes. Stratigraphy, sedimentology and geochemistry of:

    • Deep-sea metalliferous and pelagic sediments in modern oceans, in oxic versus anoxic settings, and their vertical and lateral relation to oceanic basement. The main field areas are, respectively, the eastern Pacific ocean, and the Atlantis II Deep metal deposits in the Red Sea.

    • Phanerozoic ophiolite-sediment sequences in orogenic belts of the western Tethyan Apennine-Alpine chain and the Caledonides of Scotland and Newfoundland.
  • Stratigraphy and geochemistry of volcanic rocks, turbidites, iron formations, and massive sulfide deposits in the Archean Wabigoon-Wawa terrains in western Ontario, and the Lower Proterozoic iron formations of the Labrador Trough. Geochemistry of chemical sediments: deep-water sequences (Michipicoten) and shallow-water sequences (Gunflint).

    Recognition of variations with time in the hydrothermal input to Precambrian oceans, as assessed from rare-earth element and sulfur and Nd-isotopic studies of chemical precipitates. Paleoenvironmental interpretation based on facies changes in clastic and chemical sediments.

  • Experimental studies of water-rock interaction under the conditions of hydrothermal alteration and mineralization. Mass transfer processes and the behaviour of various mobile and rare-earth elements in different alteration zones. Experimental solubility studies of Zn and Pb sulfides as applied to problems of ore transport and deposition in syngenetic and epithermal deposits (particularly seafloor hydrothermal systems and Mississippi Valley-type ore deposits in carbonate sequences). Solubilities of metal sulfides (As, Hg, Bi) in low- to moderate-temperature hydrothermal systems as applied to epithermal ore deposits and modern geothermal systems.

    Significance

    Studies on massive sulfide deposits and their alteration zones in the Abitibi greenstone belt and the Cordillera of British Columbia have determined:

    • the primary igneous composition of host volcanics ranging from unimodal through to differentiated basalt-andesite-dacite-rhyolite sequences;

    • the relation of orebody and stockwork mineralization to volcanic facies and paleotopographic controls;

    • the type and degree of alteration in polymodal volcanics.
    We have developed detailed, rigorous chemical methods for refining volcanic chemostratigraphy, and for recognizing original rock compositions in a variety of alteration zones (including extreme alteration). This allows reliable stratigraphic correlations between drill-holes in an exploration program. Trends within hydrothermal alteration zones can be recognized using mass changes that can be calculated from chemical data. These methods also can be applied to regional scale problems of terrane selection and recognition of specific lithological units and types of alteration. These types of studies have also been recently applied to VMS deposits and host terranes in other types of regional settings, including deposits in island arcs such as the Philippines (Barrett, 1995a, 1996), and deposits in rifted continental margin settings such as at Parys Mountain in the Welsh Basin (Barrett, 1995a) and in the Ambler Range of Alaska (Barrett and MacLean, 1996).

    Studies of mineralized Precambrian iron-formations allow determination of hydrothermal input during chemical sedimentation in volcanic versus sedimentary, and deep versus shallow oceanic settings. Interpretations are aided by ongoing studies of oceanic precipitates dispersed about a variety of hydrothermal vent settings in the eastern Pacific and the Atlantis II Deep of the Red Sea. The goals are to locate the sources of hydrothermal discharge in basins influenced by submarine chemical precipitation, in order to locate base-metal deposits. This is done by assessing sedimentological trends, and by determining clastic versus hydrothermal contributions of elements based on lithogeochemistry, including Nd-Sr-Pb isotopes and rare-earth elements. Metal sulfide solubilities in experimental hydrothermal solutions quantify metal behavior in these and other ore-forming systems, e.g. in geothermal systems on-land and at deep-marine, oceanic spreading axes.




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