Geology and tectonic setting of the Mule Creek caldera, New Mexico, U.S.A (original) (raw)
Related papers
Journal of Geophysical Research, 1991
Volcanic and shallow plutonic (hypabyssal) levels of the Turkey Creek caldera, located in southeast Arizona, are exposed as a consequence of uplift and erosion. The 4øAr/39Ar geochronology and paleomagnetic data indicate that the caldera cycle was relatively short lived and occurred at about 26.9 Ma, coincident with early phases of ductile extension in the southern Basin and Range. The caldera is a transitional calc-alkali to alkalic magmatic system and is similar to other relatively small volcanicplutonic centers that formed after the main pulse of compressional calc-alkalic magmatism in the Cordillera. Trace element ratios and elemental distribution patterns for Turkey Creek rocks are consistent with origin in a transitional subduction to within-plate extensional setting. Field relations also suggest synextensional magmatism; regional northwest trending high-angle faults offset early caldera rocks but are buried by late moat rhyolite. Caldera collapse accompanied eruption of more than 500 km 3 of high-silica rhyolite tuff (the Rhyolite Canyon Tuff). Eruption of the tuff was followed immediately by emplacement of a dacite porphyry intrusion, probably a thick laccolith, into the caldera fill and by extrusion of the dacite porphyry from ring-fracture-hosted feeders. Intracaldera tuff at the roof of the intrusion was metamorphosed and brecciated to produce low-pressure shockmetamorphic effects and was locally melted. Interpretation of the intrusion as an intracaldera laccolith readily explains a lack of floor rocks within the caldera and the absence of intracaldera equivalents of most of the outflow tuff. Intrusion of intracaldera laccoliths may represent a relatively common, though rarely rec,oxgnized process within calderas. Stratigraphic relations, rare mingled rocks, and 40 3v overlapping Ar/ Ar ages indicate that both high-silica rhyolite magma (Rhyolite Canyon Tuff) and dacite porphyry magma were present in the source reservoir (rhyolite above dacite) and were separated by a sharp interface. Dacite porphyry magma from beneath the interface was drawn up into and erupted from vents that previously fed ash flow eruptions; some dacite porphyry was trapped in and beneath the vents and solidified to form a ring dike at depth. Following an erosional hiatus of -<0.3 m.y., rhyolite was again erupted, filling the caldera moat with --•135 km 3 of mainly aphyric high-silica rhyolite. Gradational contacts with underlying densely welded tuff, relatively large volumes, planiform aspect ratios, and superliquidus temperatures suggest that some of the laminated rhyolites are rheomorphic tuff. Eruption of moat rhyolites records generation of a voluminous new batch of mainly high-silica rhyolite with a distinct geochemical signature. The Turkey Creek caldera is a high-silica rhyolite and dacite magmatic system that formed at 26.9 Ma (average 4øAr/39Ar age, see below) during the transition from Laramide and mid-Tertiary compression to Basin and Range extension in southeast Arizona. The caldera and related mid-Tertiary volcanic and plutonic centers of southeastern Arizona and southwestern New Mexico provide a link This paper is not subject to U.S. copyright. Published in 1991 by the American Geophysical Union. Paper number 91JB00067. between the larger and more intact San Juan and Mogollon-Datil volcanic fields to the north, and the Sierra Madre and Trans-Pecos fields to the south and east. The caldera is a transitional calc-alkalic to alkalic magmatic system and in this respect is similar to other Cordilleran magmatic centers that formed after, or late during, the compressional phase of the mid-Tertiary calc-alkalic magmatic flare-up but prior to high-angle Basin and Range faulting and bimodal, dominantly alkali basaltic, volcanism. Comparable magmatic suites include the "silicic-alkalic" rocks of the Lake City and Questa calderas [Lipman, 1981] and the early extensional "alkali-calcic" belt of the southern Trans-Pecos and adjacent Chihuahua [McDowell and Clabaugh, 1979; Price et al., 1987; Henry et al., 1989], as well as early extensional rocks of the Mogollon-Datil field [Cather, 1990]. Each of these suites records the transition from compressional (subduction related) to extensional tectonics in the respective area.
Common traits of mantle plumes are:1) domal uplift prior to volcanism, 2) a definite age progression along a volcanic chain, 3) long mafic dikes that radiate from the volcanic core, 4) large basaltic plateaus or shield volcanoes, and 5) petrochemical indicators of anomalously high temperature melt zones in the upper mantle, such as high Ni/MgO ratios in picritic basalts (Campbell, 2001). We suggest the Socorro-Magdalena magmatic system of Oligocene age (Fig.1, eruptive volume 7100 km 3) exhibits characteristics similar to a mantle plume, but at 1/10-1/100 th the scale of a deep mantle plume, which may qualify it as a miniplume? A cluster of five overlapping ignimbrite calderas is moderately well exposed in strongly extended, tilted fault-block mountain ranges of the central Rio Grande rift southwest of Socorro NM (Fig.1). The westward younging Socorro-Magdalena caldera cluster (SMCC) is 85 km long and 20-25 km wide. It parallels the southeastern margin of the Colorado Plateau and the WSW-trending San Agustin arm of the rift. The latter produces the appearance of an incipient triple junction within the dominantly north-trending rift system. Precise 40 Ar/ 39 Ar ages of sanidines from the rhyolite ignimbrites and detailed geologic mapping demonstrate that the distended calderas become progressively younger to the west-southwest (McIntosh et al., 1991: Chamberlin et al., in press). Large volume ignimbrite eruptions occurred at 31.9, 28.7, 27.9, 27.4 and 24.3 Ma. A large satellitic caldera, which formed at 28.4 Ma, is located 20 km southwest of the main overlapping trend. A small collapse structure, which is nested in the Socorro caldera, erupted at 30.0 Ma. The total volume of densely welded ignimbrite and moat-fill lavas erupted from the SMCC is 5500 km 3. Within 40 km of the northeastern margin of the caldera cluster, the rhyolite ignimbrites are interleaved with a 400-700 m thick plateau-like belt of basaltic andesite lavas (Fig.1). These mafic lavas are assigned to the La Jara Peak Basaltic Andesite (Osburn and Chapin, 1983a). They range from slightly alkaline trachybasalt to moderately alkaline basaltic trachyandesite and sub-alkaline basaltic andesite. Sparse small phenocrysts of olivine, commonly altered to reddish brown iddingsite, are characteristic. Phenocrystic plagioclase, indicative of differentiation at depths less than 30 km (Wilson, 1989), is typically absent. Individual basaltic andesite flows are commonly 7-10 m thick. Stacked flows between ignimbrites have an aggregate thickness of as much as 330m and locally define wedge-shaped prisms formed by domino-style extension in the early Rio Grande rift (Chamberlin, 1983; Ferguson, 1991). A 32-33 Ma flow and tephra unit near La Joya was locally fed by a short NE striking basalticandesite dike that appears to radiate from the 31.9-Ma Socorro caldera (Fig1). A primitive trachybasalt in the SE moat of the Socorro caldera (~31 Ma; Chamberlin et al., in press) contains 9.3 % MgO and 170 ppm Ni; this suggests a relatively hot source zone in the mantle, compared to most subduction related basalts (Campbell, 2001). The total volume of Oligocene basaltic andesite lavas peripheral to the SMCC is 1600 km 3. The maximum rate of basaltic andesite eruption, ~1800 km 3 /Ma, was coeval with the zenith of domino-style extension and apparent caldera migration at 27.9-27.4 Ma. Moderately alkaline to sub-alkaline basaltic andesite and trachybasalt dikes of Oligocene age (31-24 Ma, K/Ar, Aldrich et al., 1986; Laughlin et al., 1983) form a large semi-continuous radial array that is broadly focused on the SMCC (Fig.1). The Magdalena radial dike swarm (MRDS) fans through
eastern sector of the Oligocene Socorro caldera, central Rio Grande rift, New Mexico
2004
Ar/ 39 Ar age determinations help provide a precise chronologic framework for volcanism in and near the 24kmdiameter Socorro caldera, previously established as the source of the 1,200 km 3 , phe nocrystrich Hells Mesa Tuff erupted at 31.9 Ma. The Socorro caldera is the easternmost member of a westwardyounging 31.9-24.3 Ma cluster of six large silicic calderas in the northern Mogollon-Datil volcanic field. Strongly east tilted fault blocks of the Rio Grande rift, within the Chupadera Mountains, provide a cross sectional view of the eastern sector of the Socorro caldera. New 40 Ar/ 39 Ar ages from this area, including 15 precise singlecrystal laserfusion ages from sani dinebearing rhyolites, suggest a somewhat unusual eruptive history for the Socorro caldera. Resurgent uplift and eruptive activity soon after caldera formation was minimal. Only one phe nocrystrich, 31.9 Ma, ringfracture lava dome has been identified. Significant uplift of the caldera core began shortly before 30.0 Ma probably about 1.5 Ma after caldera collapse. The moatfilling sequence (Luis Lopez Formation) consists of volcaniclastic sediments, phenocrystpoor rhyolitic tuffs, and basaltic to rhyolitic lavas. The basal sedimentary member is bracketed between 31.9 and 30.0 Ma. Two flowbanded rhyolite cobbles in this interval were dated at 33.7 Ma, suggesting derivation from an otherwise unknown precaldera lava flow near the southeast rim of the caldera. Following prolonged sedimentation, a primitive trachybasalt (9.3% MgO, 170 ppm Ni) ponded in the southeastern moat of the caldera shortly before 30.0 Ma. More differentiated basaltic andesite to andesite lavas were also erupted in the northeastern moat at about this time. Marked uplift and moderate east tilting of the central Socorro caldera occurred shortly before eruption of the basaltic lavas and before eruption of >10 km 3 of rhyolitic pumiceous tuffs in the medial Luis Lopez Formation at 30.0 Ma. Coarse lithicrich vent facies and thickness variations indicate that the upper pumiceous tuff was erupted from a small collapse structure nested within the central Socorro caldera northwest of Black Canyon (Black Canyon vent area). The pumiceous tuffs locally contain mafic rhyolite flows adjacent to the central horst block; these anomalously Crrich (70 ppm Cr) lowsilica rhyolite flows apparently represent mixing of basaltic andesite and silicic rhyolite magmas. Upwardcoarsening intermediate porphyry lavas, pri marily erupted from fissure vents in the northeast moat of the Socorro caldera, conformably overlie the pumiceous tuffs. At 28.8 Ma, rhyolitic activity in the eastern Socorro caldera intensified, erupting crystalpoor, highsilica rhyolite lava domes along preexisting ring fractures and intruding composi tionally similar rhyolite dikes along the north flank of the central horst block, south of Black Canyon. Emplacement of ringfracture lava domes was soon followed at 28.7 Ma by eruption of the 1,250 km 3 , phenocrystpoor, La Jencia Tuff and collapse of the Sawmill Canyon caldera, which obliterated most of the western sector of the Socorro caldera. A moderately porphyritic rhyolite dike exposed north of Black Canyon was emplaced at 28.3 Ma probably during resurgence of the Sawmill Canyon caldera. Lemitar Tuff dated at 27.8 Ma locally overlies the eastern wall of the Sawmill Canyon caldera where it truncates moat deposits of the Socorro caldera. One rhyolite dike in the study area, once thought to be related to Oligocene caldera volcanism, is actually 11.0 Ma and therefore related to volcanism along the Socorro accommodation zone, a transverse structural element of the Rio Grande rift. Crystallization trends, field relationships, and eruption age data imply that the 31.9 Ma Hells Mesa magma body crystallized within a few hundred thousand years after caldera collapse. Eruption of a primitive trachybasalt at about 30.5 Ma signaled initiation of a new crustal magmatic system that apparently evolved by fractionation, assimilation, and possibly more basaltic replenishment into the large rhyolite body that ultimately fed eruption of the La Jencia Tuff at 28.7 Ma. We suggest that sim ilar magmatic cycles in younger calderas to the west also represent periodic replenishment of the cen tral magmatic system by basaltic underplating associated with diapiric upwellings of asthenospheric upper mantle. SOCORRO CALDERA AT 28.7 MA (LOOKING EAST) Moat Spring Peak Mts. Outflow Rim Central Moat Rim Black Canyon horst Wall Ring Ring Wall vent area block (Collar) F.Z. fracture (Collar) (small caldera?) N S
A major resurgent caldera in southern Mexico: the source of the late Eocene Tilzapotla ignimbrite
Journal of Volcanology and Geothermal Research, 2004
The Tilzapotla caldera constitutes the first discovery of a major Tertiary collapse volcanic structure south of the Mexican Volcanic Belt. Although it is spatially associated with silicic ignimbrites in a region relatively distant from the extensive ignimbritic province of the Sierra Madre Occidental (SMO), it is among the largest collapse calderas documented in Mexico. The caldera is defined by a 33 Â 24 km semi-elliptical structure that encircles the largest exposures of the Tilzapotla ignimbrite and corresponds to the structural margin rather than the topographic rim. A central uplifted block limited by NW-trending faults is the main indication of a resurgent stage. The caldera structural margin is surrounded by extensive exposures of Cretaceous marine sequences that structurally define a broad elliptical dome (45 Â 35 km) originated in the first stage of the caldera evolution. There is evidence showing that the 34 Ma Tilzapotla ignimbrite represents the climatic event of the caldera collapse. It is constituted by a massive sequence of crystal vitric tuff with conspicuous euhedral biotite and abundant quartz. The intra-caldera facies is intercalated with mega-and meso-breccias of limestone and anhydrite fragments derived from the slumping of the caldera wall during the caldera collapse. The overlying sequence includes post-collapse ignimbrites as well as amphibole and pyroxene bearing dacitic to andesitic lava flows. The age (33 to 32 Ma) and isotopic signatures of these lava flows indicate a resurgent event related with the input of more primitive magmas into the magma chamber. The rectilinear northeastern and southwestern segments of the structural margin of the caldera correspond to NW-trending tectonic lineaments that are part of a regional strike-slip system, active at the time of the caldera formation. We interpret that the NW tectonic structures defined zones of weakness that accommodated the caldera collapse in the northeastern and southwestern segments of the caldera structural margin.
Timber Mountain–Oasis Valley caldera complex of southern Nevada
Geological Society of America Bulletin, 1977
The Timber Mountain-Oasis Valley caldera complex lies within a volcanic field in southern Nevada that once covered 11,000 km 2 . The caldera complex, active from 16 to 9.5 m.y. ago, was the source of nine voluminous rhyolitic ash-flow sheets and numerous smaller rhyolitic tuffs and lava flows. Several centers of basaltic and related volcanism were active before the complex formed, continued around its periphery during caldera activity, and have since overlapped the caldera complex. Extensional normal faulting and perhaps deep-seated right-lateral deformation preceded, accompanied, and followed evolution of the caldera complex and its surrounding volcanic field.
Journal of Volcanology and Geothermal Research, 2002
An area of widespread alkaline-to-subalkaline volcanism lies at the northern end of the Cofre de PeroteĈ itlalte ¤petl (Pico de Orizaba) volcanic chain in the eastern Mexican Volcanic Belt (MVB). Two principal areas were active. About a dozen latest-Pleistocene to precolumbian vents form the 11-km-wide, E^W-trending Cofre de Perote vent cluster (CPVC) at 2300^2800 m elevation on the flank of the largely Pleistocene Cofre de Perote shield volcano and produced an extensive lava field that covers s 100 km 2 . More widely dispersed vents form the Naolinco volcanic field (NVF) in the Sierra de Chiconquiaco north of the city of Jalapa (Xalapa). Three generations of flows are delineated by cone and lava-flow morphology, degree of vegetation and cultivation, and radiocarbon dating. The flows lie in the behind-the-arc portion of the northeastern part of the MVB and show major-and trace-element chemical patterns transitional between intraplate and subduction zone environments. Flows of the oldest group originated from La Joya cinder cone (radiocarbon ages V42 000 yr BP) at the eastern end of the CPVC. This cone fed an olivine-basaltic flow field of V20 km 2 that extends about 14 km southeast to underlie the heavily populated northern outskirts of Jalapa, the capital city of the state of Veracruz. The Central Cone Group (CCG), of intermediate age, consists of four morphologically youthful cinder cones and associated vents that were the source of a lava field s 27 km 2 of late-Pleistocene or Holocene age. The youngest group includes the westernmost flow, from Cerro Colorado, and a lava flow V2980 BP from the Rinco ¤ n de Chapultepec scoria cone of the NVF.
Intracaldera volcanic activity, Toledo Caldera and Embayment, Jemez Mountains, New Mexico
Journal of Geophysical Research, 1986
The Toledo caldera was formed at 1.47 ± 0.06 Ma during the catastrophic eruption of the lower member Bandelier Tuff. The caldera was obscured at 1.12 ± 0.03 Ma during eruption of the equally volumin~us upper member of the Bandelier Tuff that led to formation of the Valles caldera. Earlier workers interpreted a 9-km-diameter embayment, located NE of the Valles caldera (Toledo embayment), to be a remnant of the Toledo caldera. Drill hole data and new K-Ar dates of Toledo intracaldera domes redefine the position of Toledo caldera, nearly coincident with and of the same dimensions as the younger Valles caldera. The Toledo embayment may be of tectonic origin or a small Tschicoma volcanic center caldera. This interpretation is consistent with distribution of the lower member of the Bandeher Tuff and with several other field and drilling-related observations. Explosive activity associated with Cerro Toledo Rhyolite domes is recorded in tuff deposits located between the lower and upper members of the Bandelier Tuff on the northeast flank of the Jemez Mountains. Recorded in the tuff deposits are seven cycles of explosive activity. Most cycles consist of phreatomagmatic tuffs that grade upward into Plinian pumice beds. A separate deposit, of the same age and consisting of pyroclastic surges and flows, is associated with Rabbit Mountain, located on the southeast rim of the Valles-Toledo caldera complex. These are the surface expression of what may be a thicker, more voluminous intracaldera tuff sequence. The combined deposits of the lower and upper members of the Bandelier Tuff, Toledo and Valles intracaldera sediments, tuffs, and dome lavas form what we interpret to be a wedge-shaped caldera fill. This sequence is confirmed by "deep drill holes and gravity surveys. This fill accumulated in depressions formed during precaldera rifting and episodes of caldera collapse. We interpret the Toledo-Valles caldera complex to be a pair of nearly coincident trapdoor calderas, with the hinge on the west side and thick caldera fill in the east.
Bulletin of Volcanology, 1988
The Yampa and Elkhead Mountains volcanic fields were erupted into sediment-filled fault basins during Miocene crustal extension in NW Colorado. Post-Miocene uplift and erosion has exposed alkali basalt lavas, pyroclastic deposits, volcanic necks and dykes which record hydrovolcanic and strombolian phenomena at different erosion depths. The occurrence of these different phenomena was related to the degree of lithification of the rocks through which the magmas rose. Hydrovolcanic interactions only occurred where rising basaltic magma encountered wet, porous, non-lithified sediments of the 600 m thick Miocene Brown's Park Formation. The interactions were fuelled by groundwater in these sediments: there was probably no standing surface water. Dykes intruded into the sediments have pillowed sides, and local swirled inclusions of sediment that were injected while fluidized in steam from heated pore water. Volcanic necks in the sediments consist of basaltic tuff, sediment blocks and separated grains derived from the sediments, lithic blocks (mostly derived from a conglomerate forming the local base of the Brown's Park Formation), and dykes composed of disaggregated sediment. The necks are cut by contemporaneous basalt dykes. Hydrovolcanic pyroclastic deposits formed tuff cones up to 100 m thick consisting of bedded air-fall, pyroclastic surge, and massive, poorly sorted deposits (MPSDs). All these contain sub-equal volumes of basaltic tuff and disaggregated sediment grains from the Brown's Park Formation. Possible explosive and effusive modes of formation for the MPSDs are discussed. Contemporaneous strombolian scoria deposits overlie lithified Cretaceous sedimentary rocks or thick basalt lavas. Volcanic necks intruded into the Cretaceous rocks consist of basalt clasts (some with spindle-shape), lithic clasts, and megacrysts de-rived from the magma, and are cut by basalt dykes. Rarely, strombolian deposits are interbedded with hydrovolcanic pyroclastic deposits, recording changes in eruption behaviour during one eruption. The hydrovolcanic eruptions occurred by interaction of magma with groundwater in the Brown's Park sediments. The explosive interactions disaggregated the sediment. Such direct digestion of sediment by the magma in the vents would probably not have released enough water to maintain a water/magma mass ratio sufficient for hydrovolcanic explosions to produce the tuff cones. Probably, additional water (perhaps 76% of the total) was derived by flow through the permeable sediments (especially the basal conglomerate to the formation), and into the vents.