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Volcanic Rocks of the Mimbres and Upper Gila Drainages, New Mexico Wolfgang E

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Volcanic Rocks of the Mimbres and Upper Gila Drainages, New Mexico Wolfgang E New Mexico Geological Society Downloaded from: http://nmgs.nmt.edu/publications/guidebooks/16 Volcanic rocks of the Mimbres and upper Gila drainages, New Mexico Wolfgang E. Elston, 1965, pp. 167-174 in: Southwestern New Mexico II, Fitzsimmons, J. P.; Balk, C. L.; [eds.], New Mexico Geological Society 16th Annual Fall Field Conference Guidebook, 244 p. This is one of many related papers that were included in the 1965 NMGS Fall Field Conference Guidebook. Annual NMGS Fall Field Conference Guidebooks Every fall since 1950, the New Mexico Geological Society (NMGS) has held an annual Fall Field Conference that explores some region of New Mexico (or surrounding states). Always well attended, these conferences provide a guidebook to participants. Besides detailed road logs, the guidebooks contain many well written, edited, and peer-reviewed geoscience papers. These books have set the national standard for geologic guidebooks and are an essential geologic reference for anyone working in or around New Mexico. Free Downloads NMGS has decided to make peer-reviewed papers from our Fall Field Conference guidebooks available for free download. Non-members will have access to guidebook papers two years after publication. Members have access to all papers. This is in keeping with our mission of promoting interest, research, and cooperation regarding geology in New Mexico. However, guidebook sales represent a significant proportion of our operating budget. Therefore, only research papers are available for download. Road logs, mini-papers, maps, stratigraphic charts, and other selected content are available only in the printed guidebooks. Copyright Information Publications of the New Mexico Geological Society, printed and electronic, are protected by the copyright laws of the United States. No material from the NMGS website, or printed and electronic publications, may be reprinted or redistributed without NMGS permission. Contact us for permission to reprint portions of any of our publications. One printed copy of any materials from the NMGS website or our print and electronic publications may be made for individual use without our permission. Teachers and students may make unlimited copies for educational use. Any other use of these materials requires explicit permission. This page is intentionally left blank to maintain order of facing pages. 167 VOLCANIC ROCKS OF THE MIMBRES AND UPPER GILA DRAINAGES, NEW MEXICO WOLFGANG E. ELSTON The University of New Mexico, Albuquerque, New Mexico INTRODUCTION the volcanics once again form a continuous plateau, one of the largest, but least known, magmatic prov- The Sixteenth Field Conference carries the New inces of our planet. Mexico Geological Society through parts of one of The tectonic setting of the volcanic province is the world's greatest volcanic provinces. There is rarely worth noting. Part of it coincides with parts of the a moment when volcanic rocks, mainly of Tertiary age, Mexican geosyncline but it spreads far beyond the are not visible. Andesite, latite, and rhyolite predom- limits of any geosyncline, across the Basin and Range inate; basalt is relatively scarce. Province and into the Colorado Plateau. Many geolo- The dominant influence of volcanics on the ge- gists have assumed that geosynclinal belts and vol- ology of southwestern New Mexico was apparent as canism of the andesite-rhyolite family are inextricably early as 1905 when the great Waldemar Lindgren de- linked. From this, astronomers and geophysicists have voted a lengthy section of his classic report (in Lind- concluded that bodies like the Moon or Mars that gren, Graton, and Gordon, 1910) to their distribution, lack geosynclines must also lack large scale non-basaltic stratigraphy, and petrography. In the succeeding 60 volcanism. Detailed study of the Cordilleran orogenic years many local details have been worked out, mainly belt suggests that this notion is a gross oversimplifica- by geologists of the U.S. Geological Survey and the tion. New Mexico Bureau of Mines and Mineral Resources, The material in this article that refers to rocks of but many fundamental question remain unanswered. the Upper Gila drainage basin has not been published How and where was the magma generated and differ- previously. Except where specifically credited to other entiated, 104 to 105 cubic kilometers of which was sources, it was gathered during 1964-65, in the course ejected in southwestern New Mexico alone? What of a project that is still far from finished. It must be was the mechanism of eruption? Where were the regarded as tentative. Figure 1 shows localities men- eruptive centers, and what structures controlled them? tioned in the text. What were the tectonic effects of the withdrawal of this vast volume of magma from its reservoirs? What relationship, if any, do the oldest eruptive centers have VOLCANIC SUCCESSION to the metal-bearing porphyry bodies? Finally, what Superficially seen, the stratigraphic succession seems was the source of energy for volcanism on so immense simple: in many places andesite is overlain by rhyolite, a scale? Our principle of uniformitarianism is put to which in turn, is overlain by basalt. This simplicity is a severe test. Nowhere have eruptions of this magni- deceptive. As field work progresses, it is becoming tude been recorded in historic time. This becomes apparent that rocks which look alike are not necessar- especially apparent when we consider the volumes of ily of the same age. Conversely, unlike rocks from individual rhyolite ash-flow cooling units such as the different eruptive centers are found to interfinger Kneeling Nun Rhyolite (see article by D. L. Giles, (fig. 2). Specifically, the andesite-rhyolite association this guidebook) . (which includes rock like latite, intermediate between Impressive as it is, the volcanic province of south- andesite and rhyolite) recurs many times. The dark western New Mexico is only a small block of the basaltic-looking rocks do indeed occur late in the circum-Pacific belt. More locally, the relatively con- history of the region, but detailed studies show them tinuous volcanic rocks of the Mogollon Plateau north to include many petrographic types, from rocks on the of Silver City continue to the south and southwest, rhyolite-latite boundary to, rarely, true olivine-bearing where their former continuity has been broken by basalts. Basin and Range faults. Similarities in volcanic sec- tions of adjacent ranges indicate that they were once CRETACEOUS AND EARLY TERTIARY VOLCANIC ROCKS parts of a nearly continuous blanket thousands of feet Field evidence has indicated late Cretaceous or very thick, consisting of many local lenticular units. Farther early Tertiary age for the oldest, dominantly andesitic, south yet, in the Sierra Madre Occidental of Mexico, volcanic rocks. Between Silver City and Pinos Altos, 1. Research supported by NASA grant NGR-32-004-011. for instance, andesite breccias have been intruded by Reserve .SOCORRO PELONA cr BEARWAL Low, CA TRONen.,-.. m°93r 11:1 froslor Well Cr.* ., 0 c Loki. I Glenwood e • n GILA CLIFF DWELLINCS 5NI/C0i NATIONAL MONUMENT SIERRA 0, PEEDS? 48 PEAK.s,, /0 Mule Cr 11 Z ,se. 0?-( Cliff .": G R A N T RoMboro MicArs N., X Steeple Rock SCN LHO $.` Veden Lake Volley • •Macho 0 Z CAN ADO M PEAK – _ * NJ 3 o 3 Numbers show locations Z )o. X of restored columnar sections 0 in Figure 2. 0 5 10 15 20 SCALE IN MILES ..: StWAS Deming ....::. > I C,, U A I ...;,, .? ! DONA ,.., I AN A L 1 oHochito 0,, , y *' ,.. ““, –4--,-;- — PR :Et ,,. HILLS 1 - - - NEW MEXICO- ___ _ 1 0 1 REPUBLIC OF MEXICO C H D A L GO /s. S E, .-.`:-. rr. s :1 O ,. k i 0 rk t.k ,..; ;,. N • ,t L ..■ .. ■ .. ., .. j FIGURE 1 Map of Southwestern New Mexico, showing localities mentioned in the text. POST-BASALT ROCKS 0 Latite 9ass/1 _________________ Basalt Sandstone,. ___ Rhyolite tuff Mogollon Andesite Dog Gulch Formation Bear Springs Basalt _ _____ z adwood Gulch Rh Mogollon Andesite Andesite loon- RannsiontJiff _ Ji Basalt BASALTIC Basaltic andesite GROUP Razorback rhyolite member Latite Moonstone Tut Deadwood Gulch Rhyolite Tuff Sandstone Fonney Rhyolite Razorback andesite membe Moonstone Tuff Quartz latite ash-flow tuff Last Chance Andesite Cabello Blanco Rhyoid Rhyolite flows Rustler Canyon Basolt\ xtt Rhyolite flows Box Canyon Rhyolite Fonney Rhyolite Moonstone Tuff Mimbres Peak Formation 0 t2tol ash-flow tuffs Rhyolite and quartz latite cute ang Nide Simard Creek Andesite ash-flow tuff Kneeling Nun Rhyolite nt, Pacific Quartz Latite 0 Cranktown Sandstone Sugarlump Rhyolite Tuff U 0 Basement Houston Andesite nnlaog C) Cooney Quartz Latite DATIL EXPLANATION oouno GROUP 54= C/) 1:11:111112 Whitewater Creek Rhyolite C) SUPERIMPOSED SYMBOLS 44 Parts of intrusive-extrusive 1-----1 complexe Basalt RhyoliN and Moonstone Tuff Rubio Peak Formation quartz afire tuffs (exclusive of ash-flow tuffs) Botite-rich two feldspar rhyNites Approximate Basaltic and quartz lotites soonVertical Scale, C/) adesite, SIMMS in feet ondesite one (ante Rhyolite and Whitewater Creek Rhyolite- 0001 quartz Htite Cooney Quartz Latite section ash-flaw tuffs t=ltt Rhyolite and z Basement quart: Wife flows Conglarnerote, sandstone, and tuffoceous sandstone tot Pre-Dotil rocks FIGURE 2 zo Tentative correlation of Tertiary volcanic rocks of parts of the Mimbres and upper Gila drainages. Locations of restored columnar sections and sources of data: 1) Dwyer quadrangle (Elston, 1957); 2) State Highway 61, between Rocky Canyon and Black Canyon (Elston, this article); 3) Pinos Altos Range between
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