An Overview of the Structure, Stratigraphy, and Zn-Pb-Ag Deposits of the Red Dog District, Northwestern Alaska
Published:January 01, 2013
Scott K. Blevings, Jamie L. Kraft, James U. Stemler, Tom E. Krolak, 2013. "An Overview of the Structure, Stratigraphy, and Zn-Pb-Ag Deposits of the Red Dog District, Northwestern Alaska", Tectonics, Metallogeny, and Discovery: The North American Cordillera and Similar Accretionary Settings, M. Colpron, T. Bissig, B. G. Rusk, J. F. H. Thompson
Download citation file:
The world-class Zn-Pb-Ag deposits of the Red Dog district, Alaska, occur in severely shortened, late Paleozoic sedimentary rocks of the western Brooks Range fold and thrust belt. Red Dog-style strata-bound mineralization occurs within a localized Mississippian black shale facies of the Lisburne Group informally termed the Ikalukrok unit. Prior work has developed paleogeographic models in which the Ikalukrok unit formed in a starved, second-order basin flanked by carbonate platforms. Collision with and northward (modern coordinates) obduction of the oceanic Angayucham terrane telescoped Devonian to Early Jurassic passive margin sediments along thrust faults with displacements ranging from meters to tens or hundreds of kilometers. The most significant thrusts bound allochthons that juxtapose coeval stratigraphy from previously widely separated parts of the former continental margin. Thrusts within the allochthons created structurally and stratigraphically defined thrust plates and subplates, which are in turn deformed internally by smaller faults and associated folds. Steeply dipping extensional faults cut all compressional structures in the district.
The Red Dog mine area and Anarraaq deposits are highly enriched in Zn and Pb owing to the superposition of as many as four phases of sulfide mineralization through carbonate replacement, brecciation, silicification, and veining. Barite and secondary silica are pervasive and intimately associated with base-metal mineralization in the mine area deposits. A giant barite body occurs in the structural hanging wall of the Anarraaq deposit but is spatially separated from it. The Ikalukrok unit hosts other strata-bound Zn-Pb-Ag deposits and occurrences in the Red Dog district that are referred to herein as laminated deposits. Sulfides within laminated deposits such as Su and Lik are typically laminated and brecciated. These deposits lack evidence of associated barite or widespread, multiphase massive base-metal sulfides, which form the high-grade cores of the mine area and Anarraaq deposits. We suggest that differences in character of Zn-Pb-Ag deposits in the Red Dog district can be attributed to variability in the original composition of the Ikalukrok unit host and the location of the deposits within the original subbasin.
Figures & Tables
Tectonics, Metallogeny, and Discovery: The North American Cordillera and Similar Accretionary Settings
The northern Pacific Rim—for the purposes of this contribution—comprises the Mesozoic and Cenozoic magmatic-arc and associated terranes of eastern China, Korea, Japan, the Russian Far East, Alaska, Yukon, British Columbia, the western United States, and Mexico. This ~1,800-km-long segment of the Pacific Rim is marked by a broad spectrum of metallogenic environments and mining jurisdictions, which combine to dictate where and how exploration is conducted and the overriding character of any resulting discoveries.
This summary report commences with a brief metallogenic overview of the northern Pacific Rim, with particular attention paid to the world-class Mesozoic and Cenozoic ore deposits that define the region’s premier metallogenic provinces. This is followed by a summary of the relative attractiveness of the region’s various mining jurisdictions, as recorded by recent exploration activity. The major discoveries made along the northern Pacific Rim, particularly during the past half century, are then placed in this metallogenic and regulatory context as a basis for determining the successful exploration methodologies employed. This discovery track record is then used to predict what the future of exploration in this vast and varied region may hold.
Much of the northern Pacific Rim, from eastern China and the Russian Far East in the northwest through Alaska to western parts of Canada, the United States, and Mexico in the southeast (Fig. 1), is characterized by a complex array of oceanic, accretionary prism, magmatic arc, and back-arc basin terranes and associated microcontinental blocks accreted to the North China, Siberian, Hyperborean, and North American cratons, mainly during Mesozoic times (Coney et al., 1980; Campa and Coney, 1983; Kojima, 1989; Nokleberg et al., 2005; Yakubchuk, 2009). The metallogeny of these tectonic collages is dictated by various combinations of pre-, syn-, and postaccretion ore-forming events, the last of which are generally preeminent, except in British Columbia (Nokleberg et al., 2005; Nelson and Colpron, 2007).
Although the Meso-Cenozoic metallogeny of the northwestern and northeastern Pacific quadrants displays some similarities, it is the contrasts that are most marked. The main contrasts stem from the preeminence of tin, tungsten, and antimony in eastern China, Korea, Japan, and the Russian Far East and of copper and silver in Western Canada, the conterminous United States, and Mexico. Nonetheless, both the northwestern and northeastern Pacific quadrants are exceptionally well endowed with gold and molybdenum deposits. The northeasternmost Russian Far East, Alaska, and Yukon Territory display elements of both northwestern and northeastern Pacific metallogeny (Fig. 1). These metallogenic contrasts between the northwestern and northeastern quadrants result in China being the world’s leading producer of tungsten, tin, bismuth, and antimony, mostly from its eastern Mesozoic metallogenic province.