Cone Sheets Research Articles

VOLCANIC STRUCTURES IN THE CHUSKA MOUNTAINS, NAVAJO RESERVATION, ARIZONA–NEW MEXICO

Research Article| April 01, 1957 VOLCANIC STRUCTURES IN THE CHUSKA MOUNTAINS, NAVAJO RESERVATION, ARIZONA–NEW MEXICO CONRAD R APPLEDORN; CONRAD R APPLEDORN DEPARTMENT OF GEOLOGY, UNIVERSITY OF MINNESOTA, MINNEAPOLIS, MINNESOTA Search for other works by this author on: GSW Google Scholar H. E WRIGHT, JR. H. E WRIGHT, JR. DEPARTMENT OF GEOLOGY, UNIVERSITY OF MINNESOTA, MINNEAPOLIS, MINNESOTA Search for other works by this author on: GSW Google Scholar Author and Article Information CONRAD R APPLEDORN DEPARTMENT OF GEOLOGY, UNIVERSITY OF MINNESOTA, MINNEAPOLIS, MINNESOTA H. E WRIGHT, JR. DEPARTMENT OF GEOLOGY, UNIVERSITY OF MINNESOTA, MINNEAPOLIS, MINNESOTA Publisher: Geological Society of America Received: 09 Mar 1956 First Online: 02 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Copyright © 1957, The Geological Society of America, Inc. Copyright is not claimed on any material prepared by U.S. government employees within the scope of their employment. GSA Bulletin (1957) 68 (4): 445–468. https://doi.org/10.1130/0016-7606(1957)68[445:VSITCM]2.0.CO;2 Article history Received: 09 Mar 1956 First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation CONRAD R APPLEDORN, H. E WRIGHT; VOLCANIC STRUCTURES IN THE CHUSKA MOUNTAINS, NAVAJO RESERVATION, ARIZONA–NEW MEXICO. GSA Bulletin 1957;; 68 (4): 445–468. doi: https://doi.org/10.1130/0016-7606(1957)68[445:VSITCM]2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract The Chuska Mountains, in northwestern New Mexico and adjacent Arizona, consist of flat-lying Miocene (?) sedimentary rocks locally overlain by pyroclastic and flow rocks of the Pliocene Navajo-Hopi volcanic province. The volcanic rocks were extruded into deep valleys cut into the top and flanks of the mountains.Five volcanic centers within the Chuska Mountains were examined in detail. (1) The depression of Washington Pass is floored by three lava flows underlain by fluvial deposits of pyroclastic origin and overlain by a rubble dome intruded by plugs and dikes of minette. Minor caldera subsidence is indicated by faults in the Chuska sandstone underlying the volcanic rocks, by folds in the lava and tuff, and by steep inward dips of the volcanic rocks in the rim of the circular depression. (2) The Palisades represent an erosional remnant of a thick valley fill of coalesced domes of lava and agglomerate from several closely spaced vents. The flow rocks overlie fluvial beds of sandy tuff eroded from the slopes and deposited in the valley bottoms. The lava and tuff rest on slopes as high as 60°. (3) East Sonsela Butte is capped by three lava flows deposited in valleys cut into the Pliocene Chuska Mountains, and West Sonsela Butte is a remnant of a low, flat dome of lava and rubble capping a crater filled with coarse explosion breccia. (4) Tsailee Butte is a plug of columnar lava intruding a cone of coarse tuff-breccia, and South Tsailee Butte is a remnant of a fluvial crater filling of interbedded sand and tuff cut by a thick cone sheet of minette. (5) Roof Butte is formed from two funnel-shaped explosion pipes, one of which is capped by a low lava dome.The vents of the Chuska Mountains have similar eruptive and structural histories. The volcanism was explosive in its early stages, and large quantities of pyroclastic material were ejected in numerous phreatic explosions. Between eruptions the craters of the low, flat cones were quickly filled with fluvial deposits of sand and tuff stripped from bordering valley walls. Collapse and inward sliding of the soft fluvial layers in the crater walls are shown by faults, crumpled and sheared layers, and folds. Volcanic activity ended with quiet extrusion of viscous lava and intrusion of dikes and plugs. The volcanic rocks consist of alkalic sanidine trachybasalt and minette. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Ring structures at Mauna Kea, Hawaii

Macdonald briefly discusses the geology of Mauna Kea. The rocks consist of the older Hamakua volcanic series, with a lower member composed largely of primitive basalts and an upper member containing more highly differentiated types, and the younger Laupahoehoe volcanic series composed largely of andesites, with which are interbedded glacial deposits. Besides the radial rift zones, Mauna Kea also shows concentric arcuate alignments of vents, indicating arcuate fractures occupied at depth by ring dikes or cone sheets. The arcuate alignment of vents appears to result from the intersection of shallow-seated radial fissures with the deeper arcuate intrusions.

Volcanic Centers of the Sunlight Area Park County, Wyoming

The Sunlight area is located in the northern Absaroka Mountains of northwestern Wyoming. The rocks are dominantly Tertiary pyroclastics and basalt flows which rest on flat-lying Paleozoic limestones. The pyroclastics were thrown out from a large number of vents in explosive eruptions and were later modified by mud flows. Two major volcanic centers and one small explosive vent have been found in the Sunlight area. Intrusions of stocks, laccoliths, plugs, cone sheets, and radial dike systems are closely related to the volcanic centers. The radial dikes were formed by magma moving horizontally outward from the intrusive centers in vertical cracks. The Sunlight centers are similar in many respects to the Scottish Tertiary volcanoes. The rock types in general show a normal differentiation series from olivine gabbro and basalt through diorite and andesite to sodic syenite and trachyte. Several unusual orthoclase-bearing basalts, known as the absarokite series, are also present.

The ore deposits of the Sunlight mining region, Park County, Wyoming

The Sunlight mining region lies in the Absaroka Mountains, Wyo. The deposits are twenty miles from the nearest road and are not developed. The mineralization is genetically associated with an intrusive and volcanic center made up of a small stock of syenite and diorite, several basaltic plugs, hundreds of radially-arranged dikes, and a few cone sheets, all in the Early Basic Breccia Series of the Absarokas. The deposits are small, irregular fissure veins in fault zones and along dike contacts in the Tertiary Volcanic breccias.The common ore minerals are pyrite, chalcopyrite, galena, and tetrahedrite with pockety values in gold and silver. The gangue is essentially carbonates and quartz. The deposits have the banded and vuggy character of typical epithermal veins; they exhibit a vertical zoning that is well exposed due to the 3,000 foot relief, and seems to have been dependent on a vertical temperature gradient that existed in the roots of the volcano shortly after its activity had ceased. In the deepest zone are pyrite-quartz veins and above them successively, chalcopyrite-pyrite-gold, chalcopyrite, galena, and galena-silver veins in a 2,000 foot range.