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The Longview/Lakeview Barite Deposits, Southern National Petroleum Reserve, Alaska (NPRA) - Potential-Field Models and Preliminary Size Estimates

Professional Paper 1760-C

Prepared in cooperation with the U.S. Bureau of Land Management
By:
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Abstract

Longview and Lakeview are two of the larger stratiform barite deposits hosted in Mississippian Akmalik Chert in the Cutaway Basin area (Howard Pass C-3 quadrangle) of the southern National Petroleum Reserve, Alaska (NPRA). Geologic studies for the South NPRA Integrated Activity Plan and Environmental Impact Statement process included an attempt to evaluate the possible size of barite resources at Longview and Lakeview by using potential-field geophysical methods (gravity and magnetics). Gravity data from 227 new stations measured by the U.S. Geological Survey, sparse regional gravity data, and new, high-resolution aeromagnetic data were forward modeled simultaneously along seven profiles perpendicular to strike and two profiles along strike of the Longview and Lakeview deposits. These models indicate details of the size and shape of the barite deposits and suggest thicknesses of 15 to 24 m, and 9 to 24 m for the Longview and Lakeview deposits, respectively. Two groups of outcrops span 1.8 km of strike length and are likely connected below the surface by barite as much as 10 m thick. Barite of significant thickness (>-5 m) is unlikely to occur north of the presently known exposures of the Longview deposit. The barite bodies have irregular (nonplanar) bases suggestive of folding; northwest-trending structures of small apparent offset cross strike at several locations. Dip of the barite is 10 to 25 degrees to the southeast. True width of the bodies (the least certain dimension) is estimated to be 160 to 200 m for Longview and 220 to 260 m for Lakeview. The two bodies contain a minimum of 4.5 million metric tons of barite and more than 38 million metric tons are possible. Grades of the barite are relatively high, with high specific gravities and low impurities. The potential for the Cutaway Basin to host economically minable quantities of barite is uncertain. Heavy-mineral concentrate samples from streams in the area, trace-element analyses, and physicalproperty measurements of bulk samples derived from trenching or drilling would be valuable for future assessment work.

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Additional Publication Details

Publication type:
Report
Publication Subtype:
USGS Numbered Series
Title:
The Longview/Lakeview Barite Deposits, Southern National Petroleum Reserve, Alaska (NPRA) - Potential-Field Models and Preliminary Size Estimates
Series title:
Professional Paper
Series number:
1760
Chapter:
C
Edition:
Version 1.0
Year Published:
2009
Language:
ENGLISH
Publisher:
U.S. Geological Survey
Contributing office(s):
Alaska Science Center
Description:
iv, 29 p.
Larger Work Type:
Report
Larger Work Subtype:
USGS Numbered Series
Larger Work Title:
Studies by the U.S. Geological Survey in Alaska, 2007
Online Only (Y/N):
Y