Precambrian geology and bedded iron deposits of the southwestern Ruby Range, Montana
The Precambrian crystalline rocks of the southwestern Ruby Range, an area of about 100 square miles, can be divided roughly into three northeast-trending belts, progressively younger to the west.The oldest and most easterly belt consists of an ill-defined sequence of Early( ) or Middle( ) Archean older gneiss and schist that underlies, with structural conformity, a central belt underlain in turn by a rudely tabular mass of Middle or late Archean quartzofeldspathic gneiss that forms the crest of the range for much of its length. This quartzofeldspathic gneiss forms a basement complex to an overlying sequence of metasedimentary strata that make up the most westerly of the three belts. The Middle or Late Archean metasedimentary sequence, here named the Christensen Ranch Metasedimentary Suite, consisted originally of miogeoclinal-type sedimentary rocks, now represented by dolomite marble, diopsidic and hornblendic gneiss and schist, quartzite, mica and garnet schist, and banded iron-formation. Amphibolite of Middle or Late Archean age is an abundant rock type, occurring as generally conformable screens and sheets, some as much as several thousand feet in thickness, in each of the three main rock groups. Known or potential mineral resources include talc, graphite, and banded iron-formation. The iron-formation has been explored extensively in the Carter Creek area; these deposits are estimated to contain about 95 million tons of rock containing 28-29% iron recoverable as magnetite. The Kelly iron deposit is in the northeastern part of the Ruby Range. The iron-formation in this upthrust block has been explored by test pits and drill holes, but despite a favorable composition, the economic potential is low; deposits are estimated to be about 15 million tons containing 33% iron recoverable as magnetite.
- OSTI ID:
- 6317498
- Journal Information:
- United States Geological Survey, Professional Paper; (USA), Vol. 1495
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
IRON ORES
RESOURCE POTENTIAL
MONTANA
MINERAL RESOURCES
AGE ESTIMATION
COAL DEPOSITS
DOLOMITE
GEOLOGIC DEPOSITS
GEOLOGIC HISTORY
GEOLOGY
GNEISSES
GRAPHITE
LITHOLOGY
MARBLE
MICA
OROGENESIS
PLUTONIC ROCKS
QUARTZITES
SCHISTS
SEDIMENTARY ROCKS
STRATIGRAPHY
ALKALINE EARTH METAL COMPOUNDS
CALCIUM CARBONATES
CALCIUM COMPOUNDS
CARBON
CARBON COMPOUNDS
CARBONATE MINERALS
CARBONATES
ELEMENTAL MINERALS
ELEMENTS
FEDERAL REGION VIII
IGNEOUS ROCKS
MAGNESIUM CARBONATES
MAGNESIUM COMPOUNDS
METAMORPHIC ROCKS
MINERALS
NONMETALS
NORTH AMERICA
ORES
OXYGEN COMPOUNDS
RESOURCES
ROCKS
USA
580000* - Geosciences