Abstract
Character of alteration and gold mineralization in the northeastern Cassia Mountains, south-central Idaho
Abstracts with programs - Geological Society of America, Vol.32(5), p.39
Geological Society of America, Rocky Mountain Section, 52nd annual meeting
03/2000
Abstract
Paleozoic rocks in the NE Cassia Mountains, immediately south of the Snake River Plain, host alteration and anomalous gold mineralization that are broadly similar in character to Carlin-type deposits. Host rocks in the Roberts Gulch-Buckhorn Canyon area include Permian(?) and Pennsylvanian limestone, sandstone, and siltstone that correlate with the Oquirrh Formation. Limestone and dolomitic limestone are light gray with scattered chert. Siltstone and sandstone form thin-bedded and variably carbonaceous and calcareous units that weather medium to dark brown and yellow to orange in unaltered and altered zones, respectively. The section is overlain by the Miocene Idavada volcanic sequence. Deformational fabrics within the carbonates record a polyphase deformational history. Early formed structures include ductile folds and boudinage within limestone. These fabrics are cut by brittle and ductile shear zones. The deformation is inferred to be related to Sevier and earlier tectonism. All of these fabrics are cut by northwest striking, steeply dipping brittle faults that control the observed alteration and mineralization. These structures parallel the range front normal fault east of the field area and most were reactivated during post-Idavada faulting. The sequence is weakly to strongly altered over an area of approximately 10 square km. Alteration types include structurally controlled silica replacement expressed as red to brown jasperoids, quartz and calcite veining, and clay alteration. Specific alteration of limestone includes vein controlled dolomitization and minor quartz veining. Clastic rocks in the area experienced pervasive argillic alteration, decalcification, and local silicification. Jasperoids consisting of aphanitic quartz, hematite, and jarosite reflect fluid flow along northwest striking high-angle faults. Alteration zones are weakly anomalous in As, Sb, Th, and Hg. Gold mineralization typically occurs within quartz-clay alteration zones adjacent to the jasperoid bodies. The alteration projects beneath the Idavada volcanics both to the northwest and southeast. On the basis of the general similarities with Carlin-type deposits to the south, mineralization in upper Paleozoic rocks of the Cassia Mountains is inferred to record the presence of structurally controlled Carlin-style mineralization in southern Idaho.
Details
- Title: Subtitle
- Character of alteration and gold mineralization in the northeastern Cassia Mountains, south-central Idaho
- Creators
- H. R Smith - University of IdahoS. D AndersonC. I GoddardWilliam C McClellandP. E Isaacson
- Resource Type
- Abstract
- Publication Details
- Abstracts with programs - Geological Society of America, Vol.32(5), p.39
- Conference
- Geological Society of America, Rocky Mountain Section, 52nd annual meeting
- Publisher
- Geological Society of America (GSA)
- ISSN
- 0016-7592
- Alternative title
- Geological Society of America, Rocky Mountain Section, 52nd annual meeting
- Language
- English
- Date published
- 03/2000
- Academic Unit
- Earth and Environmental Sciences
- Record Identifier
- 9984240800202771
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