1995/01/01 by Glen R. Himmelberg, R.A. Loney · 1 citation
Earth and Planetary Sciences · Computer Science · #Geological Studies and Exploration #Geological and Geochemical Analysis #Geochemistry and Geologic Mapping #Mafic #Petrogenesis #Ultramafic rock #Geology #Geochemistry #Layered intrusion #Petrology #Basalt
paper · pdf · doi:10.3133/pp1564
openalex publication_date 1995/01/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/14
Alaskan-type ultramafic-mafic intrusions occur along a belt that extends from Duke Island to Klukwan in southeastern Alaska and fall into two age groups-400 to 440 Ma; and 100 to 118 Ma. Most of the intrusions occur in the Alexander terrane or in the Gravina overlap assemblage, but they are not restricted to these terranes. The Alaskan-type ultramafic bodies range in size from sills only a few meters thick to intrusions about 10 km in maximum exposed dimension. Most of the bodies consist of magnetite-bearing hornblende clinopyroxenite or hornblendite, however many of the larger ones also include dunite, wehrlite, olivine clinopyroxenite, and, in some cases, gabbro. The Blashke Islands and Union Bay bodies are markedly concentrically zoned; dunite in the core is surrounded progressively outward by wehrlite, olivine clinopyroxenite, clinopyroxenite, hornblende clinopyroxenite, and gabbro. In the other large bodies, crude zoning may be present, but individual zones are discontinuous or missing entirely.