Papers by Wendell Duffield
Grand Falls, AZ, is the site of a massive basalt pour-over that filled the canyon of the Little C... more Grand Falls, AZ, is the site of a massive basalt pour-over that filled the canyon of the Little Colorado River (LCR) in late Pleistocene time. No consensus exists as to which of several nearby cones is the specific source vent, but basalt lava clearly flowed at least 10 km eastward from its ...
The Taylor Creek Rhyolite consists of lava domes and flows that are part of the middle Tertiary M... more The Taylor Creek Rhyolite consists of lava domes and flows that are part of the middle Tertiary MogollonDatil volcanic field in southwestern New Mexico. This rhyolite was emplaced during at least 20 eruptions from as many vents distributed throughout an area of several hundred square kilometers. Each eruption appears to have gone through a unidirectional sequence, beginning with the formation of pyroclastic deposits and ending with the relatively quiet effusion of magma to form a lava dome or flow. Pyroclastic and lava deposits are about equally voluminous, and together they account for about 100 km3 of erupted magma. The volume of individual domes ranges from somewhat less than 1 km3 to about 10 km3. High-precision 40 Ar j39 Ar ages on sanidine phenocrysts, supplemented by the reconstructed length of the path of magnetic secular variation recorded in the lava domes and flows, suggest that the entire Taylor Creek Rhyolite lava field grew in a few thousand years or less. All eruption...
Journal of Volcanology and Geothermal Research, 2007
Gradients in the products of voluminous (102–103 km3) silicic eruptions are widely attributed to ... more Gradients in the products of voluminous (102–103 km3) silicic eruptions are widely attributed to magmatic stratification developed by in situ differentiation over long periods of time (104–105 years) in sub-volcanic chambers. Although the pattern of chemical and mineralogical variations may support magmatic zonation in the source reservoir at the time of eruption, evidence for protracted chamber differentiation is often equivocal. We report trace-element concentrations of sanidine phenocrysts measured by inductively coupled plasma mass spectrometry in the rapidly effused lavas of the 100 km3 Taylor Creek Rhyolite, New Mexico, which link much of the eruptive heterogeneity of the domes and flows to mixing of fresh, crystal-poor, incompatible-element-rich, low-87Sr/86Sr magma from below with partially crystallized, roof-rock contaminated, compatible-element-rich, high-87Sr/86Sr magma resident in the shallow crust. Time constraints provided by high-resolution 40Ar/39Ar geochronology, reconstruction of the path of geomagnetic secular variation, and calculated cooling histories of overlapping eruptive units suggest that inputs from both above and below modified magma compositions during the lifespan of the dome field over periods as brief as a few hundred years or less. These domes thereby provide evidence that chemical gradients need not exist for protracted periods of time prior to eruption of zoned silica-rich magma. Comparisons with some ignimbrites reinforce this view and highlight the importance of processes occurring both at and below the pre-eruptive storage chamber in production of the chemical zonation in silicic systems.
Open-File Report
Total flow from the area. 20omaatic water aupply for private realdanc«. 'irrigation water aupply.... more Total flow from the area. 20omaatic water aupply for private realdanc«. 'irrigation water aupply. *Arteelan flow to aupply water to llvcatock. sDomaatle aupply for Hot Spring* Motel. 6Vind-powared pump. 7The alllec taotharmomater of Fournler and Row* (1966). *the Na-K-Ca gaothermomater of Fourelcr and Truaadall (1973). *m»lag model 1 of Fournlar and Troaadell (1974s). 10MixiBg modal 2 of Fournler and Truaadall (1974t>).
Choice Reviews Online, 2003
American Mineralogist, 1996
The Taylor Creek Rhyolite, a group of coeval, mid-Tertiary, silica-rich rhyolite lava domes in so... more The Taylor Creek Rhyolite, a group of coeval, mid-Tertiary, silica-rich rhyolite lava domes in southwestern New Mexico, is notable for recording bulk-rock evidence of minor, yet easily measurable, contamination of its source magma reservoir resulting from assimilation of Proterozoic roof rock. Most of the evidence is recorded in trace element concentrations and 87Sr/86Sri ratios, which are far different in uncontaminated magma and roof rocks. Hornblende phenocrysts and biotite xenocrysts also record the effects of contamination. Electron microprobe analyses show that all hornblende grains are zoned to Mgrich and Fe-and Mn-poor rims. Rim MgO content is typically about 10 wt% greater than core MgO content. Other hornblende constituents are not measurably variable. Biotite xenocrysts, trace mineral constituents, are present only in the domes that are most contaminated, as judged by bulk-rock variations in trace element concentrations and 87Srl 86Sri. Biotite grains are invariably partly to almost completely altered. Microprobe analyses of the cores of the least-altered grains show that large variations in Fe and Mg and that biotite contains 2-20 times as much Mg as fresh biotite phenocrysts in other silica-rich rhyolite lavas. Fe and Mg are negatively correlated in hornblende and biotite, consistent with mixing two end-member compositions. The mass ratio of contaminant to magma was probably less than 1:100, and major constituents, including AI, were not measurably affected in hornblende. Al-in-hornblende barometry yields essentially a constant calculated pressure of about 1.5 kbar, which is consistent with the interpretation that all contamination occurred in a boundary zone about 300 m thick at the top of the magma reservoir.
Journal of Volcanology and Geothermal Research, 1979
The origin of reverse grading in air-fail pyroclastic deposits has been ascribed to: (1) changing... more The origin of reverse grading in air-fail pyroclastic deposits has been ascribed to: (1) changing conditions at an erupting vent; (2) deposition in water; or (3) rolling of large clasts over smaller clasts on the surface of a steep slope. Structural features in a deposit of air-fall pumice lapilli in the Coso Range, California, indicate that reverse grading there formed by a fourth mechanism during flow of pumice. Reverse-graded beds in this deposit occur where pumice lapilli fell on slopes at or near the angle of repose and formed as parts of the blanket of accumulating pumice became unstable and flowed downslope. The process of size sorting during such flow is probably analogous to that which sorts sand grains in a reverse fashion during avalanching on the slip faces of sand dunes, attributed by Bagnold (1954a) to a grain-dispersive pressure acting on particles subjected to a shear stress. In view of the several ways in which air-fall pyroclastic debris may become reverse graded, caution is advised in interpretation of the origin of this structure both in modern and in ancient deposits.
Journal of Volcanology and Geothermal Research, 1984
The (pre-1982) 850-m-high andesitic stratovolcano E1 Chich6n, active during Pleistocene and Holoc... more The (pre-1982) 850-m-high andesitic stratovolcano E1 Chich6n, active during Pleistocene and Holocene time, is located in rugged, densely forested terrain in northcentral Chiapas, M~xico. The nearest neighboring Holocene volcanoes are 275 km and 200 km to the southeast and northwest, respectively. E1 ChichAn is built on Tertiary siltstone and sandstone, underlain by Cretaceous dolomitic limestone; a 4-km-deep bore hole near the east base of the volcano penetrated this limestone and continued 770 m into a sequence of Jurassic or Cretaceous evaporitic anhydrite and halite. The basement rocks are folded into generally northwest-trending anticlines and synclines. E1 Chich6n is built over a small dome-like structure superposed on a syncline, and this structure may reflect cumulative deformation related to growth of a crustal magma reservoir beneath the volcano. The cone of E1 ChichSn consists almost entirely of pyroclastic rocks. The pre-1982 cone is marked by a 1200-m-diameter (explosion?) crater on the southwest flank and a 1600-m-diameter crater apparently of similar origin at the summit, a lava dome partly fills each crater. The timing of cone and dome growth is poorly known. Field evidence indicates that the flank dome is older than the summit dome, and K-Ar ages from samples high on the cone suggest that the flank dome is older than about 276,000 years. At least three pyroclastic eruptions have occurred during the past 1250 radiocarbon years. Nearly all of the pyroclastic and dome rocks are moderately to highly porphyritic andesite, with plagioclase, hornblende and clinopyroxene the most common phenocrysts. Geologists who mapped El Chich6n in 1980 and 1981 warned that the volcano posed a substantial hazard to the surrounding region. This warning was proven to be prophetic by violent eruptions that occurred in March and April of 1982. These eruptions blasted away nearly all of the summit dome, blanketed the surrounding region with tephra, and sent pyroclastic flows down radial drainages on the flanks of the cone; about 0.3 km 3 of material (density of all products normalized to 2.6 g cm-3) was erupted. More debris entered the stratosphere than from any other volcanic eruption within at least the past two decades. Halite and a calcium sulfate mineral (anhydrite?) recovered from the stratospheric cloud, and anhydrite as a common accessory mineral in 1982 juvenile erupted products may reflect contamination of E1 Chich6n magma by the evaporite sequence revealed by drilling.
Bulletin Volcanologique, 1972
Since February 1969 Alae Crater, a 165-m-deep pit crater on the east rift of Kilauea Volcano, has... more Since February 1969 Alae Crater, a 165-m-deep pit crater on the east rift of Kilauea Volcano, has been completely filled with about 18 million m ~ of lava. The filling was episodic and complex. It involved 13 major periods of addition of lava to the crater, including spectacular lava falls as high as 100 m, and three major periods of draining of lava from the crater. Alae was nearly
ABSTRACT The Alid volcanic center, Eritrea, is a structural dome formed by subvolcanic intrusion ... more ABSTRACT The Alid volcanic center, Eritrea, is a structural dome formed by subvolcanic intrusion of pyroxene-bearing rhyolite, subsequently erupted as pumice and lava, during the period 40,000 to 15,000 years ago. The northern Danakil Depression is thought to be the most recently developed part of the Afar, and represents an active continental rift subparallel to the Red Sea spreading center. The location of Alid may be controlled by the intersection of the structural grain of the NE trending Senafe-Alid lineament with the NW trending Danakil Depression. Our work began as a geothermal assessment (Duffield et al., 1997, USGS Open-file 97-291) that found evidence for 300 meters of vertical offset of early Pleistocene basalt flows over the past 1.1 million years. Structural uplift at Alid reveals Proterozoic metamorphic basement rocks overlain by Quaternary marine sediments including siltstone, and sandstones interbedded with pillow lavas and hyaloclastites. These units are overlain by subaerial amphibole-bearing rhyolites (dated at ~200 ka), basalts, and andesites that were deposited on a relatively flat surface and before significant growth of a large volcanic edifice. About 1 km of structural uplift of the marine sediments began 40 ka when pyroxene-bearing rhyolitic magma intruded close to the surface. Uplift was accompanied by contemporaneous eruptions of pumice falls and more common obsidian domes and lava flows over the next 20,000 years. Uplift apparently ceased after eruption of pyroclastic flows and vent-clogging lava about 15 ka. The pumice deposits contain cognate xenoliths of granophyric pyroxene-granite (Lowenstern et al., 1997, J. Petrol. 38:1707). Our geochronology of the uplift is consistent with the idea that growth of the Alid volcanic center played a role in isolating the southern Danakil Depression from the Red Sea, helping to initiate dessication of the rift and producing the young evaporites found today at Baddha and further south at Dallol. U-Th disequilibrium dating of zircons (SIMS) and mineral separates (TIMS) implies that pyroxene-bearing rhyolitic magma was generated over no more than 50,000 years, most likely by direct fractionation from mafic liquids with incorporation of no more than 5% old crust. Nearly all crystals in the granite xenoliths were formed 250°C (Lowenstern et al., 1998, Geothermics 28: 161). Stable isotopes are consistent with either local recharge or a fossil seawater reservoir. Non-thermal springs are absent, even on the graben floor, but are shown on early 20th century maps by Italian expeditions to the area. The geology and location of Alid, within the Danakil Depression and convenient to the port city of Massawa, suggest that it remains a promising source of geothermal electricity generation in this small, energy-starved nation.
Professional Paper, 1975
The Koae fault system forms part of a continuous fault zone boundary that separates the south fla... more The Koae fault system forms part of a continuous fault zone boundary that separates the south flank from the rest of Kilauea Volcano; the east and southwest rift zones form the rest of the boundary. The Koae system is about 12 km long by 2 km wide and is characterized by gaping cracks and long, sinuous normal fault zones with north-facing scarps. Most fractures are 200 m long or shorter and generally are arranged en echelon. With few exceptions, fractures dip vertically, strike N. 75° E., and have been dilated in a N. 15° W.-S. 15° E. direction. Average dilation across the entire fault system is about 25 m and generally increases eastward along the Koae. Both the trend of the Koae and the direction of dilation virtually parallel those of the lower east rift zone. Recent geodetic studies by D. A. Swanson, W. A. Duffield, and R. S. Fiske (unpub. data, 1973) indicate that the dilation results from the S. 15° E. displacement of the south flank, which in turn is caused by the forceful injection of dikes into the rifts-mostly the east rift. Thus the Koae is believed to represent a tear-away zone as the south flank is pushed southward by dike injection into the rifts. This process has almost certainly been active throughout the history of the Koae and probably will continue as long as Kilauea remains an active volcano.
Open-File Report
Qal Alluvium along streams (Holocene)-Mainly in active flood plains of major and some minor strea... more Qal Alluvium along streams (Holocene)-Mainly in active flood plains of major and some minor streams. Locally, includes outwash related to older phases of the Alaska glaciations. Chiefly stratified boulders, cobbles, gravel, and sand; silt locally common. Qaf Alluvium in fans (Holocene)-Mainly large active fans and cones on steep to gentle slopes adjacent to the broad glaciated valley of the Copper River. Chiefly poorly stratified boulders, cobbles, gravel, and sand. COLLUVIAL DEPOSITS Qc Colluvium, undifferentiated (Holocene and Pleistocene)-Chiefly talus but also includes deposits of small landslides, rock glaciers, and other mass-wasting processes; in places includes large proportion of alluvium in small fans and cones and locally includes remnants of morainal deposits. Chiefly unsorted boulders, cobbles, gravel, and sand. GLACIAL DEPOSITS Qrg Rock glacier deposits (Holocene and Pleistocene)-Deposits in both active rock glaciers, which have well-defined lobate forms, and inactive rock glaciers, which have smooth forms. Chiefly angular blocks and diamicton. Qag Drift of Alaskan glaciation (Holocene)-End, lateral, and ground moraine of the Alaskan glaciations which were deposited during the recession of existing glaciers. In the extensive areas of glacial drift west of Copper Glacier three stages of Alaskan glaciation are recognized (H. Schmoll, written comm., 1994). The youngest stage includes ground, lateral, and end moraines that have been deposited near the margins of present-day glaciers. The two older stages, related to an older phase of Alaskan glaciation and marked by prominent and well-defined lateral moraines, occur further beyond the present-day glacier margins. Dashed line with hachures indicates extent of youngest stage of Alaskan glaciation and locally includes areas within which glaciers have been advancing and retreating during the late 20th century. Plain dashed line separates the two older stages of Alaskan glaciation. Drift is locally modified by colluvial processes, especially along steep eastside of the large nunatak west of Copper Glacier. Diamicton and rubble; local gravel and sand. Qwg Drift of Wisconsin glaciation (Pleistocene)-Chiefly lateral and ground moraine of both younger and older stages of Wisconsin glaciation. Diamicton and rubble; local gravel and sand. Qog Drift of older glaciations (Pleistocene)-Glacial and fluvioglacial deposits observed only in the north wall of the Jacksina Glacier valley where unit is overlain by an agglutinate flow (unit Qaa) that may be as old as 1.38 Ma (Richter and Smith, 1976). Chiefly diamicton; local sand, gravel and boulders. VOLCANIC ROCKS Wrangell volcano-Mount Wrangell (el. 14,163 ft [4317 m]) is a large shield volcano, whose summit area lies mostly to the southwest in tMe contiguous Gulkana A-l and Valdez D-l quadrangles. Only a part of the northeast flank of the shield is exposed in the quadrangle. A porphyritic high-silica andesite lava, similar to that found elsewhere on the Wrangell shield (Richter and others, 1994) is the predominant rock type in the quadrangle.
Professional Paper
The 1969-71 Mauna Ulu eruption on the upper east rift zone of Kilauea Volcano lasted from May 24,... more The 1969-71 Mauna Ulu eruption on the upper east rift zone of Kilauea Volcano lasted from May 24, 1969 to October 15, 1971; it was the longest and most voluminous flank eruption at Kilauea during historic time. About 185 X 106 m3 of basaltic lava was erupted; the lava covered an area of approximately 50 km2 and built a parasitic shield 80 m high. The eruption can be divided into four stages, each of which was dominated by a particular pattern of behavior. The first stage, May 24 to December 30,1969, was characterized by episodes of high or sustained fountaining, each lasting from a few hours to about 3 days and interspersed with longer periods of weak activity. Most fountaining during this stage occurred in one general vent area located 600 m south-southeast of Puu Huluhulu, midway between two large pit craters (since filled), Aloi and Alae Craters. Fountains reached or exceeded 300 m in height during six of the episodes, once towering to a maximum of 540 m. The fountains supplied lava to fast-moving voluminous flows that travelled as far as the coastline, 12 km from the vent. The flows ultimately filled Alae Crater and partly filled Aloi Crater. The periods of weak activity between episodes of strong fountaining lasted from a few days to several weeks, during which time lava splashed and circulated in the vent, sometimes forming low fountains, sometimes quietly upwelling and overflowing the vent. Cyclic rise and fall of the lava column characterized the periods of weak activity. This phenomenon, termed gas-piston activity, is apparently caused by the expansion and subsequent vigorous loss of gas from the column as the gas neared the surface. The second stage, December 31,1969 to July 5,1970, was marked by weak activity at the vent similar to that which characterized the periods between major fountains of the first stage. Lava from a new fissure that opened across Aloi Crater in April completed filling the crater. During this stage, particularly in late May and June, overflows of short duration from the main vent area built a shield, eventually 80 m high; it was at this time that Mauna Ulu ("growing mountain" in Hawaiian) received its name. Much of the activity during this stage was characterized by gas-piston cycles. The third stage, July 6, 1970 to June 14, 1971, was marked by cessation of overflows from the main vent area and the opening of several vents along a new fissure on the east flank of the Mauna Ulu shield. Activity at the new vents was often dominated by gaspiston behavior, and overflows were common. The walls of the fissure at the summit of Mauna Ulu after progressively collapsing formed an ovoid crater within which an active lava lake circulated. Underground conduits from this lake probably supplied lava to the vents on the east flank of Mauna Ulu. Tubes carried lava from these vents into the crusted lava lake occupying Alae Crater, and .07 Peck, Wright, and Moore(1966). 3.3 Moore and Koyanagi (1969).
Geological Survey Professional Paper, 1984
Journal of Geophysical Research, 1980
Thirty-eight separate domes and flows of phenocryst-poor, high-silica rhyolite of similar major e... more Thirty-eight separate domes and flows of phenocryst-poor, high-silica rhyolite of similar major element chemical composition were erupted over the past I m.y. from vents arranged in a crudely S-shaped array atop a granitic horst in the Coso Range, California. Most of the extrusions are probably less than about 0.3 m.y. old. The area is one of Quaternary basaltic volcanism and crustal extension. The central part of the rhyolite field is characterized by high heat flow, low apparent resistivity, and substantial fumarolic activity indicative of an active geothermal system. The immediate source of heat for the surfieial geothermal phenomena is probably a silicic magma reservoir that may still contain molten or partially molten material at a depth of at least 8 km beneath the central part of the rhyolite field. Outlying rhyolite extrusions probably reflect the presence of feeder dikes emanating from the reservoir beneath the central region. Azimuths of dikes appear to be parallel to the regional tectonic axis of maximum horizontal compression, analogous to some dike-fed flank eruptions on basaltic shields and andesitic stratovolcanoes. The areal extent of a magma reservoir and the present total heat content of the silicic magma system at Coso may be less than was previously estimated. However, the area is still considered to be one of significant geothermal potential.
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Papers by Wendell Duffield