Architecture And Evolution Of The Crust During Continental Arc Magmatism
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Architecture And Evolution Of The Crust During Continental Arc Magmatism
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Author : Glenn J. Woodsworth
language : en
Publisher: Geological Society of America
Release Date : 2020-07-06
Architecture And Evolution Of The Crust During Continental Arc Magmatism written by Glenn J. Woodsworth and has been published by Geological Society of America this book supported file pdf, txt, epub, kindle and other format this book has been release on 2020-07-06 with Science categories.
Architecture And Evolution Of The Crust During Continental Arc Magmatism
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Author : Glenn James Woodsworth
language : en
Publisher:
Release Date : 2020
Architecture And Evolution Of The Crust During Continental Arc Magmatism written by Glenn James Woodsworth and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2020 with Geology categories.
Originally prepared for the GSA Thompson Field Forum that ran from Terrace to Prince Rupert, British Columbia, this guide describes the geology along the Skeena River transect of the Coast Mountains batholith, the largest Cordilleran batholith of western North America and one of the largest continental-margin batholiths in the world. The last guide to this area was published in 1983 and this new volume is the only modern overview of the last decades of work. The authors use the transect as a basis to examine the growth of the Coast Mountains batholith as a whole, emphasizing commonalities and variations with the batholith and how these traits may reflect magmatic processes that create convergent-margin batholiths.
Crustal Architecture And Magma Dynamics In A Large Continental Magmatic System
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Author : Dale H. Burns
language : en
Publisher:
Release Date : 2014
Crustal Architecture And Magma Dynamics In A Large Continental Magmatic System written by Dale H. Burns and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2014 with Ignimbrite categories.
The ~1 Myr history of the Purico-Chascon volcanic complex (PCVC) records significant changes in the production and storage of magmas in the crust. At ~1 Ma activity at the PCVC initiated with the eruption of a large 80-100 km3 crystal-rich dacite ignimbrite with restricted whole rock 87Sr/86Sr isotope ratios between 0.7085-0.7090. In-situ analyses of plagioclase from the Purico ignimbrite have 87Sr/86Sr=0.7087-0.7090. The dacite magma accumulated and evolved at relatively low temperatures around 800-850 °C in the upper crust at 4-8 km depth. Minor andesite and rhyolite pumice late in the sequence have similar restricted whole rock 87Sr/86Sr=0.7089-0.7091. The radiogenic isotopes of this 0.98 Ma activity are consistent with all these compositions resulting from 50 to 70% crustal assimilation by parental Central Andean "baseline" magmas at depths between 15-30 km. The final eruptions at the PCVC occurred 0.18 Ma producing three small 5 km3 crystal-rich dacite lava domes with whole rock 87Sr/86Sr ratios 0.7075 to 0.7081 containing abundant basaltic-andesite enclaves with whole rock 87Sr/86Sr ratios of 0.7057- 0.7061. Plagioclase and amphibole from samples from the largest of these domes, Cerro Chascon, record two distinct magmatic environments; an upper crustal environment identical to the Purico ignimbrite and a second deeper, ~15-20 km depth, higher temperature (~922-1001 °C) environment consistent with conditions recorded in the basaltic andesite enclaves. Accordingly, plagioclase cores in the host dacite lava and enclaves have enriched in-situ 87Sr/86Sr isotopic compositions of 0.7083 to 0.7095 while plagioclase rims and microphenocrysts in the enclaves have 87Sr/86Sr isotope ratios from 0.7057 to 0.7065 and 0.7062 to 0.7064 respectively. Lavas from Cerro Chascon also contain abundant Fo82 olivine with spinel and basaltic melt inclusions that crystallized in a deep crustal environment (1250 °C) consistent with a lower crustal MASH zone. The high baseline isotopic ratios observed in bulk rock and plagioclase crystals from Cerro Chascon (0.7057-0.7065) are consistent with MASH processes. The evolution of the PCVC is a microcosm of the Andean arc in this region where, from 10 - 1 Ma, dominantly dacitic upper crustal magmatism of the Altiplano-Puna Volcanic Complex ignimbrite flare-up persisted until ~1 Ma, when smaller volume, more heterogeneous and less isotopically enriched basaltic andesite to dacite composite volcanoes signal a return to steady state arc volcanism. I suggest that the PCVC captures the transition of the Andean arc from flare-up to steady state. The temporal trend at the PCVC is consistent with a waning thermal flux. High magmatic fluxes during the flare-up would have resulted in elevated geothermal gradients and efficient crustal processing leading to a dominantly dacitic upper crust (0 to 35 km) that fed the large volume Purico ignimbrite. As magmatic flux and thermal energy wanes, crustal isotherms relax resulting in greater thermal contrast between parental magmas, crust and remnant upper crustal dacite magma. This manifests in more heterogeneity and the survival of less isotopically enriched magmas in the upper crust. These arc scale magma dynamics are recorded even at the intra-crystalline scale. Individual crystals from Cerro Chascon also record vital information on the crystallization and evolution of mantle-derived magmas in continental magmatic arcs. Fo2 olivine, olivine hosted spinel, and basaltic melt inclusions record the crystallization of olivine at1250 °C in conditions consistent with a lower crustal (~70 km depth) MASH zone. Another significant crystallization event appears to have occurred at ~20 km depth, characterized by the crystallization of high An plagioclase (An--24) at ~1100-1050 °C followed by high-Al amphibole (~12-15 wt.% Al2O3) at ~1000-950 °C. The appearance of amphibole on the liquidus appears to have resulted from a nearly 2-fold increase in melt water content following ~45% crystallization of high An plagioclase. Following this extensive crystallization the highly crystalline mafic magma ascended into the upper crust and interacted with the remnant crystal mush from the Purico ignimbrite magma reservoir. Low An plagioclase (An3955), low Al amphibole (~6-9 wt.% Al2O3), sanidine, and biotite retain the chemical composition of the Purico ignimbrite magma, whereas, olivine, high An plagioclase, and high Al amphibole record the mafic recharge magma. The textures and compositions observed in Cerro Chascon are common in both continental and oceanic magmatic arcs worldwide and I propose that multiple crystallization events and upper crustal assimilation are fundamental processes intrinsic to arc magmatism. I have also used in situ 87Sr/86Sr isotope ratios in plagioclase from andesite, dacite, and rhyolite pumice from the ~1 Ma Purico ignimbrite to determine the cause for compositional zoning in the Purico ignimbrite magma reservoir. Andesite pumice contains two texturally, compositionally, and isotopically distinct types of plagioclase, small (500 [micro]m) subhedral to euhedral crystals with high MgO (130-490 ppm) and low 87Sr/86r crystals (0.7076-0.7084) record a hot (900 °C) andesite magma derived from an ~20 km deep magma reservoir. In contrast, the second type of plagioclase in the andesite appear to broken fragments of larger crystals and have significantly lower MgO (90-240 ppm), higher 87Sr/86Sr (0.7096-0.7114), and appears to be derived from the lower temperature (crystallized at ~800-900 °C), upper crustal (10 km) plutonic basement. Dacite pumice also contains two texturally and compositionally distinct types of plagioclase. However, both types have very restricted MgO (b.d.l.-200 ppm) and 87Sr/86Sr (0.7085-0.7095) ratios and appear to have grown at ~850°C. These crystals are also significantly larger (1000 [micro]m) than plagioclase from the andesite pumice and have clear euhedral rims. Rhyolite pumice from the Purico ignimbrite also contains distinct types of plagioclase. Both types of plagioclase are similar in size (
Evolution Of The Continental Crust And Significance Of The Zircon Record A Case Study From The French Massif Central
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Author : Simon Couzinié
language : en
Publisher:
Release Date : 2017
Evolution Of The Continental Crust And Significance Of The Zircon Record A Case Study From The French Massif Central written by Simon Couzinié and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017 with categories.
The formation of the continental crust is a major consequence of Earth differentiation. Understanding how the crust formed and evolved through time is paramount to locate the vast mineral deposits hosted therein and address its influence on the global climate, ultimately affecting the development of terrestrial life. Recent advances on the topic of continental crust evolution benefited from improvements of analytical techniques enabling in situ measurements of U-Pb- Hf-O isotope compositions in zircon, a widespread accessory mineral of continental igneous rocks. The time constrains derived from the U-Pb chronometer coupled with the petrogenetic information retrieved from Hf-O isotope signatures are currently used to unravel the diversity and succession of magmatic events affecting the continental crust at the regional and global scales. This study reconstructs the evolutionary path followed by the crust segment today exposed in the eastern part of the French Massif Central (FMC), a portion of the Variscan belt of Western Europe, with the aim to investigate the potential flaws of the zircon record of crust evolution. In this scope, the origin and geodynamic significance of the constituent FMC lithological units are tackled by combining conventional petrological observations with zircon U-Pb-Hf-O isotope data. The results obtained following this integrated approach are then confronted to the conclusions that would have been drawn solely from zircon isotopic signatures, taken out of their petrological context, as is commonly performed in studies investigating crust evolution. The oldest rocks of the FMC correspond to Ediacaran (590_550 Ma) meta-sediments deposited in back-arc basins along the northern Gondwana margin. Such basins were fed by a mixed detritus originating from the adjacent Cadomian magmatic arc and a distal Gondwana source, presumably the Sahara Metacraton. Partial melting of these meta-sediments at the Ediacaran/Cambrian boundary led to voluminous S-type granitic magmatism, pinpointing a first major crust reworking event in the FMC. The origin of anatexis likely stems from the transient thickening of the hot, back-arc crust caused by the flattening of the Cadomian subduction. Subordinate melting of the depleted backarc mantle at that time is also documented. During the Lower Paleozoic, rifting of the northern Gondwana provoked coeval crust and (limited) mantle melting. Mantle-derived igneous rocks show markedly diverse trace element and isotopic signatures, consistent with a very heterogeneous mantle source pervasively modi_ed by the Cadomian subduction. Finally, the Variscan collision resulted in crustal melting as evidenced by the emplacement of S-type granites and the formation of migmatite domes, the spatial distribution of which being partly controlled by the crustal architecture inherited from pre-orogenic events. Synchronous intrusion of mafic mantle-derived magmas and their differentiates testify for Variscan post-collisional new continental crust production in the FMC. Two major inconsistencies exist between these results and the zircon record. First, zircon Hf model ages would point to substantial Mesoproterozoic crust formation in the FMC whereas more than 60% of the crust is actually Neoproterozoic in age. Second, new additions to the continental crust volume during the Variscan orogeny are not recorded even though 5 to 10% of the exposed crust formed at that time. The origin of both discrepancies inherently lies in the mixed isotopic signature carried by many zircon grains. Such equivocal information can only be detected when additional petrological constrains on the zircon host rocks are available and provide guidance in interpreting the zircon record of crust evolution.
Himalaya Dynamics Of A Giant Tectonic Units And Structure Of The Himalaya
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Author : Rodolphe Cattin
language : en
Publisher: John Wiley & Sons
Release Date : 2023-08-29
Himalaya Dynamics Of A Giant Tectonic Units And Structure Of The Himalaya written by Rodolphe Cattin and has been published by John Wiley & Sons this book supported file pdf, txt, epub, kindle and other format this book has been release on 2023-08-29 with Science categories.
Magma Dynamics And Evolution In Continental Arcs
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Author : Stephanie B. Grocke
language : en
Publisher:
Release Date : 2014
Magma Dynamics And Evolution In Continental Arcs written by Stephanie B. Grocke and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2014 with Magmas categories.
Constraining the magma evolution and dynamics that lead to the eruption of large volume continental arc systems is fundamental to our understanding of continental crust formation. An investigation into the magmagenesis that results in the formation of the Central Volcanic Zone (CVZ) in the Andes of South America, situated atop overthickened continental crust (80 km thick), provides insights into large volume silicic magma reservoirs and how they evolve prior to their potentially catastrophic explosive eruption on the Earth's surface. A focused case study of the Cerro Guacha Caldera Complex (CGCC), a nested volcanic system in the Altiplano-Puna Volcanic Complex of SW Bolivia, puts constraints on the progressive stages of development of the magmatic underpinnings of the caldera complex. Whole rock data, in conjunction with matrix glass, mineral compositions and melt inclusions, are used to infer processes that gave rise to the formation of the Guacha II Caldera, the younger of two main collapse features, formed from the supereruption of the Tara Ignimbrite (800 km3 DRE) at 3.49 ± 0.01 Ma. The eruptive history of the Guacha II Caldera from pre-caldera to post-caldera is fully represented, allowing magma dynamics associated with a complete caldera cycle, from pre-climactic (catastrophic caldera-forming) magma accumulation through to post-climactic effusions that are part of the resurgent history of the caldera, to be examined. Analysis of the high-K, calcalkaline suite of andesite to high Si-rhyolite Tara pyroclastic deposits provides insights into the storage conditions and magma dynamics leading up to a supervolcanic eruption. The Tara eruptive products define a liquid line of descent from the basal andesite lava (62 wt % SiO2) to the high-silica rhyolite post-collapse Chajnantor Dome lava (78 wt.% SiO2), with major and trace element trends consistent with fractionation of quartz, plagioclase, orthopyroxene, hornblende, sanidine, biotite, and Fe-Ti oxides. Isotope ratios span a significant range in 87Sr/86Sr (0.709 to 0.713) and a relatively narrow range in 143Nd/144Nd (0.512179 to 0.512297) and [delta]18O[subscript (qtz)] (+8.68 to +8.43[per mil]). These data require AFC processes to explain both the isotope and trace element compositions in the Tara magmas. Geothermobarometry reveals pre-eruptive temperatures (~800 - 950 °C), pressures (~200 MPa), and H2O contents (~5 wt%) that suggest storage of a large-volume rhyodacite magma reservoir between 5 and 9 km depth in the upper crust. Analyses of quartz-hosted melt inclusions from pumices in the climactic plinian and ignimbrite phase of eruption reveal that pre-eruptive H2O contents in the plinian pumice overlap with those in the ignimbrite pumice (2.2 to 6.0 and 2.1 to 5.4 wt.% H2O, respectively). The ignimbrite magma, however, contains higher CO2 (630 versus
Crustal Architecture And Evolution Of The Himalaya Karakoram Tibet Orogen
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Author : R. Sharma
language : en
Publisher: Geological Society of London
Release Date : 2019-09-27
Crustal Architecture And Evolution Of The Himalaya Karakoram Tibet Orogen written by R. Sharma and has been published by Geological Society of London this book supported file pdf, txt, epub, kindle and other format this book has been release on 2019-09-27 with Science categories.
This volume comprises 17 contributions that address the architecture and geodynamic evolution of the Himalaya–Karakoram–Tibet (HKT) system, covering wide aspects, from the active seismicity of the present day to the remnants of the Proterozoic orogen. The articles investigate the HKT system at different scales, blending field research with laboratory studies. The role of various lithospheric components and their inheritance in the geodynamic and magmatic evolution of the HKT system through time, and their links to global geological events, are studied in the field. The laboratory research focuses on the (sub-)micrometre scale, detailing micro-structural geology, crystal chemistry, geochronology, and the study of circulating fluids, their preservation (trapped in fluid inclusions) and their evolution, distribution, migration and interaction with the solid host. An orogen over 2000 km long can be understood only if the processes at the nanometre and micrometre scales are taken into account. The contributions in this volume successfully combine these scales to enhance our understanding of the HKT system.
The Role Of Volatiles In The Genesis Evolution And Eruption Of Arc Magmas
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Author : G.F. Zellmer
language : en
Publisher: Geological Society of London
Release Date : 2015-03-17
The Role Of Volatiles In The Genesis Evolution And Eruption Of Arc Magmas written by G.F. Zellmer and has been published by Geological Society of London this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015-03-17 with Science categories.
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.
Precambrian Geology
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Author : Alan M. Goodwin
language : en
Publisher: Elsevier
Release Date : 2016-02-06
Precambrian Geology written by Alan M. Goodwin and has been published by Elsevier this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016-02-06 with Science categories.
The main goal of this book is to provide a modern comprehensive statement on the Earth's Precambrian crust. It uses geographic and tectonic location, lithostratigraphy, geochronology, and petrogenesis as a basis for considering Precambrian coastal evolution--including the role of plate tectonics. Detailed consideration is given to the endogenic and exogenic processes which formed the continental crust and also to its subsequent secular evolution across Precambrian time**An essential reference volume for every Precambrian geologist.
Crustal Magmatic System Evolution
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Author : Matteo Masotta
language : en
Publisher: John Wiley & Sons
Release Date : 2021-07-07
Crustal Magmatic System Evolution written by Matteo Masotta and has been published by John Wiley & Sons this book supported file pdf, txt, epub, kindle and other format this book has been release on 2021-07-07 with Science categories.
A comprehensive picture of the architecture of crustal magmatic systems The composition of igneous rocks – their minerals, melts, and fluids – reveals the physical and chemical conditions under which magmas form, evolve, interact, and move from the Earth’s mantle through the crust. These magma dynamics affect processes on the surface including crustal growth and eruptive behaviour of volcanoes. Crustal Magmatic System Evolution: Anatomy, Architecture, and Physico-Chemical Processes uses analytical, experimental, and numerical approaches to explore the diversity of crustal processes from magma differentiation and assimilation to eruption at the surface. Volume highlights include: Physical and chemical parameterization of crustal magmatic systems Experimental, theoretical and modelling approaches targeting crustal magmatic processes Timescales of crustal magmatic processes, including storage, recharge, and ascent through volcanic conduits The American Geophysical Union promotes discovery in Earth and space science for the benefit of humanity. Its publications disseminate scientific knowledge and provide resources for researchers, students, and professionals. Find out more about this book in a Q&A with the Editors.