Integrated Studies of the Genetic Linkages Between Jurassic Porphyry Cu-Au (Mo) and Epithermal Au-Ag deposits in the Toodoggone District of North-Central British Columbia, Canada

S. M. Rowins, P. Duuring, B. S. McKinley, J. M. Dickinson, L. J. Diakow, R. A. Creaser

Research output: Contribution to conferenceAbstract

Abstract

Possible genetic linkages between proximal porphyry Cu-Au (Mo) and epithermal Au-Ag deposits in the Toodoggone district of north-central British Columbia were investigated during a 3-year NSERC-CRD project (2004-2007) by integrating district-scale geological mapping and geochronological studies with detailed deposit models of the key porphyry and epithermal systems. Episodic plutonism from ca. 218 to 190 Ma coincided with the formation of the largest porphyry Cu-Au (Mo) systems from ca. 202 to 197 Ma, with only minor porphyry mineralization occurring from ca. 197 to 194 Ma. The Fin porphyry Cu-Au-Mo deposit differs from the other porphyry systems by having host-rocks with distinctly lower REE and immobile element abundances and an age that is 16 m.y. older than any other porphyry occurrence in the district. Porphyry systems are spatially restricted to exposed Asitka and Takla Group basement rocks, and more rarely, the lowest member of the Hazelton Group (i.e., the ca. 201 Ma Duncan Member). These country rocks are most commonly exposed in the southern half of the district, where high rates of erosion and uplift have resulted in their preferential exposure. In comparison, low- and high-sulfidation epithermal systems are more numerous in the northern half of the district, where younger, overlying Hazelton Group rocks are mainly exposed. Any cogenetic porphyry systems in northern areas are likely to be buried beneath Hazelton Group rocks. High-sulfidation epithermal systems formed at ca. 201 to 189 Ma, whereas low-sulfidation systems developed at ca. 196 to 186 Ma, demonstrating a temporal coincidence with porphyry systems elsewhere in the district. Amongst all studied epithermal systems, the Baker low-sulfidation epithermal deposit displays the strongest demonstrable genetic link with magmatic fluids. Fluid inclusion studies indicate that its ore fluids were hot (>468 C), saline, and deposited metals at depths >2 km. Sulfur, C, O, and Pb isotope data confirm the involvement of a magmatic fluid. In contrast, the Shasta, Lawyers, and Griz-Sickle low-sulfidation epithermal systems do not display a clear association with magmatic fluids. Instead, their fluid inclusion data indicate the involvement of low- temperature (175 to 335 C), low-salinity (1 to 11 equiv. wt. % NaCl) fluids that deposited metals at depths of
Original languageEnglish
Publication statusPublished - 1 May 2009
Externally publishedYes
EventAmerican Geophysical Union Spring Meeting 2009 - Toronto, Canada
Duration: 24 May 200927 May 2009

Conference

ConferenceAmerican Geophysical Union Spring Meeting 2009
CountryCanada
CityToronto
Period24/05/0927/05/09

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