Download or read book Arc rift Transition Volcanism in the Volcanic Hills Jacumba and Coyote Mountains San Diego and Imperial Counties California written by and published by . This book was released on 2014 with total page 76 pages. Available in PDF, EPUB and Kindle. Book excerpt: Neogene volcanism associated with the subduction of the Farallon-Pacific spreading center and the transition from a subduction zone to a rift zone has been studied extensively in Baja, California, Mexico. One of the main goals of these studies was to find a geochemical correlation with slab windows that may have formed during that complicated transition. While workers have been able to find distinct geochemical signatures in samples from Baja California, none have shown statistically significant correlation with samples from southern California that are thought to be related to the same arc-rift transition events. All of the basaltic samples from this study of southern California rocks have prominent Nb depletions typical of island-arc subduction-related volcanism, in contrast to the chemistry of Baja California volcanics that have trace element patterns typical of synrift related volcanism. The work done by previous investigators has been additionally complicated due to each investigator's choice of important ratios or patterns, which bears little, if any, correlation with work done by others working in the same area. For example, some workers use K/Rb ratios in their study of the Puertocitos Volcanic Province, while others argue that Sr/Y vs. Y is a better indicator of petrogenetic processes. Little petrologic work has been done on Neogene volcanic rocks in the Imperial Valley and eastern San Diego County region of Southern California. This thesis combines new research with that of previous workers and attempts to establish a better understanding of the processes involved with the transition volcanism. Prior work documents significant differences in the geochemistry between some of these areas, especially those in close proximity to each other (e.g. the Volcanic Hills and Coyote Mountains). These differences were thought to be largely the result different magmatic sources. The potential of finding two differing magma types in close proximity could possibly reflect the opening of a slab window produced by the collision of the spreading center and continued subduction of the Farallon plate beneath the North American continent. However, evidence presented here suggests that crustal contamination and metasomatic processes in the Coyote Mountains are the primary source of the geochemical variations. Trace-element signatures are similar in samples from all of the study regions, with pronounced Nb depletion typical of island-arc volcanism. The distinguishing features of samples from the Coyote Mountains are the high amount of alteration and their high levels of K2O (4-5 wt%). This study will examine the possibility that these characteristics result from the interaction of the basalt with a highly alkaline body of water and/or sediments. Supporting data for such a model include pillow structures and spiracle formations within the basalt flows exposed in the Fossil Canyon and Butaca Canyon regions of the Coyote Mountains. Future studies of the olivine-basalt samples within the central region of the Coyote Mountains, away from the altered exposures, would provide a more complete understanding of their genesis. While the geochemical data were initially analyzed using standard geochemical techniques, the data are also analyzed statistically using a relatively new multivariate analysis technique known as Compositional Data Analysis (CoDA). Using the CoDA techniques, a clearer insight into the actual changes of the chemical composition can be seen. It also provides statistically valid correlation between the various regions in the study area. The CoDA processes, CLR BiPlots in particular, show which elements vary from one region to the next. It also differentiates elemental groups that correlate with typical rock-forming processes (e.g., fractional crystallization) from those that result from contamination from other sources or processes. Two examples illustrate the application: 1) In the Volcanic Hills, a pronounced negative correlation between MgO and K2O is clearly observed. However, in the Table Mountain samples, there is less negative correlation observed between those same oxides, but a pronounced lack of correlation between MgO and P2O5, which may indicate magma mixing. 2) Samples from the Volcanic Hills show two distinct groups with similar variance values and strong correlation, but are negatively correlated with each other. The first group consists of those the elements that comprise the minerals that crystalize at high temperatures, such as, Mg, Fe and Ca. This is consistent with the formation of olivine, pyroxene and Ca-rich plagioclase, respectively. The second group shows the elements that comprise the lower temperature minerals such as more Na-rich plagioclase and orthoclase. These include, Na, Al, K, and Si.
Download or read book Field Excursions in Southern California written by Brian Kraatz and published by Geological Society of America. This book was released on 2017-08-28 with total page 260 pages. Available in PDF, EPUB and Kindle. Book excerpt: "This guidebook volume for the 2016 GSA Cordilleran Section Meeting, which was held in Ontario, California, explores varied geological features of southern California and Nevada, including the Mojave Desert and Tule Springs Fossil Beds National Monument"--
Download or read book Post batholithic Geology of the Volcanic Hills and Vicinity San Diego County California written by Robert Fourt and published by . This book was released on 1979 with total page 132 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Volcano Hazards of the Lassen Volcanic National Park Area California written by and published by . This book was released on 2000 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book South Cascades Arc Volcanism California and Southern Oregon written by L. J. Patrick Muffler and published by American Geophysical Union. This book was released on 1991-01-08 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Published by the American Geophysical Union as part of the Field Trip Guidebooks Series, Volume 312. The Cascade Range is a late Tertiary and Quternary volcanic arc that extends north from northeastern California through Oregon and Washington into British Columbia. The volcanic arc lies above an easterly dipping active subduction zone along which the Juan de Fuca, Gorda, and Explorer plates are thrust beneath the North American Plate (Riddington, 1984). In Addition to the major composite volcanoes that have erupted andesites, dacites, and even rhyolites, there are many smaller, commonly monogenetic vents that erupted primarily calc-alkaline basalt and basaltic andesites throughout the history of the arc (McBirney, 1978; Luedke and Smith, 1981, 1982; Smith and Luedke, 1984; Guffanti and Weaver, 1988). The volcanic arc is active, with certain historic eruptions at Lassen Peak (1914-17) and Mount St. Helens (mid-1800's; 1980-86), and possible historic eruptions at Mt. Shasta (1786), Mt. Baker (mid-1800's), Mt. Hood (mid-1800's), Mt. Rainier (mid-1800's) and Cinder Cone (east of Lassen Peak; 1851?).
Download or read book The Role of Volatiles in the Genesis Evolution and Eruption of Arc Magmas written by G.F. Zellmer and published by Geological Society of London. This book was released on 2015-03-17 with total page 294 pages. Available in PDF, EPUB and Kindle. Book excerpt: The subduction zone volatile cycle is key to understanding the petrogenesis, transport, storage and eruption of arc magmas. Volatiles control the flux of slab components into the mantle wedge, are responsible for melt generation through lowering the solidi of mantle materials and influence the crystallizing phase assemblages in the overriding crust. Further, the rates and extents of degassing during magma storage and decompression affect magma rheology, ultimately control eruption style and have consequences for the environmental impact of explosive arc volcanism. This book highlights recent progress in constraining the role of volatiles in magmatic processes. Individual book sections are devoted to tracing volatiles from the subducting slab to the overriding crust, their role in subvolcanic processes and eruption triggering, as well as magmatic-hydrothermal systems and volcanic degassing. For the first time, all aspects of the overarching theme of volatile cycling are covered in detail within a single volume.
Download or read book Volcanic and Sedimentary Facies Processes and Tectonics of Intra arc Basins written by Benjamin Nickolas Fackler-Adams and published by . This book was released on 1997 with total page 372 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Response Plan for Volcano Hazards in the Long Valley Caldera and Mono Craters Region California written by David P. Hill and published by Geological Survey (USGS). This book was released on 2002 with total page 68 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Volcanic and Nonmarine Stratigraphy of Southwest Isla Tiburon Gulf of California Mexico written by Jay Robert Neuhaus and published by . This book was released on 1989 with total page 384 pages. Available in PDF, EPUB and Kindle. Book excerpt: Southwestern Isla Tiburon (SWIT), Gulf of California, Mexico, is an area approximately 30 square kilometers, containing sedimentary and volcanic strata which are predominantly Early and Middle Miocene in age. A fossiliferous marine conglomerate on SWIT is believed the oldest marine deposit in the Gulf of California region, and supports the conclusion that a marine protogulf existed 15 to 8 Ma. K-Ar ages from this and previous studies provide a time constraint on the deposition of the marine conglomerate and the overall volcanic history of SWIT. Dips of beds suggest listric faulting occurred throughout much of the Miocene: Redbeds dip 40-50°N, basalt flows 23oN, conglomerates 20oN, and an ignimbrite 5oNW. A fault along Arroyo II displays right-lateral, strike slip and may be related to the La Cruz Fault which trends NW-SE along the southwest end of the island. In the late Cretaceous-early Tertiary, SWIT was part of the arc system along the western margin of the North American Plate. At this time, SWIT was adjacent to northeastern Baja California. In the Early Miocene Basin and Range extension led to the formation of small trough-shaped basins, and fluvio-lacustrine deposition resulted. Volcanic and roof pendant debris was shed into small basins on SWIT from the north. At 21-19 Ma andesitic volcanism occurred and a volcanic collapse structure formed which was later filled with andesitic lahar. The andesitic magma apparently formed out of a primary melt of the lower crust. From 19-16 Ma basaltic volcanism was dominant on SWIT and both tabular flows and ring dikes developed. The basalt of SWIT is alkalic olivine-augite, is high in incompatible elements and is similar to Early and Middle Miocene basalts of the Imperial Valley-northeastern Baja California region. Dacitic pyroclastic volcanism followed basaltic volcanism on SWIT, and between 14 and 11 Ma a protogulf developed which was filled with pyroclastic and conglomerate debris. At 11 Ma volcanism on SWIT became predominantly rhyolitic. First, rhyolite ignimbrite extruded, and, in the late Miocene, rhyolite pods, coulees, and crystal dikes developed. In the early Pliocene a dacitic ignimbrite with a tholeiitic character extruded reflecting conditions associated with modern Gulf of California rifting and seafloor spreading.
Download or read book Arc Volcanism written by Shigeo Aramaki and published by Elsevier Publishing Company. This book was released on 1983 with total page 664 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Role of Volcanism in Climate and Evolution written by Daniel I. Axelrod and published by Geological Society of America. This book was released on 1981-01-01 with total page 66 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Central Sierra Nevada Volcanic Field of California written by Marlon Mauricio Jean and published by . This book was released on 2007 with total page 134 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Geologic Field trip Guide to the Lassen Volcanic National Park and Vicinity written by Leroy J. Patrick Muffler and published by . This book was released on 2015 with total page 67 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Ancestral Cascade Arc Volcanism in the North Central Sierra Nevada California written by Rohit Kumar Sharma and published by . This book was released on 2008 with total page 118 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Geochemical Transition from Miocene Pliocene to Quaternary Arc Volcanism in the Sierra Nevada Nothern California written by Albert Jacob Stoffers and published by . This book was released on 2010 with total page 232 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Tectonic Versus Volcanic Origin of the Summit Depression at Medicine Lake Volcano California written by and published by . This book was released on 2010 with total page 62 pages. Available in PDF, EPUB and Kindle. Book excerpt: Medicine Lake Volcano is a Quaternary shield volcano located in a tectonically complex and active zone at the transition between the Basin and Range Province and the Cascade Range of the Pacific Province. The volcano is topped by a 7x12 km elliptical depression surrounded by a discontinuous constructional ring of basaltic to rhyolitic lava flows. This thesis explores the possibility that the depression may have formed due to regional extension (rift basin) or dextral shear (pull-apart basin) rather than through caldera collapse and examines the relationship between regional tectonics and localized volcanism. Existing data consisting of temperature and magnetotelluric surveys, alteration mineral studies, and core logging were compiled and supplemented with additional core logging, field observations, and fault striae studies in paleomagnetically oriented core samples. These results were then synthesized with regional fault data from existing maps and databases. Faulting patterns near the caldera, extension directions derived from fault striae P and T axes, and three-dimensional temperature and alteration mineral models are consistent with slip across arcuate ring faults related to magma chamber deflation during flank eruptions and/or a pyroclastic eruption at about 180 ka. These results are not consistent with a rift or pull-apart basin. Limited subsidence can be attributed to the relatively small volume of ash-flow tuff released by the only known major pyroclastic eruption and is inconsistent with the observed topographic relief. The additional relief can be explained by constructional volcanism. Striae from unoriented and oriented core, augmented by striae measurements in outcrop suggest that Walker Lane dextral shear, which can be reasonably projected from the southeast, has probably propagated into the Medicine Lake area. Most volcanic vents across Medicine Lake Volcano strike north-south, suggesting they are controlled by crustal weakness related to Basin and Range extension. Interaction of dextral shear, Basin and Range extension, and the zone of crustal weakness expressed as the Mount Shasta-Medicine Lake volcanic highland controlled the location and initiation of Medicine Lake Volcano at about 500 ka.
Download or read book Geology of the Monowai Rift Zone and Louisville Segment of the Tonga Kermadec Arc written by Alexandra Gray and published by . This book was released on 2022 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The Tonga-Kermadec arc in the SW Pacific comprises a chain of more than 90 volcanic complexes. A continuous 400-km long chain of volcanic activity along the central portion of the Tonga arc has become the focus of intensive research, extending previous studies that have focused on the southern Kermadec chain. Earlier interpretations of the Tonga arc have focused on a perceived lack of volcanism between ~21°S and ~27°S, adjacent to a bend in the trench caused by the collision of the subducting Louisville Seamount Chain (LSC). During swath mapping in 2002, it was revealed that this portion of the arc, including the Louisville and Monowai segments, is in fact one of the most volcanically active parts of the Tonga-Kermadec system. At this location, a combination of oblique convergence of the Pacific Plate and southward compression due to the collision of the LSC has resulted in left-lateral strike-slip faulting and rifting of the arc crust. This has produced a series of left-stepping arc transverse graben and horst structures that localize the voluminous volcanic activity. For this study, a new 1:250,000 scale geological map of the Louisville and Monowai segments has been constructed as a framework for a quantitative analysis of arc volcanism and the eruptive history of these segments. Two types of volcanoes dominate the arc front: deep caldera systems (collapse structures formed due to the evacuation of magma) within the arc rifts, and smaller volcanic cones between the rifts. The cone volcanoes tend to have small summit craters (
