Download or read book Characterisation of Mafic Crustal Xenoliths from the Wyoming Craton Montana USA Using Accessory Mineral Geochronology and Geochemistry with Implications for Lower Crustal Evolution written by Yashirvad Thakurdin and published by . This book was released on 2019 with total page 294 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book LA ICP MS Zircon Geochronology of Granulite Xenoliths from the Geronimo Volcanic Field SE Arizona written by Mikaela Alaine Rader and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Lower crustal granulite xenoliths entrained in alkaline basalts from the Geronimo Volcanic Field (GVF), SE Arizona, provide constraints on composition, structure, and age of the lower crust in the southern Basin and Range. The GVF is located in the Mazatzal Province, accreted to the southern margin of Laurentia at ~1.69-1.65 Ga. Previous work conducted in this area provided information on the petrology, geochemistry and geothermometry for the xenolith suite, but age constraints of the xenoliths were limited to Nd model ages, making it difficult to place the evolution of the lower crust in the broader context of the geologic history of the region. This project uses zircon U-Pb geochronology and Hf-isotope analysis to determine the age of formation of GVF lower crust, as well as provide evidence for subsequent tectonic events that impacted its composition. Samples for this suite range in composition from mafic meta-cumulates (plg + cpx ± opx ± ol ± sp) to metadiorites and quartzofeldspathic lithologies (plg + kspar + cpx + ox ± qtz ± opx). GVF xenoliths analyzed for U-Pb geochronology present three distinct zircon age populations at ~1.63-1.65 Ga, ~1.48-1.42 Ga, and ~76-2 Ma, with the majority of young ages concentrated between 35-25 Ma. Zircon U-Pb ages for quartzofeldspathic lithologies present evidence of an event at ~1.65 Ga, suggesting an age of formation consistent with the age of the Mazatzal terrane. However, one quartzofeldspathic zircon core was dated at 2.38 Ga, suggesting the presence of an older component during formation of the Mazatzal crust, possibly originating as cratonic Laurentian sediment. Two quartzofeldspathic xenoliths (MR-GN21-39 and MR-GN21-53) contain zircon cores with discordant U-Pb ages that trend toward ~1.48-1.42 Ga, suggesting modification of the Mazatzal terrane beginning at ~1.48 Ga, the onset of the Picuris Orogeny and widespread 1.48-1.35 Ga plutonism in the southwestern US. These same quartzofeldspathic samples present young ages ranging from ~50-15 Ma, suggesting later alteration of the Proterozoic terrane by Tertiary magmatism associated with Farallon slab subduction. Metadiorites, which were previously inferred to be ~ 1.4 Ga on the basis of whole rock Nd model ages, yielded zircon U-Pb ages ranging from ~76 to 2 Ma, suggesting an origin through thermal resetting of zircons in older Paleoproterozoic crust or addition of new juvenile melts that assimilated Paleoproterozoic crust during magmatic underplating in the Cenozoic. Zircon Hf isotope data from both quartzofeldspathic and metadiorite lithologies are consistent with mantle separation at 2.4 Ga, following an intermediate (176Lu/177Hf = 0.018) crustal isotope evolution path. The existence of positive [epsilon]Hf(t) values in Mesoproterozoic zircon cores of some quartzofeldspathic xenoliths suggest reworking of this older Paleoproterozoic crust sometime between the time of Mazatzal formation and the 1.4 Ga Picuris orogeny and/or the widespread A-type granite event that also occurred across Laurentia at about this time. Eocene to Oligocene age zircons have [epsilon]Hf(t) values that range from -17 to 0, suggesting significant lower crustal modification during Farallon slab subduction.
Download or read book Lower Crustal Xenoliths of the Southern Sierra Nevada A Major Element and Geochronological Investigation written by Adrienne Grant and published by . This book was released on 2016 with total page 45 pages. Available in PDF, EPUB and Kindle. Book excerpt: The continental crust is a chemically distinct geochemical reservoir of the bulk silicate Earth that has formed near continuously over the last 4 billion years and is preserved by its intrinsic buoyancy relative to its oceanic counterpart. Rare earth element patterns imply that continental crust is formed at subduction zone settings and yet the primary melts produced by flux melting of the mantle here are basaltic in composition. An additional process is necessary to differentiate these melts to the Si-rich character of continental crust. The models proposed for differentiation includes fractional crystallization and partial melt extraction, which differ greatly in the resulting lower crustal compositions and the timing of formation relative to Si-rich melts. Here we propose that the investigation of the lower crust composition and timing provides one way to distinguish between these two mechanisms. A study was undertaken to characterize lower crustal xenoliths that are inferred to be related to granitoid plutons from the Southern Sierra Nevadas; the Dinkey Creek and Red Lake granodiorites specifically. Thirteen lower to mid-crustal xenoliths were analyzed for major element chemistry and U-Pb geochronology. We suggest that the broad range in chemistry seen in these lower crustal xenoliths can only be derived by the multiple steps and continuous evolution of fractional crystallization. The ages of these xenoliths record magmatism contemporaneous with the upper crustal granitoid plutons. The mafic lower crustal rocks yield zircon U-Pb dates that are younger than their upper felsic counterparts. This is interpreted to reflect a difference in temperature and crystallization sequence anticipated for mafic and felsic bodies. A summary is developed for the genesis of these plutons and their corresponding mafic cumulate, leading to the generation of crust matching current bulk continental crust estimates.
Download or read book Mantle Xenoliths written by Peter H. Nixon and published by John Wiley & Sons. This book was released on 1987 with total page 892 pages. Available in PDF, EPUB and Kindle. Book excerpt: The eruption of deep-seated xenoliths in basaltic, alnoitic, kimberlitic, etc volcanoes provides the geologist with an important direct means of examining the fragments of the earth's mantle and lower crust.
Download or read book Layered Intrusions written by Bernard Charlier and published by Springer. This book was released on 2015-05-18 with total page 749 pages. Available in PDF, EPUB and Kindle. Book excerpt: This edited work contains the most recent advances related to the study of layered intrusions and cumulate rocks formation. The first part of this book presents reviews and new views of processes producing the textural, mineralogical and geochemical characteristics of layered igneous rocks. The second part summarizes progress in the study of selected layered intrusions and their ore deposits from different parts of the world including Canada, Southwest China, Greenland and South Africa. Thirty experts have contributed to this update on recent research on Layered Intrusions. This highly informative book will provide insight for researchers with an interest in geology, igneous petrology, geochemistry and mineral resources.
Download or read book Crustal Xenoliths from Potrillo Maar written by Indrani Chattopadhyay and published by . This book was released on 2003 with total page 292 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Lutetium hafnium Geochronology and the Ages of Lower Crustal Xenoliths from Kilbourne Hole New Mexico written by Erik E. Scherer and published by . This book was released on 1999 with total page 312 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Petrology of Mafic Granulite Xenoliths Across the Cheyenne Belt Colorado and Wyoming written by Liane M. Stevens and published by . This book was released on 2002 with total page 240 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Geochemistry and Petrography of Crustal Xenoliths from La Olivina Mexico written by James V. Robinson and published by . This book was released on 1988 with total page 234 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Age Composition and Thermal History of Lower Crustal Xenoliths from Artemisia Ekati and Munn Lake Kimberlites of the Slave Craton written by Shauna Marie Coombs and published by . This book was released on 2015 with total page 149 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this study we present data from three lower crustal xenoliths suites collected in a northeast to southwest transect across the Slave craton. The samples are from the Artemisia kimberlite, located near the Coronation diamond district of the northwestern Slave (Nunavut), the Ekati kimberlite from the central Slave (NWT) and the Munn Lake kimberlite of the southeastern Slave (NWT). Samples from the Artemisia Suite have a range of bulk composition but the majority are granitic to semi-pelitic in composition and comprise Garnet + Plagioclase + Quartz + Rutile ± K-feldspar ± Biotite and significant amounts of retrograde hydrous minerals that likely pseudomorph orthopyroxene. As well, there are accessory grains of zircon and monazite. The garnet in these samples is characterized by relatively low grossular contents. In contrast to the Artemisia xenoliths, the Ekati and Munn Lake samples are garnet-bearing mafic granulites with a primary mineralogy of Garnet + Clinopyroxene + Plagioclase ±Quartz ± Orthopyroxene ± Amphibole ± Rutile ± Ilmenite. Metamorphic conditions of the lower crust as indicated by mineral equilibria are in the 9-12 kbar range of pressures with temperatures of at least 750-800°C. In the northern Slave, Neoarchean metamorphic events are recorded at 2624±11 Ma and 2520 Ma and Paleoproterozoic metamorphic events are recorded at 2415 Ma, 2150 Ma, and 2050 Ma and weakly at 2010 Ma. The ages observed in the Artemisia suite may be showing events not seen on the surface and there is a possible correlation with rocks of the Hottah terrane or mafic dike swarms that affected the Slave craton between 2200 and 2000 Ma. Still younger Paleoproterozoic ages of 1826-1868 Ma may be related to the Wopmay orogen. The Artemisia, Ekati and Munn Lake xenolith suites investigated in this study illustrates the complexity of unravelling the history of the lower crust.
Download or read book Toward an Improved Understanding of Intraplate Uplift and Volcanism Geochronology and Geochemistry of Intraplate Volcanic Rocks and Lower Crustal Xenoliths written by Leonard D. Ancuta and published by . This book was released on 2017 with total page 207 pages. Available in PDF, EPUB and Kindle. Book excerpt: The origin of diffuse intraplate volcanism and 4000 m high topography of the Hangay Mountains in central Mongolia is enigmatic, as it is not explained by or predicted by traditional plate tectonic models. Chapter One presents new whole-rock 40Ar/39Ar ages that range from Holocene to 30 Ma for the Cenozoic volcanic rocks in central Mongolia. The total volume of the Cenozoic volcanic rocks is approximately 1540 km3, but prior to erosion, the volume may have been as high as 2900 km3. Volcanism began to increase gradually in the early Miocene and peaked in the middle Miocene, with a gradual decrease in volume through the Holocene. The low total volumes and the lack of an age progressive hot-spot track rule out the presence of a mantle plume. The long-term gradual increase and subsequent decrease in volcanic output may also rule out delamination. Chapter Two presents the results of a geochemical study to understand the source of the volcanic rocks. Isotopic compositions of the volcanic rocks fall between prevalent mantle (PREMA) and enriched mantle (EM1) and are similar to other Cenozoic basalts from east Asia, though markedly different from the depleted MORB mantle (DMM) isotopic signature of the lithospheric mantle in Mongolia, suggesting the volcanic rocks must be derived from a sub-lithospheric source. A mantle upwelling beneath the region is likely, though the specific cause can not be identified by geochemistry and geochronology alone. In Chapter Three, two-pyroxene granulite lower crustal xenoliths brought to the surface by the Cenozoic volcanism were studied using U-Pb geochronology and geochemistry. U-Pb geochronology indicates the lower crust in central Mongolia began to form by at latest the Permo-Triassic, likely during the formation of the Central Asian Orogenic Belt (CAOB), which is consistent with arc-like geochemical signatures. Recent seismology studies indicate that the high elevations of the Hangay region could be isostatically supported by a thick crust. My new data suggests the lower crust, and by inference the high topography of the Hangay, formed in the Late Paleozoic to Early Mesozoic during the formation of the CAOB, which is significantly older than any other previous estimates.
Download or read book Petrology and Geochemistry of Upper Mantle and Lower Crustal Xenoliths from Thailand written by Prinya Promprated and published by . This book was released on 2001 with total page 302 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Petrographic Geochemical and Age Characterisation of Crustal Xenoliths from Coliban Dam Central Victoria written by Shelley Allchurch and published by . This book was released on 2008 with total page 241 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Composition and Evolution of the Lower Crust Central Montana written by David Joswiak and published by . This book was released on 1992 with total page 308 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Belt Basin Window to Mesoproterozoic Earth written by John S. MacLean and published by Geological Society of America. This book was released on 2016-06-01 with total page 400 pages. Available in PDF, EPUB and Kindle. Book excerpt: With its thickness of more than 15 km of strata, covering some 200,000 km2, the Belt basin displays one of the planet's largest, best-exposed, most accessible, and best-preserved sequences of Mesoproterozoic sedimentary and igneous rocks. This volume focuses on research into this world-class province; kindles ideas about this critical era of Earth evolution; and covers aspects of the basin from its paleontology, mineralogy, sedimentology, and stratigraphy to its magmatism, ore deposits, geophysics, and structural geology.
Download or read book Detailed Study of Mafic Lower Crustal Xenoliths from the Bakony Balaton Highland Volcanic Field written by Dégi Júlia and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Geochemistry of Lower crustal Xenoliths from the Royal Society Range of the Transantarctic Mountains Antarctica written by Jane Matheney and published by . This book was released on 1989 with total page 318 pages. Available in PDF, EPUB and Kindle. Book excerpt:
