Resurgent Cauldrons Research Articles

Ring Structures, Resurgent Cauldron, and Ore Deposits in the Hokuroku Volcanic Field, Northern Akita, Japan*

Ring dikes, normal faults, central uplift, and slumping structure are considered to be the key factors of the submarine resurgent cauldron. In the east Odate area, there occurs a ring distribution of post-Kuroko dacites and epithermal ore deposits around the central Otaki quartz diorite. Vein-type and Kuroko deposits are distributed almost along the half of the ring. There also occur submarine slumping structures. The estimated sub- surface structure indicates the central uplifting and marginal depression in the inside of ring dacites. Those phe- nomena are interpreted as the fossil submarine resurgent cauldron in the Miocene age with the intermediate scale of about 8 kilometers in horizontal diameter, associated with the genesis of Kuroko deposits and epithermal veins. A structural model of the relationship between the processes of a cauldron formation and ore genesis is proposed.

Ignimbritic cauldrons, alkali granites, and mineral deposits in fault-block mountains

The term fault-block mountains refers to an orogen, formed in an ensialic back arc by extension. The voluminous magmatism due to underplating of hot oceanic lithosphere, extrem thinning of the continental lithosphere and partial melting as well as mantle diapirs will be examplified by three ore provinces: 1. Southwestern North America (Middle Tertiary peralkaline ignimbrites and resurgent cauldrons) 2. Central Iran (Infracambrian ignimbrites and riebeckitegranite) 3. Arabian Shield (Infracambrian alkaligranites and rhyolites, 625-570 m.y.).

The Mount Morgan gold-copper mine and environment, Queensland; a volcanogenic massive sulfide deposit associated with penecontemporaneous faulting

The Mount Morgan mine was closed in July 1981, having yielded 237,896 kg of gold (7,648,533 oz) and 360,616 metric tons of copper from 50 million metric tons of ore, an average recovered grade of 4.75 g/metric ton Au and 0.72 percent Cu. It has been Australia9s largest single lode gold orebody and is the fourth largest gold-producing area after the Kalgoorlie Golden Mile and the Bendigo and Ballarat areas (Woodall, 1979).The mine comprises the Main Pipe orebody of pyritic massive sulfides and the adjacent Sugarloaf orebody of siliceous stringer mineralization. When the host stratigraphy is reoriented with respect to regional dip and local faulting, the two orebodies are shown to form a pipelike volcanogenic massive sulfide configuration at a high angle to the stratigraphy.Minor stratiform pyritic mineralization adjacent to the stratigraphic top of the orebody grades downdip away from the orebody to a sequence of interbedded crystal tuffs and cherty rocks with some jasperoid beds.The associated alteration halo of the massive sulfide orebody has been intruded by the Late Devonian Mount Morgan Tonalite. The ore and alteration have been subjected to metamorphism and overprinted by later alteration and additional mineralizing phases, mostly related to the complex tonalite intrusion.The immediate host stratigraphy shows gross thickening and change of character on either side of the orebody, suggesting that the orebody formed along a penecontemporaneous fault. The fault appears to be part of a major resurgent cauldron structure.

Mid‐Tertiary ash flow tuff cauldrons, southwestern New Mexico

This summary characterizes 28 known or suspected mid‐Tertiary ash flow tuff (ignimbrite) cauldrons, up to 40 km in diameter, in southwestern New Mexico. A combination of postcauldron block faulting and erosion has resulted in widely ranging levels of three‐dimensional exposures, down to plutonic roots. The evolution of the largest resurgent cauldrons followed the course determined by other workers for the Valles caldera (New Mexico) and Lake City cauldron (Colorado), with local variations. Five principal stages can be recognized: (1) precursor, (2) caldera collapse, (3) early post‐collapse volcanism, (4) major ringfracture volcanism, and (5) hydrothermal activity. Development can be terminated at any stage; stages can also be repeated. Resurgent doming can occur during stage 3 or later; doming can also be enhanced by reactivation of cauldron structures by postvolcanic basin and range faulting. Even where the surface of caldera‐fill tuff is domed, the base may have quite a different configuration. Recognition of resurgent doming may be difficult in deeply eroded cauldrons. A proposed modification in the definition of “resurgence” places emphasis on one or more magma pulses after a caldera‐forming eruption; doming is one of several effects that may or may not occur when magma invades a previously subsided cauldron. In some cauldrons, postcollapse lavas can be divided into (1) “cauldron lavas,” i.e., relatively mafic crystal‐rich disequilibrium assemblages derived from shallow defluidized residues of caldera‐forming ash flow tuff eruptions, and (2) “framework lavas,” i.e., relatively siliceous crystal‐poor near‐equilibrium assemblages derived from an evolving siliceous pluton at deeper levels, below the cauldron complex. Special features of New Mexico cauldrons include zoned outflow sheets; zoning may be normal (most siliceous at the bottom) or reversed. Posteruption potassium metasomatism may mask some chemical trends. Several styles of eruption can be recognized among mid‐Tertiary cauldrons of southwestern New Mexico. The largest ones tend to occur in clusters, interpreted as surface expressions of buried composite plutons (e.g., Mogollon Plateau). In an early stage of development, or on the fringe of a cluster, cauldrons tend to be asymmetrical trapdoor structures, formed by repeated small eruptions separated by quiescent periods. During the height of activity, cauldrons formed by eviscerating eruptions, commonly followed by resurgence. The youngest known cauldron is shallow and resulted from asymmetrical subsidence and collapse of caldera walls.

The regional geology and evolution of the Toba volcano-tectonic depression, Indonesia

The late Quaternary Toba volcano-tectonic depression, in the Sunda Arc, is the largest resurgent cauldron in the world and lies in one of the largest ignimbrite fields, the Toba Tuffs. Although composed of at least 3000 km 3 of acid tuffs, spread over 20000 km 2 of mainland Sumatra, the greater part of the Toba Tuffs is believed to be a single ignimbrite cooling unit, formed about 100,000 years ago. The Toba Tuffs also include a 30000-year-old airfall tuff, which was erupted from a centre just N of the Toba depression. The Toba depression developed through the same stages as other resurgent cauldrons. It formed after lithification of the Toba Tuffs, by collapse along regional faults crossing an eastwards bulge in the Sumatran geanticline. Resurgent uplift raised lake sediments within the depression by about 500 m. The uplift, which was not confined to the depression, was probably caused by continuing influx of magma and it is possible that the Toba depression is still in the stage of post-resurgence volcanism. The eruption of the Toba Tuffs and of all post-ignimbrite volcanism took place on the line of the western marginal fault of the depression. This marginal fault once extended northwards offshore into a zone of Miocene back-arc rifting.

Tertiary Volcanic Centers as Constraints on Oil and Gas Potential of Basin and Range Province: New Mexico Segment of Pedregosa Basin: ABSTRACT

Stratigraphic similarities with the Permian basin and structural similarities with the Overthrust belt make the New Mexico segment of the Pedregosa basin an attractive target for petroleum exploration. Middle Tertiary volcanic cover and postvolcanic faults introduce constraints, as elsewhere in the Basin and Range province. Geologic mapping in southwesternmost New Mexico (Hidalgo County) has traced Oligocene ash-flow tuff sheets to at least nine major cauldrons, including Valles-type resurgent cauldrons 10 to 40 km wide (Apache Hills: Apache cauldron; southern Pyramid Mountains: Muir cauldron; southern Animas Mountains: Tullous, Juniper, Animas Peak, Cowboy Rim, San Luis cauldrons; southern Peloncillo Mountains: Rodeo and Geronimo Trail cauldrons). Faulted-off cauldron segments continue beneath the Playas, Animas-San Luis, and San Simon-San Bernadino Valleys. Composite batholiths probably underlie cauldron clusters, as in the San Juan and Mogollon-Datil volcanic fields. Exposed monzonitic plutons (Apache Hills, Pyramid Mountains, Animas Mountains) are apophyses, emplaced during resurgence. Other plutons, apparently unrelated to cauldrons, are present in the northern Pyramid and Little Hatchet Mountains. Distribution of cauldrons and plutons suggests that much of the Pyramid, Peloncillo, Little Hatchet, and Animas Mountains, Apache Hills, and adjacent valleys are unfavorable for petroleum accumulations. However, destructive thermal effects may be confined to aureoles extending only about 1,000 m from intrusive contacts, as in the KCM 1 Forest Federal wildcat. Cauldrons and thermal effects deleterious to petroleum potential are unknown in so theastern Hidalgo County (Dog, Alamo Hueco, Big Hatchet Mountains, southern Sierra Rica). End_of_Article - Last_Page 759------------

A resurgent cauldron in the early Paleozoic of Wales, U.K.

Abstract The paper presents a controversial interpretation of a mid-Ordovician volcano-sedimentary complex. It deals with the cyclic interdependence of intrusive, volcanic, and sedimentary processes, due to the development of a nearshore resurgent cauldron in the Caledonian fold belt of North Wales. Deformed volcanotectonic features include a resurgent dome and apical graben, surrounded by a moat and peripheral crescentic ring-fault, constituting a caldera 20 km in diameter. The resurgent Snowdon caldera developed through three cycles of ash-flow volcanism resulting from the continuous supply of magma into a shallow magma chamber emplaced beneath the floor of a marine basin. Each ash-flow cycle was preceded by the emergence, above sea level, of a geotumour that subsequently collapsed following eruption and evacuation of the magma chamber. Localized unconformities at the base of individual ash-flow cycles are compared with caldera margin and associated collapse features. Deeper-seated effects of caldera collapse are expressed as gaps in the Ordovician sequence due to normal faulting along the structural boundary of the caldera. Major ash-flow fissure vents were located at points of maximum unloading of the magma chamber by distention faults in its roof. Explosive mechanisms were triggered by rapid pressure release due to tectonic erosion. The presence of a resurgent cauldron implies that the Ordovician succession of North Wales is more complete than recorded in the literature, and that Caledonian structures were largely predetermined by Caradocian volcano-tectonics.

Granitic ring complexes and Precambrian hot-spot activity in the St. Francois terrane, Midcontinent region, United States

Surface and subsurface geologic data have led to the recognition of granitic ring complexes in the 1.5-b.y.-old St. Francois terrane of southeastern Missouri. The distinctive rock association of the ring complexes comprises alkaline silicic rocks with minor quartz monzonite, trachyte, and basalt. Three periods of granite emplacement are recognized: sub-volcanic granite massifs were emplaced below comagmatic rhyolites and ash-flow tuffs, quartz monzonite and associated hypabyssal rocks were intruded along ring fractures in cauldron-subsidence structures, and central plutons were emplaced in resurgent cauldrons. Similar magmatic complexes in the buried Precambrian basement of the Midcontinent indicate a period of widespread anorogenic magmatism that may have been induced by intraplate hot-spot activity. The post-Precambrian geologic record of the region suggests that recurrent, but localized and less intense, hot-spot activity was responsible for emplacements of alkaline ultramafic rocks, for tectonic adjustments, and for increased geothermal gradients that created favorable ore-concentrating environments in the sedimentary rocks.

Gravity and aeromagnetic anomalies over basement structure in the Rolla Quadrangle and the southeast Missouri lead district

Regional geologic, stratigraphic, geochemical, remote sensing, and geophysical studies of the Rolla 1 degrees X 2 degrees quadrangle, Missouri, are in progress by the U. S. and Missouri Geological Surveys. Reconnaissance gravity data are available throughout the quadrangle and aeromagnetic data are available over its eastern part. A prominent north-west-trending gravity gradient, attributed in part to deep crustal structure, crosses the entire map. Otherwise, the major geophysical anomalies are subcircular features 10 to 40 km in diameter. There is no expression geophysically of gridded fault block structure.A positive gravity anomaly near Salem indicates a shallow intrabasement mafic or ultramafic body (density 3.0-3.2 g/cm 3 ) about 13 km in diameter and 2 to 4 km thick. Prominent gravity and magnetic lows near Belleview and Hawn State Park are attributed to granite plutons. Gravity lows of unknown but probably intrabasement origin occur near Steelville and Spring Valley. Model studies of the Hawn State Park anomalies lead to a doughnut-shaped anomalous mass distribution suggestive of a ring dike and associated resurgent cauldron about 25 km in diameter. On the other hand, the Taum Sauk caldera, a feature inferred from geological field studies, shows no gravity or magnetic expression of an associated pluton, suggesting the feature may be a volcano-tectonic depression but probably is not a caldera.

Resurgent Volcano-Tectonic Depression of Oligocene Age, South-Central New Mexico

The Goodsight-Cedar Hills volcano-tectonic depression in south-central New Mexico formed concurrently with and following deposition of about 550 km 3 of Oligocene volcanic and volcaniclastic rocks. The depression is an asymmetric basin about 80 km long and 38 km wide. It is filled to a maximum depth of about 550 m by early rhyolitic ash-flow tuff, medial epiclastic strata derived partly from marginal raised rims (Bell Top Formation), and late basaltic andesite (Uvas Basalt). Much of the 295 km 3 of effusive rock was erupted from vents located near the center of the depression and from a major subsidence fracture zone along the eastern margin. Subsidence of the depression floor was noncatastrophic and approximately kept pace with basin filling, except along the eastern margin. Following eruption and broad, regional subsidence of the Uvas Basalt, the central floor of the depression was arched upward to form the Sierra de las Uvas dome and adjacent synclinal moat. The fault pattern of the dome and its association with known vents and the thickest part of the volcanic pile suggest that it formed by vertical movement of magma from an underlying chamber. Its development, following subsidence of the Uvas Basalt, suggests that it is essentially resurgent in origin. Although no postdoming volcanism is known, indirect evidence indicates that intrusion of silicic magma probably caused resurgence. It is clear that the Goodsight-Cedar Hills depression is not a resurgent cauldron of the classic Valles or Toba types. Rather, it appears to be a structure transitional in character between a cauldron and a fault trough. Subsidence apparently followed volcanism. Resurgence followed eruption of basaltic andesite rather than the usual ash-flow sequence, and the 10- to 12-m.y. history of the Goodsight-Cedar Hills depression is 5 to 6 times as long as other well-known resurgent cauldron cycles. Locally, deposition in the depression continued without interruption into early late Tertiary time, when extensional faulting occurred. The depression is elongated parallel to the late Tertiary Rio Grande Rift and may be a precursor of Basin and Range structure in the area. The late Tertiary fault pattern in the area indicates that earlier volcano-tectonic structures had important effects on the pattern of late Tertiary Basin and Range structures. Locally, late Tertiary faults were inherited from and duplicate the position of earlier subsidence faults or the synclinal moat. Elsewhere, the north-trending regional fault pattern was considerably modified by structural and litho-logic inhomogeneities of volcano-tectonic origin, particularly the Sierra de las Uvas dome and its buried intrusive masses.

A tertiary silicic cauldron complex at the northern margin of the basin and range province, central Arizona, U.S.A.

The Superior volcanic field occupies approximately 8,000 square kilometers of central Arizona in the zone between the southern Basin and Range Province and the Colorado Plateaus Province. The primary structural elements of an eruptive center in the western part of this field are: 1) volcanic plateau, 2) ring fracture zone, and 3) resurgent caldera core. A northwest trending graben controls the location of three small subsided blocks, the Willow Springs cauldron (2 km diameter), the Black Mesa cauldron (4 km diameter), and the Florence Junction cauldron (8 km diameter), which were centers for rhyolite ash and lava eruption. These late features are superimposed on a much larger volcano-tectonic structure, the Superstition resurgent cauldron which subsided at an earlier stage following the extrusion of quartz latite welded tuff.

Some Tectonic Aspects of Quaternary Volcanoes in Japan

Part 1 of this paper is concerned with various types of deformation of volcanic cones as listed in Table 1. In regard to the crustal displacements before and after eruptions, the local upheaval and fracturing near crater remain as a permanent deformed topography, but the areal upheaval and subsidence before and after eruption are believed to be a reiterative movement caused by increase and decrease of the pressure in magma reservoir. Most of collapse calderas in Japan belong to Krakatoan type and some to Kilauean type, but none of resurgent cauldrons is known. These deformations of volcanic origin are generally circular in their horizontal shape and display larger magnitude and rate in vertical displacement than those of non-magmatic gravitational and tectonic origin.Non-magmatic, superficial, gravitational deformation of volcanic cones such as the settlement of cones and landslides of large scale are emphasized, because of their important role to deform volcanic cones on the weak foundations such as Cenozoic altered volcanics. It is also known that non-magmatic tectonic movements such as the active faulting connected with earthquakes, the active folding of the basement etc., deform volcanic cones.In part 2, firstly, horizontal arrangement of volcanoes is separated into three types of different extent. Two volcanic zones, East Japan and West Japan, are recognized. The two display remarkable cross-sectional asymmetry of both volume of volcanic products and nature of magma from oceanic side to continental side. This asymmetry is believed to be due primarily to the continental-ward inclination of the mantle earthquake zone where parental magma generates. Volcanic center alignments are in parallel with mountain ranges of about 50km in width and are related to the pre-existing faults which were formed during the mountain building. Volcanic vent alignments run in perpendicular or diagonal direction to the volcanic center alignments and are inferred to be related to tension cracks parallel to the late Quaternary local principal horizontal stress direction.Secondly, the vertical distribution of volcanoes of different ages in relation to the configurations of their basements is discussed (Figs. 1, 2, 3, 4). Older volcanoes which were formed during middle and early Quaternary usually rest on the crest of the rised or rising mountain ranges. On the contrary, younger volcanoes which are active during late Quaternary tend to occur on the relatively lower places than older volcanoes.The last chapter is devoted to deal with relationship between the distribution of Quaternary volcanoes of different ages and neotectonics in Japan. Fig. 5 shows a possible working hypothesis on the relationship.