www.usgs.gov

Syngenetic Massive Sulfide Studies in East-Central Alaska

Metamorphic stratigraphy in the Alaskan part of the Yukon-Tanana Upland of east-central Alaska is thought to be correlative with Devono-Mississippian rocks in the eastern Alaska Range and the Yukon that host volcanogenic massive sulfide (VMS) deposits. Recent discoveries of VMS deposits in the Finlayson Lake area of central Yukon have increased the potential for similar deposits in Devono-Mississippian metavolcanic rocks in east-central Alaska. In addition, permissive evidence for a correlation of clastic metasedimentary rocks in the northwestern portion of the Yukon-Tanana Upland in Alaska with Devono-Mississippian rocks in the Selwyn Basin (Earn Group) suggests the potential for sedimentary exhalative (sedex), as well as VMS, massive sulfide deposits in the Upland. Although the potential for base metal deposits within these rocks has been recognized by private companies and Native Corporations, little information about the host rocks and the nature of sulfide mineralization in these rocks, particularly those in the Yukon-Tanana Upland, is in the public domain.

The objective of this study is to characterize the tectonic setting, petrogenesis, and metallogeny of the stratiform base metal occurrences and deposits in selected areas of east-central Alaska by integrating existing data from reconnaissance mapping and industry studies with new field, petrographic, isotopic, and geochemical data collected from selected sedex and potential VMS occurrences and deposits and their host lithologies. Broad topics that will be addressed by the study are 1) the characteristics, ages, and geneses of the stratiform occurrences and deposits; 2) the relationship, if any, between the various sedex and VMS occurrences and deposits in east-central Alaska; and 3) the relationship, if any, between the occurrences and deposits in the Yukon-Tanana Upland of east-central Alaska with those in the eastern Alaska Range, the Selwyn Basin, and the Yukon-Tanana terrane in the Canadian Cordillera. Data used to address these topics will include: textural analysis, field relations including structural and kinematic analysis, sulfur and lead isotopes, whole rock geochemistry, carbon-sulfur and iron-sulfur relations, zircon U-Pb crystallization and inheritance ages of metaigneous rocks and detrital ages of metasedimentary rocks, and analysis of fluid inclusion. Drill core samples of sedex-type mineralization from the Chena Slate Belt properties of Sumitomo Metal Mining, Alaska (managed by WMG, Inc.) in the Big Delta quadrangle, has been provided for isotopic and petrologic study. A similar study of drill core from the Lead Creek Pb-Ag-Zn prospect of Ventures Resource Alaska is underway.

A scientific paper that provide the results of syngenetic massive-sulfide studies in east-central Alaska is:

To contact the project chief, email Cynthia Dusel-Bacon (cdusel@usgs.gov).

The URL of this page is http://minerals.usgs.gov/west/syngenms/index.html
Date created: 06/22/1998
Last modified: 02/26/2003