Athey, J.E., 1999

Characterization of the DAT Zone, eastern Alaska Range, Alaska: A calcic iron (copper-gold) skarn prospect.

Authors:
Athey, J.E.
Publication Date:
1999
Publisher:
University of Alaska Fairbanks
Ordering Info:
Not available
Quadrangle(s):
Gulkana; Mount Hayes
Citation ID:
27454

Bibliographic Reference

Athey, J.E., 1999, Characterization of the DAT Zone, eastern Alaska Range, Alaska: A calcic iron (copper-gold) skarn prospect.: University of Alaska Fairbanks, M.S. thesis, 152 p., illust., maps.

Abstract

The author studied a Cu-Fe-Au prospect in the eastern Alaska Range, Alaska, informally known as 'the DAT Zone'. Previous workers disagreed about the prospect's genesis; my work conclusively shows it to be a calcic iron skarn deposit with late quartz-pyrite-gold mineralization, broadly coeval with the host Pennsylvanian island arc-related volcanic and associated sedimentary rocks. A sericite-quartz-pyrite altered shear yields a ⁴⁰/Ar³⁹Ar age similar to that of a nearby quartz monzodiorite pluton (300 Ma +/- 1 Ma). The skarn consists of andradite extensively retrograded to ferrotremolite, quartz, magnetite, hematite, calcite, and chalcopyrite. Based on alteration pseudomorphs, the prograde assemblage was clinopyrexene with 20-40 %Hd, wollastonite, and andradite. The main-stage fluids were approximately 600^oC moderately oxidized, and extremely saline (>60% NaCl equivalent). This fluid was clearly different from those of volcanogenic massive sulfide, metamorphic, or epithermal deposits. The lack of explosive texture is inconsistent with the DAT Zone as a porphyry copper deposit.