Tectonics of southeastern Arizona

Drewes, Harald

doi:10.3133/pp1144

Cited by 38 publications

(29 citation statements)

References 18 publications

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“…Range-wide geologic-map coverage has also been completed, essentially by two generations of workers (Sabins, 1957a;Cooper, 1960;Erickson, 1968;Drewes, 1984Drewes, , 1985Drewes, , 1986andErickson andDrewes, 1984a and1984b). Regional maps and reports bearing on the study area are also available (Gilluly, 1956;Drewes, 1980Drewes, , 1981and Drewes and others, 1985). A summary description of some mines is given by Richter and Lawrence (1983) and by others they cite.…”

Section: Investigations By the Us Geological Surveymentioning

confidence: 99%

Mineral resources of the Dos Cabezas Mountains Wilderness Study Area, Cochise County, Arizona

Drewes¹,

Abrams²,

Hassemer³

et al. 1986

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LOW mineral resource potential is assigned to areas where geologic, geochemical, and geophysical characteristics define a geologic environment in which the existence of resources is unlikely. This broad category embraces areas with dispersed but insignificantly mineralized rock as well as areas with few or no indications of having been mineralized. MODERATE mineral resource potential is assigned to areas where geologic, geochemical, and geophysical characteristics indicate a geologic environment favorable for resource occurrence, where interpretations of data indicate a reasonable likelihood of resource accumulation, and (or) where an application of mineral-deposit models indicates favorable ground for the specified type(s) of deposits. HIGH mineral resource potential is assigned to areas where geologic, geochemical, and geophysical characteristics indicate a geologic environment favorable for resource occurrence, where interpretations of data indicate a high degree of likelihood for resource accumulation, where data support mineral-deposit models indicating presence of resources, and where evidence indicates that mineral concentration has taken place. Assignment of high resource potential to an area requires some positive knowledge that mineral-forming processes have been active in at least part of the area. UNKNOWN mineral resource potential is assigned to areas where information is inadequate to assign low, moderate, or high levels of resource potential. NO mineral resource potential is a category reserved for a specific type of resource in a well-defined area. Abstracted with minor modifications from: The USGS (U.S. Geological Survey) and the USBM (U.S. Bureau of Mines) studied 11,921 acres of the Dos Cabezas Mountains Wilderness Study Area (AZ-040-065) in Cochise County, Arizona. The study of this acreage was requested by the BLM (U.S. Bureau of Land Management). In this report, the studied area is called "wilderness study area" or just "study area." The wilderness study area covers about 18.6 sq mi (square miles) of the northeast flank of the Dos Cabezas Mountains in southeastern Arizona, where they lie just south of Interstate Highway 10 and 3-18 mi east and southeast of Willcox. Geologic, geochemical, geophysical, and mine and prospect studies were undertaken by the USGS and the USBM mainly during 1984. These followed more extensive geologic studies of the entire range, as well as studies of adjacent ranges. As a result of these investigations, about 3 sq mi of the study area is assigned a moderate mineral resource potential for porphyry, skarn, stockwork, massive-sulfide replacement, and vein deposits of copper, lead, zinc, molybdenum, tungsten, and silver. (In this report the term "deposit" does not carry a connotation of economic value.) Additionally, an identified resource of a silver-and gold-bearing quartz vein suitable for smelter flux is present. The rest of the area is assigned a low resource potential for both metallic and nonmetallic deposits. Levels of Certainty

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Section: Investigations By the Us Geological Surveymentioning

confidence: 99%

Mineral resources of the Dos Cabezas Mountains Wilderness Study Area, Cochise County, Arizona

Drewes¹,

Abrams²,

Hassemer³

et al. 1986

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“…The Paleozoic sequences in southern Arizona are composed mainly of Cambrian strata overlain disconformably by a Devonian-Permian sequence of limestone, dolomite, and interbedded mudstone to sandstone (Butler, 1971), suggesting marine conditions transitioned to sub aerial (Drewes, 1981) during the Devonian to Permian.…”

Section: Geologic and Tectonic Historymentioning

confidence: 99%

“…After Dickinson, 1989. batholiths were emplaced ( Figure 1.2-B) (Davis, 1981;Drewes, 1980). A rifting event characterized by high angle faulting and diabase dike, sill and sheet intrusions occurred in the Late Proterozoic (1.1 Ga) (Davis, 1981;Dickinson, 1989;Drewes, 1981;Howard, 1991). In the period 1.1-0.6 Ga, episodic rifting oriented N23ºW…”

Section: Geologic and Tectonic Historymentioning

confidence: 99%

“…Ma) (Dickinson, 1989) Synorogenic high angle block faulting (Figure 1.3, shortening N71ºE, Davis, 1981) with differential uplift caused mass-wasting and removal of all or parts of the Paleozoic section throughout Arizona (Davis, 1981;Drewes, 1981) while newly created basins filled with volcanic and sedimentary rocks (Drewes, 1981) defines the northern extent of the known great thickness of Jurassic plutonic rocks in Arizona (Titley, 1976). This fault zone is thought to have been active at various times throughout the Mesozoic (Titley, 1982).…”

Section: Geologic and Tectonic Historymentioning

confidence: 99%

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Structure of the Tucson Basin, Arizona from gravity and aeromagnetic data

Rystrom¹

2003

Open-File Report

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Interpretation of gravity and high-resolution aeromagnetic data reveal the three-dimensional geometry of the Tuscson Basin, Arizona and the lithology of its basement. Limited drill hole and seismic data indicate that the maximum depth to the crystalline basement is approximately 3600 meters and that the sedimentary sequences in the upper ~2000 m of the basin were deposited during the most recent extensional episode that commenced about 13 Ma. The negative density contrasts between these upper Neogene and Quaternary sedimentary sequences and the adjacent country rock produce a Bouguer residual gravity low, whose steep gradients clearly define the lateral extent of the upper ~2000m of the basin. The aeromagnetic maps show large positive anomalies associated with deeply buried, late Cretaceousearly Tertiary and mid-Tertiary igneous rocks at and below the surface of the basin. These magnetic anomalies provide insight into the older (>13 Ma) and deeper structures of the basin. Simultaneous 2.5-dimensional modeling of both gravity and magnetic anomalies constrained by geologic and seismic data delineates the thickness of the basin and the dips of the buried faults that bound the basin. This geologic-based forward modeling approach to using geophysical data is shown to result in more information about the geologic and tectonic history of the basin as well as more accurate depth to basement determinations than using generalized geophysical inversion techniques. CONTENTS

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“…Most outcrops of the Bfiucarit Formation are located at the westena foothills of the Sierra Madre Occidental province. The maximum observed thickness of this formation does not exceed 400 m. The age of the sediments is constrained as they overlay basalts dated at 17.6 My in the region of Ydcora (Bockoven 1980) and as they underlie volcanic rocks dated around 14 My (Drewes 1981;Bartolini et al 1992). The presence of heulandite, as a cement, within sandstones was pointed out by Cochem6 et al (1988).…”

Section: Geological Settingmentioning

confidence: 99%

Alteration of Silicic Vitric Tuffs Interbedded in Volcaniclastic Deposits of the Southern Basin and Range Province, Mexico: Evidences for Hydrothermal Reactions

Münch¹

1996

Clays and clay miner.

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Abstract--In Northwestern Mexico, the Miocene basins that disrupted the Sierra Madre Occidental Province are filled with sandstones and conglomerates (the B~ucarit Formation) cemented mainly by zeolites of the heulandite-clinoptilolite group. Few volcanic tufts are intercalated in the sediments for which four different groups of samples have been defined. These groups correspond to a gradation in the alteration of the glassy matrix. Group 1 is characterized by the preservation of the glassy matrix and the presence of disseminated patches of clay minerals with a continuous variation between aluminous Al-montmorillonite and ferric smectite end-members. Heulandite-group zeolites and opal C-T are also present. Group 2 is characterized by a nearly complete replacement of volcanic glass by a more homogeneous A1-montmorillonite. In some samples, heulandite-group zeolites are present as clusters on clay minerals. The primary vitroclastic texture is generally preserved and relict glass is present in small amounts. In group 3, the secondary assemblage is dominated by heulandite-group zeolite crystals as pseudomorphs of shards and pumiceous fragments. Discrete illite is present in all samples. Textures are exceptionally well-preserved. Group 4 is characterized by the presence of heulandite and clay minerals in which the Mg-Fe smectite end-member is more magnesian than in other groups. The original texture is not preserved.The following are deduced from the mass-balance calculations: the alteration of the tuffs leads to a strong Mg-and Ca-and, to a lesser degree, Fe-enrichment, and to Na and K depletion. Zeolites account for Ca-enrichment and clay minerals are host for Fe and Mg. As a consequence, alteration may have occurred under open system conditions and the most likely source for the high Ca and Mg gains is a fluid circulating through the underlying volcaniclastic sediments and underlying mid-Tertiary volcanics of the bimodal (basaltic-rhyolitic) sequence. However, those fluids may have been rather dilute and weakly alkaline.As estimated temperatures are between 85 and 125~ and as there is only a low burial, it is proposed that hot fluids are responsible for the alteration of volcanic glass. A decrease with time in the initial permeability of the tuffs is consistent with the observed evolution of the changing Al-smectite toward a more magnesian composition.

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Tectonics of southeastern Arizona

Cited by 38 publications

References 18 publications

Mineral resources of the Dos Cabezas Mountains Wilderness Study Area, Cochise County, Arizona

Mineral resources of the Dos Cabezas Mountains Wilderness Study Area, Cochise County, Arizona

Structure of the Tucson Basin, Arizona from gravity and aeromagnetic data

Alteration of Silicic Vitric Tuffs Interbedded in Volcaniclastic Deposits of the Southern Basin and Range Province, Mexico: Evidences for Hydrothermal Reactions

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