Hopi Buttes volcanic field, Hopi Buttes Mining District, Navajo Co., Arizona, USAi
|Regional Level Types|
|Hopi Buttes volcanic field||- not defined -|
|Hopi Buttes Mining District||Mining District|
Hopi Buttes volcanic field is a monogenetic volcanic field located on the Colorado Plateau mostly on the Navajo Reservation around the town of Dilkon in northeastern Arizona north of Holbrook.
The volcanic field covers an area of approximately 965 square miles (2,500 km2) and contains about 300 maars and diatremes.
Most of the volcanic activity occurred between 8.5 and 6 million years ago, with the most recent dated at 4.2 million years ago.
At least 23 vents are exposed within approximately 51 km2 of the First Flat Mesa area in the north-central Hopi Buttes. Locally these vents provide well-preserved exposures of marginal deposits, maar crater deposits, and country rock. These units provide critical geologic constraints regarding the vertical and lateral facies changes that occur proximal to the vent. Ten volcanic facies, three limestone facies, and one marl facies have been described and provide spatial and temporal information about processes and interactions that occur within and adjacent to the vent during a phreatomagmatic eruption. A majority of these facies suggest magma interaction with water-saturated sediment which created explosive eruptions that produced juvenile lapilli, blocks and bombs, and clasts of country rock that were recycled within the vent or dispersed away from the vent by base surges or fallout. These consist of massive lapilli tuff to moderately bedded lapilli tuff that typically contains blocks and bombs up to 2-3 meters. Where vents occur within close proximity, saturated sediments filling one crater may break the wall between them and slump from one vent into the neighboring vent as it is erupting. Some eruptions began phreatomagmatically, used up the available water, and became magmatic, producing scoria deposits that filled in the craters. Crater-lake facies suggest that most of the material removed by the eruption was deposited outside of the crater, allowing water to fill the crater and deposit limestone. Crater-lake facies are not found in vents where scoria deposits are found, although occasionally lapilli and ash are found within the limestone, from a nearby vent eruption and depositing volcanic material into the lake. Facies descriptions and interpretations provided information used to produce an eruptive model for the vents within the study area.
Regions containing this locality
|North America Plate||Tectonic Plate|
|Colorado Plateau, USA||Plateau|
|Navajo Nation Indian Reservation, USA||Reservation|
|Hopi-Navajo Indian Reservations, Colorado Plateau, Apache; Navajo and San Juan Cos., Arizona & Utah, USA|
Select Mineral List TypeStandard Detailed Strunz Dana Chemical Elements
Commodity ListThis is a list of exploitable or exploited mineral commodities recorded at this locality.
1 valid mineral.
Detailed Mineral List:
| ⓘ Analcime|
Formula: Na(AlSi2O6) · H2O
Description: Occurs in mafic volcanic rocks.
Reference: Anthony, J.W., et al (1995), Mineralogy of Arizona, 3rd.ed.: 108; Williams, H. (1936), Pliocene volcanics of the Navajo-Hopi country, Geol. Soc. Am. Bull.: 47: 111-172;Tschernich, R. (1992): Zeolites of the World, 64
List of minerals arranged by Strunz 10th Edition classification
|Group 9 - Silicates|
|ⓘ||Analcime||9.GB.05||Na(AlSi2O6) · H2O|
List of minerals arranged by Dana 8th Edition classification
|Group 77 - TECTOSILICATES Zeolites|
|Zeolite group - True zeolites|
|ⓘ||Analcime||22.214.171.124||Na(AlSi2O6) · H2O|
List of minerals for each chemical element
|H||ⓘ Analcime||Na(AlSi2O6) · H2O|
|O||ⓘ Analcime||Na(AlSi2O6) · H2O|
|Na||ⓘ Analcime||Na(AlSi2O6) · H2O|
|Al||ⓘ Analcime||Na(AlSi2O6) · H2O|
|Si||ⓘ Analcime||Na(AlSi2O6) · H2O|
This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.
Click on geological units on the map for more information. Click here to view full-screen map on Macrostrat.org
0 - 0.0117 Ma
|Mixed alluvium and eolian deposits|
Age: Anthropocene (0 - 0.0117 Ma)
Description: Gray, light-red, and brown clay, silt, and fine- to coarse-grained sand interbedded with lenses of pebbly gravel. Deposits on Newberry and Ives Mesas (sheet 1) contain white, angular to subangular chert fragments locally derived from the Owl Rock Member of the Chinle Formation. Deposits within Hopi Buttes (sheet 2) contain black, white, and gray, angular to subrounded volcanic fragments locally derived from nearby volcanic outcrops. Unit has accumulated by both alluvial and eolian processes, resulting in interbedded sequence of thin-bedded, mixed clay, silt, sand, and small gravel, typical of young fluvial (Qa1, Qa2) and eolian (Qd, Qes) deposits. Subject to sheet-wash erosion during wet conditions and accumulation of eolian-sand deposits during dry conditions. Commonly overlies young fluvial and eolian surficial deposits (Qf, Qf1, Qf2, Qf3, Qa1, Qa2) and often is overlapped by young or fresh eolian-sand deposits (Qd, Qes). Supports light to moderate growths of grass, cactus, and small high-desert shrubs. Thickness, 1 to 6 m (3 to 20 ft)
Reference: Billingsley, G.H., D. Block, and M. Hiza Redsteer. Geologic map of the Winslow 30’ × 60’ quadrangle, Coconino and Navajo Counties, northern Arizona. U.S. Geological Survey Scientific Investigations Map 3247. 
2.588 - 5.333 Ma
|Cenozoic sedimentary rocks|
Age: Pliocene (2.588 - 5.333 Ma)
Lithology: Sedimentary rocks
Reference: Chorlton, L.B. Generalized geology of the world: bedrock domains and major faults in GIS format: a small-scale world geology map with an extended geological attribute database. doi: 10.4095/223767. Geological Survey of Canada, Open File 5529. 
|Zanclean - Tortonian|
3.6 - 11.62 Ma
|Pliocene to late Miocene basaltic rocks|
Age: Neogene (3.6 - 11.62 Ma)
Description: Mostly dark, inconspicuously flat, low-lying or mesa-forming basalt deposited as lava flows. Rocks included in this unit are located almost entirely in the large volcanic fields south and west of Flagstaff, in smaller fields in northwesternmost Arizona, and in the Hopi Buttes volcanic field on the Navajo and Hopi Indian Reservations north of Holbrook. Original volcanic landforms have been obscured by erosion. (4-8 Ma)
Comments: Chiefly Hopi Buttes, "Rim basalts", volcanic fields in northwesternmost Arizona Original map source: Arizona Geological Survey, DI-8 Geologic Map of Arizona, Digital Spatial data for the Geologic Map of Arizona, v. 3.0, edited by S.M. Richard and S.M. Kneale, 2002, 10 p., 2 DOS HD disks. Arc/INFO export file (.e00) format, scale 1:1,000,000.
Reference: Horton, J.D., C.A. San Juan, and D.B. Stoeser. The State Geologic Map Compilation (SGMC) geodatabase of the conterminous United States. doi: 10.3133/ds1052. U.S. Geological Survey Data Series 1052.