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Robert G. Luedke

Publications and source records attributed to Robert G. Luedke.

At least 19 recordsLinked to original sources
USGS2008

Geology and ore deposits of the Uncompahgre (Ouray) Mining District, Southwestern Colorado

The Uncompahgre mining district, part of the Ouray mining district, includes an area of about 15 mi 2 on the northwestern flank of the San Juan Mountains in southwestern Colorado from which ores of gold, silver, copper, lead, and zinc have had a gross value of $14 to 15 million. Bedrock within the district ranges in age from Proterozoic to Cenozoic. At least three major uplifts of the ancestral San Juan Mountains occurred during the Proterozoic and at the close of the Paleozoic and Mesozoic, respectively. The last event, known as the Laramide orogeny, locally was accompanied by extensive intrusion of igneous rocks. The principal ore deposits of the district were associated with crosscutting and laccolithic intrusions of porphyritic granodiorite formed during the Laramide orogeny. The ores were deposited chiefly in Paleozoic and Mesozoic sedimentary strata. Ore deposits range from low-grade, contact-metamorphic through pyritic base-metal bodies containing silver and gold tellurides and native gold to silver-bearing lead-zinc deposits. Ore deposition was largely controlled by structural trends and axes of uplift established during Paleozoic deformation, and also in part by structural lines established during the Proterozoic. There are two main structural axes in the district: (1) a north-northwest-trending axis of uplift, called the Uncompahgre axis, and (2) an intrusive axis of northeastward trend. The two axes intersect near the center of eruptive activity and divide the district into four structural sectors. Sources of the ore-forming fluids lie along the northeast-trending intrusive zone and appear to be related genetically to the igneous rocks. Contact-metamorphic deposits and most of the pyritic gold-bearing deposits were found in the central parts of the district. The silver-lead-zinc deposits were found chiefly in the northern and southern sectors of the district. Ore deposition was controlled by nearness to the intrusive contacts, nearness to zones of shallow tensional fractures, and other factors. The largest and highest grade deposits were either mostly developed or nearly exhausted at the time of our studies; they occurred in a zone near the Uncompahgre axis.

Colorado↗
USGS1974

Relation of mineralization to calderas in the San Juan volcanic field, southwestern Colorado

A review of the calderas in the San Juan volcanic field, southwestern Colorado, indicates that lead, zinc, copper, gold, and silver mineralization took place in and near calderas which had complex histories of postsubsidence intrusive and extrusive igneous activity. Most known ore occurs in veins that follow fractures formed during the different caldera cycles, but some intrusive bodies were extensively mineralized and possibly may host disseminated, porphyry-type deposits. The mineral deposits seem to be related most commonly to the youngest and most highly differentiated late intrusives of a caldera cycle.

Colorado↗
USGS1973

Revised volcanic history of the San Juan, Uncompahgre, Silverton, and Lake City calderas in the western San Juan Mountains, Colorado

The sequence of mid-Cenozoic volcanic events in the western San Juan Mountains is closely analogous to that elsewhere in the San Juan volcanic field. The Lake Fork, Picayune, and San Juan Formations were erupted from a cluster of central volcanoes from 35 to 30 m.y. ago, when dominant activity shifted to more silicic ash-flow eruptions with accompanying caldera collapses. The Uncompahgre and San Juan calderas, each about 20 km across, formed mainly from eruption of the 28-m.y.-old Sapinero Mesa Tuff. Collapse occurred concurrently with eruption, and intracaldera tuffs accumulated to a thickness of more than 700 m. Both calderas were resurgently domed together; the northeast-trending Eureka graben formed along the distended crest of that dome. The Uncompahgre caldera was then flooded by several 27- to 28-m.y.-old ash-flow sheets from easterly sources, and also by one apparently erupted from the Silverton caldera nested within the older San Juan caldera. The Lake City caldera, located within the older Uncompahgre caldera, formed about 22.5 m.y. ago in response to eruption of the Sunshine Peak Tuff.

Colorado↗
USGS1963

Geology of the Capitol Reef area, Wayne and Garfield Counties, Utah

The Capitol Reef area includes about 900 square miles in western Wayne and north-central Garfield Counties, Utah. It is along the border between the High Plateaus of Utah and the Canyon Lands sections of the Colorado' Plateaus province. Capitol Reef National Monument is in the eastern part of the mapped area.

Utah↗
USGS1953

Stratigraphy and structure of the Miners Mountain area, Wayne County, Utah

The Miners Mountain area includes about 85 square miles in Wayne County, south-central Utah. The area is semiarid and characterized by cliffs and deep canyons. Formations range in age from Permian to Upper Jurassic and have an aggregate thickness of about 3,500 feet. Permian formations are the buff Coconino sandstone and the overlying white, limy, shert-containing Kaibab limestone. Unconformably overlying the Kaihab is the lower Triassic Moenkopi formation of reddish-brown and yellow mudstone, siltstone, and sandstone; it contains the Sinbad limestone member (?) in the lower part. Thin, lenticular Shinarump conglomerate unconformably overlies the Moenkopi, but grades upward into the Upper Triassic Chinle formation of variegated mudstone with some interbedded sandstone and limestone lenses. Uncomformably overlying the Chinle are the Wingate sandstone, Kayenta formation, and Navajo sandstone of the Jurassic (?) Glen Canyon group, which consist of red to white sandstone. Only the lower part of the Carmel formation of the Upper Jurassic San Rafael group is exposed in the area; it consists of variegated siltstone, sandstone, limestone, and gypsum. The conspicuous structural feature in the area is the Teasdale anticline which trends northwest, is about 14 miles long, and is asymmetric with a steeper west flank. Bounding the anticline on the northeast and east is the Capitol Reef monocline, the northern part of the Waterpocket Fold. Strata in the area are broken by steeply-dipping normal faults with small displacements, except for the Teasdale fault which has a maximum displacement of over 1,000 feet. Jointing is prominent in some formations. The major orogenic movement in the area is believed to be late Upper Cretaceous to early Tertiary. Epeirogenic uplift occurred intermittently throughout Tertiary and perhaps Quaternary time.

Open-File Report↗