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Статті в журналах з теми "Tholeiitic volcanics"
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Melling, David R., Charles E. Blackburn, David H. Watkinson, and Jack R. Parker. "Geological setting of gold, western Wabigoon Subprovince, Canadian Shield: exploration targets in mixed volcanic successions." Canadian Journal of Earth Sciences 25, no. 12 (December 1, 1988): 2075–88. http://dx.doi.org/10.1139/e88-192.
Повний текст джерелаАнотація:
The Archean volcanic rocks in the Cameron–Rowan lakes area may be divided into three distinct successions based on field mapping, petrographic studies, and lithogeochemical characteristics. The lowermost Rowan Lake Volcanics are tholeiitic pillowed basalts. These rocks are unconformably overlain by the Cameron Lake Volcanics, a mixed succession of tholeiitic massive and pillowed basalts and intermediate to felsic volcaniclastic rocks. The Brooks Lake Volcanics consist of tholeiitic basalts and represent the youngest volcanic rocks at the top of the preserved succession.Most of the gold concentrations in the Cameron–Rowan lakes area are confined to the mixed Cameron Lake Volcanics. The majority of these, including the Cameron Lake deposit, occur within shear zones near lithologic contacts. In the Eagle–Wabigoon and Manitou lakes areas there are similar stratigraphic subdivisions of the supracrustal rocks and many of the gold concentrations also occur in deformation zones within the mixed volcanic successions. The contrasting competencies among the basalts, the intermediate to felsic volcaniclastic rocks, and the intrusive rocks, which are characteristic of the mixed volcanic successions, localized stress during deformation, forming shear zones into which gold-bearing fluids gained access. The potential for successfully delineating economic gold concentrations appears greatest in the mixed volcanic successions within these areas and elsewhere in the western Wabigoon Subprovince of the Canadian Shield.
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Monjoie, Philippe, Henriette Lapierre, Artan Tashko, Georges H. Mascle, Aline Dechamp, Bardhyl Muceku, and Pierre Brunet. "Nature and origin of the Triassic volcanism in Albania and Othrys: a key to understanding the Neotethys opening?" Bulletin de la Société Géologique de France 179, no. 4 (July 1, 2008): 411–25. http://dx.doi.org/10.2113/gssgfbull.179.4.411.
Повний текст джерелаАнотація:
AbstractTriassic volcanic rocks, stratigraphically associated with pelagic or reef limestones, are tectonically juxtaposed with Mesozoic ophiolites in the Tethyan realm. From the central (Dinarides, Hellenides) and eastern Mediterranean (Antalya, Troodos, Baër Bassit) to the Semail nappes (Oman), they occur either associated to the tectonic sole of the ophiolitic nappes or as a distinct tectonic pile intercalated between the ophiolites and other underthrust units. In the Dinaro-Hellenic belt, the Pelagonian units represent the lower plate, which is underthrust beneath the ophiolites. Middle to Late Triassic volcanic sequences are interpreted as the eastern flank of the Pelagonian platform and are therefore considered as a distal, deep-water part of the Pelagonian margin.The Triassic volcanics from Albania and Othrys are made up of basaltic pillowed and massive flows, associated locally with dolerites and trachytes. New elemental, Nd and Pb isotopic data allow to recognize four types of volcanic suites: (1) intra-oceanic alkaline and tholeiitic basalts, (2) intra-oceanic arc-tholeiites, (3) back-arc basin basalts, (4) calc-alkaline mafic to felsic rocks. Nd and Pb isotopic initial ratios suggest that the within-plate volcanic rocks were derived from an enriched oceanic island basalt type mantle source, devoid of any continental crustal component. The lower εNd value of the trachyte could be due to assimilation of oceanic altered crust or sediments in a shallow magma chamber. Island arc tholeiites and back-arc basin basalts have a similar wide range of εNd. The absence of Nb negative anomalies in the back-arc basin basalts suggests that the basin floored by these basalts was wide and mature. The high Th contents of the island arc tholeiites suggest that the arc volcanoes were located not far away from the continental margin.Albania and Othrys volcanics contrast with the Late Triassic volcanism from eastern Mediterranean (SW Cyprus, SW Turkey), which displays solely features of oceanic within plate suites. The presence of back-arc basin basalts associated with arc-related volcanics in Central Mediterranean indicates that they were close to a still active subduction during the Upper Triassic, while back-arc basins developed, associated with within-plate volcanism, leading to the NeoTethys opening.
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Tripathi, C. "Volcanism in Gondwanas." Journal of Palaeosciences 36 (December 31, 1987): 285–89. http://dx.doi.org/10.54991/jop.1987.1587.
Повний текст джерелаАнотація:
In India the Lower Permian event is marked by a major volcanic episode in the Himalayan belt and rift faulting in the Peninsula which gave rise to various Gondwana basins. The Lower Cretaceous major volcanic episode represented by the Rajmahal Trap represents the termination of Gondwana sedimentation. Lower Permian volcanism is represented by the Panjal Volcanics in Kashmir Basin and its equivalent, the Volcanics in Spiti-Zanskar Basin and Rotung Volcanics (Abor Volcanics) in Arunachal Pradesh. In Karakarom Basin of Ladakh, volcanism is associated with Changtash and Aqtash formations of Permian age.
The Agglomeratic Slates in Kashmir are supposed to have originated as explosive volcanism in the form of pyroclastic which was followed later by flows of the Panjal Volcanics represented by subaqueous and subaerial tholeiitic basalt with occasional basaltic, andesitic and rhyolitic volcanics. The Agglomeratic slates are divided into two divisions, the Lower Diamicites and the Upper Pyroclastic. At the base of the Pyroclastic division and at the top of the Diamictite division, we get Eurydesma-Deltopecten Fauna of Lower Permian age. It is thus established that volcanism in Kashmir, Spiti-Zanskar and Ladakh is restricted to Lower Permian only. The sills and dykes associated with the underlying sequence in Syringothyris Limestone and Fenestella Shale in Kashmir, in Lipak and Po Formations in Spiti are related to this volcanism.
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Smith, Alan D. "Geochemistry and tectonic setting of volcanics from the Anyox mining camp, British Columbia." Canadian Journal of Earth Sciences 30, no. 1 (January 1, 1993): 48–59. http://dx.doi.org/10.1139/e93-005.
Повний текст джерелаАнотація:
Volcanogenic massive sulphide deposits at Anyox in the Tracy Arm terrane of the Canadian Cordillera are associated with a sequence of tholeiitic basalts with minor intercalated basaltic andesite tuffs and siliceous sediments. Sm–Nd and Pb–Pb systematics indicate an Early to Middle Jurassic age. The tholeiites are characterized by normal mid-ocean-ridge basalt to weak island-arc tholeiite trace element signatures with slight enrichment in large-ion lithophile elements and depletion in high-field-strength elements, high 207Pb/204Pb, and εNd(170 Ma) values of +8.2 to +8.4. The mineralized sequence is conformably overlain by argillaceous sediments and minor limestones. These features, combined with the location of the strata and similarities with the Spider Peak Formation of the Methow terrane, indicate an origin in a narrowing marginal basin that once separated superterranes I and II.
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Rouer, O., H. Lapierre, C. Coulon, and A. Michard. "New petrological and geochemical data on mid-Paleozoic island-arc volcanics of northern Sierra Nevada, California: evidence for a continent-based island arc." Canadian Journal of Earth Sciences 26, no. 12 (December 1, 1989): 2465–78. http://dx.doi.org/10.1139/e89-210.
Повний текст джерелаАнотація:
The mid-Paleozoic volcanics of northern Sierra Nevada consist of the Sierra Buttes rhyolites, the Taylor basalts and andesites, and the Keddie Ridge basalt–latite–rhyolite suite. The Sierra Buttes calc-alkaline rhyolites display strong light rare-earth element enrichment and negative εNd values. The Taylor basalts and andesites in the northern Hough and Genesee blocks exhibit calc-alkaline affinities (REE rare-earth element patterns highly enriched in LREE), whereas in the southern Hough block they are tholeiitic (flat rare-earth element patterns). The abundance of silicic lavas, the low εNd values of both the Sierra Buttes and Taylor volcanics and the δ18O values of the Sierra Buttes rhyolite and Bowman Lake trondjhemite provide evidence that the northern Sierra Nevada island arc was continent based. The Keddie Ridge differentiated volcanics, characterized by high Zr, Y, Nb, K, and light rare-earth elements, are geochemically similar to a shoshonite suite. Their eruption at the end of the mid-Paleozoic volcanic episode suggests a reversal of subduction, uplift, and block faulting in the island arc.The mid-Paleozoic volcanics of the northern Sierra Nevada are thought to represent the remnant of a mature island arc because calc-alkaline rocks predominate over tholeiitic ones, the lavas display a K enrichment with time, and the volcanics are evolved in their isotopes, compared with rocks erupted in young or primitive island arcs.
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Ludden, John, Claude Hubert, and Clement Gariépy. "The tectonic evolution of the Abitibi greenstone belt of Canada." Geological Magazine 123, no. 2 (March 1986): 153–66. http://dx.doi.org/10.1017/s0016756800029800.
Повний текст джерелаАнотація:
AbstractBased on structural, geochemical, sedimentological and geochronological studies, we have formulated a model for the evolution of the late Archaean Abitibi greenstone belt of the Superior Province of Canada. The southern volcanic zone (SVZ) of the belt is dominated by komatiitic to tholeiitic volcanic plateaux and large, bimodal, mafic-felsic volcanic centres. These volcanic rocks were erupted between approximately 2710 Ma and 2700 Ma in a series of rift basins formed as a result of wrench-fault tectonics.The SVZ superimposes an older volcanic terrane which is characterized in the northern volcanic zone (NVZ) of the Abitibi belt and is approximately 2720 Ma or older. The NVZ comprises basaltic to andesitic and dacitic subaqueous massive volcanics which are cored by comagmatic sill complexes and layered mafic-anorthositic plutonic complexes. These volcanics are overlain by felsic pyroclastic rocks that were comagmatic with the emplacement of tonalitic plutons at 2717 ±2 Ma.The tectonic model envisages the SVZ to have formed in a series of rift basins which dissected an earlier formed volcanic arc (the NVZ). Analogous rift environments have been postulated for the Hokuroko basin of Japan, the Taupo volcanic zone of New Zealand and the Sumatra and Nicaragua arcs. The difference between rift related ‘submergent’ volcanism in the SVZ and ‘emergent’ volcanism in the NVZ resulted in the contrasting metallogenic styles, the former being characterized by syngenetic massive sulphide deposits, whilst the latter was dominated by epigenetic ‘porphyry-type’ Cu(Au) deposits.
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Norman, David I., Kent C. Condie, Robert W. Smith, and W. F. Thomann. "Geochemical and Sr and Nd isotopic constraints on the origin of late Proterozoic volcanics and associated tin-bearing granites from the Franklin Mountains, west Texas." Canadian Journal of Earth Sciences 24, no. 4 (April 1, 1987): 830–39. http://dx.doi.org/10.1139/e87-081.
Повний текст джерелаАнотація:
Late Proterozoic volcanic and granitic rocks from the Franklin Mountains in west Texas define a continuous tholeiitic trend from rhyolite (granite) to trachyte with a small compositional gap between trachyte and basalt. Volcanics and granitic rocks have immobile-element geochemical affinities with volcanics from continental-margin-arc systems and associated back-arc basins. Felsic volcanics and granitic rocks appear to have formed by fractional crystallization of basalt during which REE and high-field-strength elements were stabilized as fluoride complexes and concentrated in late or post-magmatic fluids.A Rb–Sr isochron from nonhematized samples (1064 ± 5 Ma, i = 0.7034) falls within the error of reported U–Pb zircon dates and probably dates a period of hydrothermal alteration. εNd values (0.7–2.5 at 1065 Ma) fall below a depleted mantle growth curve and probably reflect contamination of the fractionating magmas with older continental crust. Changes in the isotopic composition of Nd during hydrothermal alteration may also contribute to the spread in εNd values.
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Chandra, Rakesh, Rajeev Upadhyay, and Anshu K. Sinha. "Subduction and collision related magmatism in the Shyok Suture and eastern Karakoram." Journal of Palaeosciences 48, no. (1-3) (December 31, 1999): 183–209. http://dx.doi.org/10.54991/jop.1999.1303.
Повний текст джерелаАнотація:
The Shyok Suture is represented by distinct sets of volcano-plutonic rock assemblages. The high-Mg tholeiitic basalt and calc-alkaline andesites of the Shyok Volcanics have a subduction zone chemical signature. The REE data on tholeiitic basalt suggest a chemical affinity between primitive N-MORB to E-MORB. The calc-alkaline andesites, however, resembles to transitional nature of basalt between E-MORB to OIB. The geochemical data and regional tectonic setting suggest a close similarity between the Shyok Volcanics of northern Ladakh and the Chalt Volcanics of Kohistan.
The mildly deformed trondhjemite-tonalite-granodiorite of the Tirit Granitoids are composite plutons located south of the Shyok Suture melange. These granitoids are subalkaline, I-type and represented by volcanic arc chemical signatures. The regional tectonic setting, the nature of occurrence and the composition of Tirit Granitoids are similar to the plutonic suites of northern Kohistan (Gindai, Matum Das and Nomal plutons).
The eastern Karakoram Batholith is dominated by quartz monzonite-tonalite-granodiorite and granite. The subalkaline to calc-alkaline Karakoram Batholith is constituted by both I-and S-type granitoids with volcanic arc and syn-collision chemical signatures. REE data suggest that the I-type granitoids of eastern Karakoram are calc-alkaline magmatism of a subduction zone environment. In contrast, most of the S-type granitoids are crust-derived peraluminous granitoids. New Rb/Sr isotopic whole rock age data indicates that an S-type intrusive phase was active in the eastern Karakoram region during 83±9 Ma. The syn-collision nature of these granitoids are similar to those of north Sost pluton and Karambar pluton of northern Kohistan.
This indicates that the collision between Kohistan-Ladakh arc and Karakoram block was active during 83±9 Ma.
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Chauvet, François, Henriette Lapierre, Delphine Bosch, Stéphane Guillot, Georges Mascle, Jean-Claude Vannay, Jo Cotten, Pierre Brunet, and Francine Keller. "Geochemistry of the Panjal Traps basalts (NW Himalaya): records of the Pangea Permian break-up." Bulletin de la Société Géologique de France 179, no. 4 (July 1, 2008): 383–95. http://dx.doi.org/10.2113/gssgfbull.179.4.383.
Повний текст джерелаАнотація:
AbstractThe late Lower to Middle Permian Panjal Traps (NW Himalaya, India-Pakistan) represent the greatest magmatic province erupted on the northern Indian platform during the Neotethys opening. New geochemical and isotopic analyses were performed on basalts from the eastern borders of the traps (SE Zanskar-NW Spiti area) in order to characterize this volcanism, to discuss its compositional variations in comparison to Panjal counterparts and its relationships with the opening of Neotethys. Lavas show features of tholeiitic low-Ti (< 1.6%) continental flood basalts with LREE, Th enrichments and Nb-Ta negative anomalies. Trace element ratios combined with εNdi values (−3.6 to +0.9) and high Pb isotopic ratios suggest that these tholeiitic basalts were derived from an OIB-like mantle contaminated at various degrees by a continental crust component. Previous geochemical features are broadly similar to those of the coeval Panjal volcanic sequences identified westwards (Ladakh, Kashmir and Pakistan). Present geochemical constraints obtained for the Panjal Traps basalts suggest they originated from rapid effusion of tholeiitic melts during opening of the Neotethys Ocean. Similar magmatism implying an OIB-type reservoir is contemporaneously recognized on and along the adjacent Arabian platform. Both Indian and Arabian Permian volcanics were emplaced during coeval syn-rift to post rift transition. These Lower to Middle Permian south Neotethyan continental flood magmatism are regarded as associated to a passive rifting. In this scheme, OIB-type isotopic signature would be related either to a melting episode of syn-rift up-welling mantle plumes or to a melting of a regional abnormally hot and enriched mantle.
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Petterson, M. G. "The plutonic crust of Kohistan and volcanic crust of Kohistan–Ladakh, north Pakistan/India: lessons learned for deep and shallow arc processes." Geological Society, London, Special Publications 483, no. 1 (July 30, 2018): 123–64. http://dx.doi.org/10.1144/sp483.4.
Повний текст джерелаАнотація:
AbstractThe Kohistan–Ladakh terrane, northern Pakistan/India, offers a unique insight into whole-arc processes. This research review presents summaries of fundamental crustal genesis and evolution models. Earlier work focused on arc sequence definition. Later work focused on holistic petrogenesis. A new model emerges of an unusually thick (c. 55 km) arc with a c. 30 km-thick batholith. Volatile-rich, hornblende ± garnet ± sediment assimilation-controlled magmatism is predominant. The thick batholith has a complementary mafic–ultramafic residue. Kohistan crustal SiO2 contents are estimated at >56%. The new-Kohistan, silicic-crust model contrasts with previous lower SiO2 estimates (c. 51% SiO2 crust) and modern arcs that imply <35 km crustal thicknesses and arc batholith thicknesses of c. 7 km. A synthetic overview of Kohistan–Ladakh volcanic rocks presents a model of an older, cleaved/deformed Cretaceous volcanic system at least 800 km across strike. The Jaglot–Chalt–Dras–Shyok volcanics exhibit predominant tholeiitic-calc-alkaline signatures, with a range of arc-related facies/tectonic settings. A younger, post-collisional, Tertiary silicic volcanic system (the Shamran–Dir–Dras-2–Khardung volcanics) lie unconformably upon Cretaceous basement, and erupted within an intra-continental tectonic setting. Kohistan–Ladakh tectonic model controversies remain. In essence, isotope-focused researchers prefer later (Tertiary) collisions, whilst structural field-geology-orientated researchers prefer an older (Cretaceous) age for the Northern/Shyok Suture.
Дисертації з теми "Tholeiitic volcanics"
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Claoue-Long, J. C. "Archaen komatiitic and tholeiitic volcanics at Kambalda, Western Australia." Thesis, University of Southampton, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375758.
Повний текст джерела
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Reindel, Jenna L. "The Origin of Basalt and Cause of Melting Beneath East Antarctica as Revealed by the Southernmost Volcanoes on Earth." Bowling Green State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1542379105898001.
Повний текст джерела
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Massey, Erica A. "A comparative study of glaciovolcanic palagonitization of tholeiitic and alkaline sideromelane in Helgafell, Iceland and Wells Gray-Clearwater Volcanic Field, BC, Canada." Thesis, University of British Columbia, 2017. http://hdl.handle.net/2429/61474.
Повний текст джерелаАнотація:
Pleistocene glaciovolcanic eruptions occurred frequently beneath continental-scale ice sheets producing vitric, fragmental volcanic deposits in Helgafell, Iceland (tholeiitic basalt) and Wells Gray, BC, Canada (alkali olivine basalt). They are highly susceptible to hydrothermal alteration that transforms sideromelane (basaltic volcanic glass) into palagonite (early amorphous material) and secondary minerals (i.e. zeolites, clays and sulfides). Compositional controls, mass transfer and geochemical-textural relationships are investigated by optical microscopy and analyses of major (12) and trace (32) elements in glass-palagonite pairs by Electron Microprobe Analysis (EMPA), Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS), and geochemical modelling. Helgafell’s thinner (6-10 m vs. 10-20 m) palagonite rims demarcate highly vesicular (30.2% vs. 4.9%) sideromelane that has more secondary minerals (1.4% vs. 0.5%) than Wells Gray’s microlite-rich (12.3% vs. 0.1%) sideromelane. The thicknesses of palagonite rims are similar whether the sideromelane is unaltered or completely altered.
Multi-dimensional scaling confirms that sideromelane composition, reflecting igneous processes, strongly controls the chemistry of palagonite. A comparison of element behavior in the palagonite from both localities reveals a tendency for water-soluble cations (Cl, K, Na, Rb, Cu, Mn, P) to correlate with water concentrations. Plots of element ratios (Nb/Y vs La/Nd; Sc/Ta vs Zr/Th) calculated from “immobile” elements show that palagonite from Wells Gray and Helgafell are distinct, and have ratios that are similar to sideromelane that produced the palagonite. Thus some palagonite compositions reflect primary magma compositions based on immobile elements. Gresens mass transfer calculations confirm minimal movement of these elements during palagonitization. However, the same calculations reveal a pattern of Cu, Cl, Ni, Rb and U addition and Na, Ca, Mg, P, V and Mn removal that is similar at both localities.
Microprobe traverses identified eight prominent trends across the glass-palagonite interface and palagonite rim, which do not appear to be controlled by sideromelane composition. Several element concentrations decrease in palagonite, including Si (by ~3-10%), Al, Ca and Na, while Ti, Fe and Mg concentrations increase. Locally, the palagonite has an inner Ti-rich zone. The gradual increase in Mg across the palagonite rim may be indicative of changes in solubility and pH.Irving K. Barber School of Arts and Sciences (Okanagan)
Earth and Environmental Sciences, Department of (Okanagan)
Graduate
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Van, Noord Kenrick A. A. "Deep-marine sedimentation and volcanism in the Silverwood Group, New England Fold Belt, Australia." Thesis, Queensland University of Technology, 1999.
Знайти повний текст джерелаАнотація:
In eastern Australia, the New England Fold Belt (NEFB) comprises an ancient convergent margin that was active from the Paleozoic until the late Mesozoic. Considerable effort has been expended in understanding the development of this margin over the past twenty years. However, proposed tectonic models for the orogen have either been too broad, ignoring contradictory local evidence, or too locally specific without paying attention to the 'big picture'. The research presented in this work addresses the issue of appropriate scale and depth of geological detail by studying the NEFB at the terrane-scale. Using one succession, the Silverwood Group of southeast Queensland, this work demonstrates that detailed sedimentological studies and basin analysis at the terrane-scale can help to refine hypotheses regarding the tectonic evolution of the NEFB.
The Silverwood Group (Keinjan terrane), located approximately 140 km southwest of Brisbane, Australia, is a succession of arc-related basins that developed within an ancient intraoceanic island-arc during the mid-Cambrian to Late Devonian. From the base of the succession, the group consists of five formations totalling -9700 m. These include the Risdon Stud Formation (2500 m), Connolly Volcanics (2400 m), Bald Hill Formation (2450 m), Ormoral Volcanics (600 m) and the Bromley Hills Formation (1700 m). The Long Mountain Breccia Member (300m) is a separate unit which forms the lower part of the Bromley Hills Formation. The entire succession has been thrust west over the Late Devonian to Early Carboniferous Texas beds. Elsewhere, the Silverwood Group is unconformably overlain by and faulted against Early to Late Permian units including the Rokeby beds, Wallaby beds, Tunnel beds, Fitz Creek beds, Eight Mile Creek beds, Rhyolite Range beds and Condamine beds. Of these Permian units, all but the Condamine beds form part of the Wildash Succession. To the west, southwest and south, the Silverwood Group is intruded by the Late Triassic Herries and Stanthorpe Adamellites. All of these sequences and the two plutonic intrusives are unconformably overlain by the Jurassic sediments of the Marburg Sandstone.
The Silverwood Group and Texas beds consist of various lithologies including grey, purple- grey, green and green-grey volcaniclastic conglomerates, sandstones, siltstones or mudstones, massive and laminated chert, polymict or monomict breccias, muddy breccias, muddy sandstones, and volcanic rocks. Volcanic rocks include various tholeiitic metabasites, dolerite, meta-andesites and infrequent metadacite. In the Silverwood Group, these volcanic rocks are often accompanied by mafic pyroclastic rocks (e.g. peperite and hyaloclastite). Facies analyses of these lithologies has led to the recognition of 19 deep-marine turbiditic and volcanic/volcaniclastic facies that were deposited by three main processes: i) gravity-flow processes (e.g. low- and high-density volcaniclastic turbidites and mass-flows), ii) chemical/biological processes (siliceous oozes- chert) and iii) direct initiation by volcanic processes (e.g. flows, hypabyssal intrusions and associated pyroclastic facies).
For the Silverwood Group, the defined facies occur in distinct vertical associations that form recognisable 3rd and 4th-order architectural elements such as channel, levee, suprafan lobe, outer-fan, basin plain, mass transport complex, volcanic flows, syn-sedimentary sills and syn-sedimentary emergent cryptodomes. These architectural elements are represented in a series of deep-marine depositional environments including slope, shelf-edge failure, submarine-fan and subaqueous basaltic volcanoes. The Risdon Stud Formation and parts of the Connolly Volcanics were deposited along a 'normal' clastic or mud, mud/sand-rich and/or sand/mud-rich slope. Both upper and lower slope environments are represented and in both formations, the slope is speculated to have faced eastwards and prograded away from an active arc located west. Sediments from both successions accumulated at palaeodepths of 1200 to 2000 m.
Although sediments from the upper part of the Bald Hill Formation were also deposited on a slope, these sequences have subsequently collapsed into the depocentre to form extensive slump deposits accompanied by olistoliths of older arc crust. The lower part of the Bald Hill Formation formed by similar processes, although the failure was far more extensive (>20 km along strike). This latter part of the formation is interpreted to be a major shelf-edge failure succession. Upper parts of the Bald Hill Formation also accumulated at palaeodepths of 1200 to 2000 m, but the deposition of these sediments occurred farthest from the shelf and at the greatest depth compared to the Risdon Stud Formation and Connolly Volcanics. Lower parts of the Bald Hill Formation were deposited at palaeodepths of approximately 1700 m.
Subaqueous basaltic volcanoes are prominent in the Connolly Volcanics, Bald Hill Formation and Ormoral Volcanics. In the Bald Hill Formation, igneous rocks were emplaced into the shelf-edge failure succession as a series of syn-sedimentary sills and cryptodomes. These high-level hypabyssal rocks occasionally became emergent above the sediment-water interface, whereupon they were partially resedimented. In some parts of the Bald Hill Formation, the hypabyssal intrusions were blanketed by basin plain deposits that are contemporaneous with the slumps and olistoliths in the upper part of the formation. The intrusive rocks were emplaced at 1700 m palaeodepth.
Unlike the Bald Hill Formation, the Ormoral Volcanics and lower parts of the Connolly Volcanics form thick accumulations of extrusive volcanic and pyroclastic rocks that built a significant volcanic pile. Volcanic and pyroclastic facies within these successions were deposited proximal to their source (0-10 km of vent). Extrusive rocks within the Ormoral Volcanics are thought to be derived from intrabasinal fissure-vents located at palaeodepths of 1700 to 3100 m. Igneous rocks from the Connolly Volcanics, Bald Hill Formation and Ormoral Volcanics have the petrological and geochemical characteristics of back-arc basin basalts (BAB) that were sourced from undepleted to slightly enriched Fertile MORB Mantle-wedge (FMM). The FMM material was variably enriched in trace elements by fluids derived from the subducting slab prior to emplacement of the igneous rocks. Immediately following emplacement, these rocks were hydrothermally metamorphosed under conditions of low-pressure and transitional low to high-temperature (200-300 °C). By contrast, igneous rocks within the Texas beds lack enrichment in subduction components and are characteristic of N-MORB.
The Bromley Hills Formation is a sand-rich point-source submarine fan deposited at palaeodepths of 500 to 2000 m. The fan was initiated by a mass transport complex resulting from subaerial collapse of a basaltic-andesitic stratovolcano. The submarine fan is characterised by two repetitive stages of retrogressive sedimentation during which channel-levee elements (inner-fan channels) are overlain by suprafan lobe elements (mid-fan) and then by outer-fan deposits as sea-level rises within the depocentre. Both inner-fan channels and suprafan lobes show centralised stacking patterns with limited lateral migration that indicate the depocentre was laterally restricted during sedimentation (e.g. submarine ridges). The Bromley Hills Formation exhibits all the characteristics typical of an active margin fan that formed by a combination of tectonic stage initiation followed by eustatically controlled regressive deposition.
Volcaniclastic sediments of the Silverwood Group range in composition from lithic to lithic- feldspathic wackes and arenites, although they are mainly lithic or feldspathic-lithic wackes and arenites. Many samples are tuffaceous (25-75% pyroclasts), particularly those from the Connolly Volcanics, Ormoral Volcanics and Bromley Hills Formation. Samples in the Bald Hills Formation and Texas beds can be classified as quartz-rich. The majority of the Silverwood Group was sourced from an undissected intraoceanic island-arc, although sediments within the Bald Hill Formation exhibit a provenance that is characteristic of uplift within the arc (recorded as a 'strike-slip continental arc' model). Epiclastic sediments from the Texas beds were sourced from a transitional to dissected continental arc.
Formations of the Silverwood Group were mostly deposited in a series of intra-arc basins within an ancient intra-oceanic island arc, although the lowermost formation developed in a marginal basin (Risdon Stud Formation). All of the basins were located east of the active arc (behind the arc), keeping in mind the present location of the Group relative to the Texas-Coffs Harbour megafold. The entire succession formed during four-phases of arc-related basin development that coincide with major changes in the strain regime of the arc. From the base of the succession, these changes are: I) mid Cambrian to late Silurian marginal basin sedimentation- relative compression within the arc (Risdon Stud Formation), II) late Silurian to Early Devonian intra-arc rifting- relative extension within the arc (Connolly Volcanics), Ill) Early to early Middle Devonian basin collapse followed by intra-arc rifting- relative extension to compression (Bald Hill Formation and Ormoral Volcanics) and IV) early Middle to Late Devonian intra-arc submarine fan sedimentation- relative compression (Bromley Hills Formation).
Comparing the Silverwood Group against equivalent terranes of Cambrian to Devonian age within the New England Fold Belt (NEFB) suggests that the Gamilaroi terrane, Calliope Volcanic Assemblage, Willowie Creek beds and Silverwood Group all formed as one intraoceanic island-arc during the Early to Late Devonian. Prior to this, significant differences in the sedimentological evolution of these terranes suggests that they occupied different positions relative to each other within the one arc. It is proposed that the NEFB formed as a result of dual west-directed subduction zones during the Cambrian to Middle Devonian period. During this time, a single intraoceanic island-arc located seaward of the Australian craton developed above a west-directed subduction zone. This arc was separated from the craton by a marginal sea. A second west-directed subduction zone was located beneath a continental arc developed on the Australian craton. Cambrian to Early Devonian terranes within and along the Peel Fault are proposed to form a part of the ancient subduction zone present beneath the intraoceanic island-arc (Weraerai and Djungati terranes). Collision of the intraoceanic island-arc occurred during the Late Devonian, at which point west-directed subduction occurred beneath the Australian craton and the accreted intraoceanic island-arc. Following collision, a new continental volcanic arc was established that was active during the Late Devonian to Early Carboniferous.
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Pflumio, Catherine. "Histoire volcanique et hydrothermale du massif de salahi : implications sur l'origine et l'evolution de l'ophiolite de semail (oman)." Paris, ENMP, 1988. http://www.theses.fr/1988ENMP0112.
Повний текст джерелаАнотація:
L'etude petrographique et geochimique de l'ophiolite de semail (massif salahi, oman) qui represente le plus vaste affleurement de lithosphere oceanique fossile permet de distinguer 3 phases de volcanisme, presentant des rapports ta/th anormaux qui sont interpretes comme les temoins d'une anomalie mantellaire regionale. Un modele d'evolution en contexte oceanique franc est propose. L'etude des differents episodes de circulation hydrothermale est egalement abordee
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Dissler, Eric. "Evolution geodynamique cadomienne du nord-cotentin (massif armoricain)." Caen, 1987. http://www.theses.fr/1987CAEN2048.
Повний текст джерелаАнотація:
La structuration actuelle des terrains brioveriens resulte en grande partie de l'evolution tectono-metamorphique varisque. La chaine cadomienne accuse une vergence nord-ouest. L'identification geochimique des series volcaniques brioveriennes revele une affinite tholeitique generalisee. Une tendance calcoalcaline s'exprime en revanche au sein du batholite de la hague. L'enchainement des premieres etapes de l'evolution geodynamique cadomienne est ainsi etablie, le magmatisme du brioverien inferieur traduisant le fonctionnement d'un dispositif arcs insulaires-bassins marginaux de type marge ouest du pacifique, installe sur des lambeaux de croute pentevrienne
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Dupont, Pierre-Luc. "Pétrologie et géochimie des ensembles magmatiques pharusien I et II, dans le rameau oriental de la chaîne pharusienne (Hoggar, Algérie) : Implications géodynamiques pour l'évolution d'une chaîne mobile au protérozoïque supérieur." Nancy 1, 1987. http://www.theses.fr/1987NAN10332.
Повний текст джерелаАнотація:
Au pharusien I, la série de timesselarsine révèle l'épanchement de basaltes, d'affinité transitionnelle a faiblement alcaline dont le site géodynamique serait celui d'un "rift" en domaine continental. Vient ensuite une série ultrabasique/basique dont le site le plus probable est celui d'arc insulaire ou de bassin marginal. Le troisième épisode est représenté par deux ensembles : un lié à un domaine de type arc insulaire, l'autre montrant une évolution vers une marge continentale active. Au pharusien II, la série d'anded est intrudée par des dolérites et des roches volcaniques en liaison avec un site de type arc insulaire. La série d'Irrellouchem est liée à un site d'arc insulaire ou de marge continentale active. Les données isotopiques du strontium obtenues sur ces deux séries impliquent une contribution mantellique importante. Le dernier épisode pharusien est représenté par les roches du batholite de Tin Tekadiouit
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Woodget, A. L. "The petrology, geochemistry and tectonic setting of basic volcanics on the Stuart Shelf and in the Adelaide Geosyncline, South Australia." Thesis, 1987. http://hdl.handle.net/2440/86641.
Повний текст джерелаАнотація:
This item is only available electronically.In 1980, von der Borch suggested that the Adelaide Geosyncline formed as a result of a rift initiated in the Late Proterozoic. In 1984, Gunn added further to the idea, and proposed that the Roopena Volcanics represented alkaline igneous activity associated with the initial doming phase. The basaltic lavas of Depot Creek, Port Pirie, Wooltana, the Adelaide Geosyncline, and the Beda Volcanics represent tholeiitic flood basalts from a later rifting stage, with the Gairdner Dyke Swarm acting as feeder dykes to the basalts. In hand specimen the volcanics look very similar, i.e. red-brown to green-grey fine vesicular basalts, but in thin section they are quite different. The Beda Volcanics are merocrystalline with an intersertal texture, the main mineral being plagioclase with small patches of subophitic augite (maximum 10%). The Gairdner Dyke Swarm rocks consist of either fine grained, curved branching augite with coarse laths of plagioclase and pehnocrysts of olivine set in an iron rich glass, or coarser grained holocrystalline ophitic rocks. The Depot Creek volvanics have a fine grained intersertal texture, consisting of potassium feldspar and recrystallised glass. The Port Pirie Volcanics are interbedded with both Calanna Group and Emeroo Subgroup sediments. The Emeroo Volcanics are intersertal fine grained rocks containing potassium feldspar and minor pyroxene set in an iron rich glassy ground mass. The Calanna Volcanics are subophitic in texture. Geochemically all the volcanics except the Port Pirie Volcanics are very similar, with the Beda Volcanics and Gairdner Dyke Swarm being the most fractionated. Magma chamber fractionation simulation studies suggest that the Gairdner Dykes were extruded from a crustal magma chamber of much greater depth, but the similar geochemistry suggests they may have stemmed from the same magma chamber as the other volcanics. Geochemical discrimination diagrams indicate the volcanics are tholeiitic continental flood basalts, and this is reinforced by using a spidergram plot developed by Pearce (1979). Comparison of these volcanics with volcanics from the central Karoo Province and northern Utah and southeastern Idaho on spidergrams show very similar trace element patterns. The basic volcanics of Depot Creek, Wooltana, and the Beda Volcanics, along with the Gairdner Dyke Swarm represent co-magmatic tholeiitic igneous activity associated with the Spencer Gulf rift. The more enriched Port Pirie volcanics were extruded at a later stage of the reactivation of the rift.
Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Earth and Environmental Sciences, 1987
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Annell, Heidi. "Petrology and geochemistry of the 25 MA Mt. Marion dufresne basaltic section on the Kerguelen Archipelago : constraining the transition from tholeiitic to mildly alkalic volcanism on a major oceanic island." Thesis, 2005. http://hdl.handle.net/2429/16584.
Повний текст джерелаАнотація:
Flood basalts on the - 6500 km² Kerguelen Archipelago in the southern Indian
Ocean formed in an intraplate location on the Antarctic plate between 29-24 Ma as the
Southeast Indian Ridge migrated from - 225 to - 400 km northeast relative to the
Kerguelen hotspot. A - 700 m section of basalts exposed at Mt. Marion Dufresne, in the
southern part of the Plateau Central, contains both transitional-tholeiitic and mildly
alkalic lavas (A.I. -0.8 to 2.0) that are geochemically and isotopically variable, and
captures an important period of time (-1 Myr) near the end of flood basalt volcanism on
the Kerguelen Archipelago. The basal 300 m of the section consists of low-MgO (<5.2 wt.
%) predominantly aphyric lavas characterized by a limited range of "enriched" isotopic
compositions (¹⁷⁶Hf/¹⁷⁷Hf =.0.28282-0.28287; ⁸⁷Sr/⁸⁶Sr = 0.7048-0.7050; ¹⁴³Nd / ¹⁴⁴Nd =
0.5126-0.5127; ²⁰⁷Pb / ²⁰⁴Pb = 15.54-15.56) similar to compositions observed in the
enriched 24-25 Ma mildly alkalic lavas to the east and southeast (e.g. Mt. Crozier). This
aphyric sequence of basalts appears to represent a "steady state" magmatic system where
differentiation occurred primarily in a solid-dominated (mush or slurry) environment.
Highly calcic (>An ₈₀) plagioclase compositions observed in intercalated plagioclasephyric
and ultraphyric basalts from the upper part of this interval signal a change in
crystallization environments to relatively shallow (-5-6 km) magma storage and relatively
hydrous conditions (>3 wt.% H₂0 ). The low-MgO basaltic lavas are overlain by a thick
(-400 m) succession of olivine-phyric high-MgO basalts (7.1-11.4 wt.%) that is
interpreted to represent an interval of increased magma supply and eruptive flux. Olivine
whole-rock Fe/Mg relations indicate that olivine phenocrysts with ~Fo ₈₀-₈₆ are in
equilibrium with parental magma compositions of 8-10 wt% MgO. Unlike the low-MgO
lavas, these high-MgO basalts span a range of "depleted" isotopic compositions
(⁷⁶Hf/¹⁷⁷Hf = 0.28292-0.28300, ⁸⁷Sr/⁸⁶Sr = 0.7040-0.7046, ¹⁴³Nd / ¹⁴⁴Nd = 0.5127-0.5128,
and ²⁰⁷Pb / ²⁰⁴Pb = 15.49-15.52) and represent the first documented occurrence of a
depleted mantle component in mildly alkalic basalts from the Kerguelen Archipelago.
The presence of this depleted mantle component, which is compositionally similar to that
observed in the older 28-29 Ma basalts in the northern part of the archipelago, reflects a
short term increase in the extent of melting beneath the oceanic lithosphere and renewed
interaction between Southeast Indian Ridge MORB-type asthenosphere and the enriched
component of Kerguelen mantle plume at 25 Ma.Science, Faculty of
Earth, Ocean and Atmospheric Sciences, Department of
Graduate
Книги з теми "Tholeiitic volcanics"
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Bridges, John C. Evolution of the Martian Crust. Oxford University Press, 2017. http://dx.doi.org/10.1093/acrefore/9780190647926.013.18.
Повний текст джерелаАнотація:
This is an advance summary of a forthcoming article in the Oxford Encyclopedia of Planetary Science. Please check back later for the full article.Mars, which has a tenth of the mass of Earth, has cooled as a single lithospheric plate. Current topography gravity maps and magnetic maps do not show signs of the plate tectonics processes that have shaped the Earth’s surface. Instead, Mars has been shaped by the effects of meteorite bombardment, igneous activity, and sedimentary—including aqueous—processes. Mars also contains enormous igneous centers—Tharsis and Elysium, with other shield volcanoes in the ancient highlands. In fact, the planet has been volcanically active for nearly all of its 4.5 Gyr history, and crater counts in the Northern Lowlands suggest that may have extended to within the last tens of millions of years. Our knowledge of the composition of the igneous rocks on Mars is informed by over 100 Martian meteorites and the results from landers and orbiters. These show dominantly tholeiitic basaltic compositions derived by melting of a relatively K, Fe-rich mantle compared to that of the Earth. However, recent meteorite and lander results reveal considerable diversity, including more silica-rich and alkaline igneous activity. These show the importance of a range of processes including crystal fractionation, partial melting, and possibly mantle metasomatism and crustal contamination of magmas. The figures and plots of compositional data from meteorites and landers show the range of compositions with comparisons to other planetary basalts (Earth, Moon, Venus). A notable feature of Martian igneous rocks is the apparent absence of amphibole. This is one of the clues that the Martian mantle had a very low water content when compared to that of Earth.The Martian crust, however, has undergone hydrothermal alteration, with impact as an important heat source. This is shown by SNC analyses of secondary minerals and Near Infra-Red analyses from orbit. The associated water may be endogenous.Our view of the Martian crust has changed since Viking landers touched down on the planet in 1976: from one almost entirely dominated by basaltic flows to one where much of the ancient highlands, particularly in ancient craters, is covered by km deep sedimentary deposits that record changing environmental conditions from ancient to recent Mars. The composition of these sediments—including, notably, the MSL Curiosity Rover results—reveal an ancient Mars where physical weathering of basaltic and fractionated igneous source material has dominated over extensive chemical weathering.
Частини книг з теми "Tholeiitic volcanics"
1
Sisson, Thomas W., Peter W. Lipman, and Jiro Naka. "Submarine alkalic through tholeiitic shield-stage development of Kīlauea volcano, Hawai'i." In Hawaiian Volcanoes: Deep Underwater Perspectives, 193–219. Washington, D. C.: American Geophysical Union, 2002. http://dx.doi.org/10.1029/gm128p0193.
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Lagorio, Silvia Leonor, Haroldo Vizán, and Silvana Evangelina Geuna. "Geodynamical Setting for the Tholeiites of Misiones Province (North-eastern Argentina) in the Context of the PMP and the Alkaline Volcanism of Córdoba Province (Central Argentina)." In Early Cretaceous Volcanism in Central and Eastern Argentina During Gondwana Break-Up, 129–35. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-29593-0_5.
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Sullivan, Raymond, Ryan P. Fay, Carl Schaefer, Alan Deino, and Stephen W. Edwards. "Neogene volcanism on the eastside of Mount Diablo, Contra Costa County, California." In Regional Geology of Mount Diablo, California: Its Tectonic Evolution on the North America Plate Boundary. Geological Society of America, 2021. http://dx.doi.org/10.1130/2021.1217(11).
Повний текст джерелаАнотація:
ABSTRACT Two spatially separated areas of Neogene volcanic rocks are located on the northeast limb of the Mount Diablo anticline. The southernmost outcrops of volcanics are 6 km east of the summit of Mount Diablo in the Marsh Creek area and consist of ~12 hypabyssal dacite intrusions dated at ca. 7.8–7.5 Ma, which were intruded into the Great Valley Group of Late Cretaceous age. The intrusions occur in the vicinity of the Clayton and Diablo faults. The rocks are predominantly calc-alkaline plagioclase biotite dacites, but one is a tholeiitic plagioclase andesite. Mercury mineralization was likely concomitant with emplacement of these late Miocene intrusions. The northern most outcrops of Neogene volcanic rocks occur ~15 km to the north of Mount Diablo in the Concord Naval Weapons Station and the Los Medanos Hills and are probably parts of a single andesite flow. A magnetometer survey indicates that the flow originated from a feeder dike along the Clayton fault. The lava flow is flat-lying and occu pies ancient stream channels across an erosional surface of tilted Markley Sandstone of middle Eocene age. New radiometric dates of the flow yield an age of 5.8–5.5 Ma, but due to alteration the age should be used with caution. The flow is a calc-alkaline andesite rich in clinopyroxene and plagioclase. What appear to be uplifted erosional remnants of the flow can be traced northeastward in the Los Medanos Hills across a surface of tilted Cenozoic rocks that eventually rest on formations as young as the Lawlor Tuff dated at 4.865 ± 0.011 Ma. This stratigraphic relationship suggests that the andesite flow is probably late Pliocene in age and was impacted by the more recent uplift of the Los Medanos Hills but postdates the regional folding and faulting of the rocks of Mount Diablo. In terms of timing, location, and composition, the evidence suggests these two areas of dacitic and andesitic volcanics fit into a series of migrating volcanic centers in the California Coast Ranges that erupted following the northward passage of the Mendocino Triple Junction.
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Cahoon†, Emily B., Martin J. Streck†, and Mark Ferns†. "Flood basalts, rhyolites, and subsequent volcanism of the Columbia River magmatic province in eastern Oregon, USA." In From Terranes to Terrains: Geologic Field Guides on the Construction and Destruction of the Pacific Northwest, 301–52. Geological Society of America, 2021. http://dx.doi.org/10.1130/2021.0062(08).
Повний текст джерелаАнотація:
ABSTRACT The Miocene Columbia River Basalt Group (CRBG) is the youngest and smallest continental flood basalt province on Earth. This flood basalt province is a succession of compositionally diverse volcanic rocks that record the passage of the Yellowstone plume beneath eastern Oregon. The compositionally and texturally varied suite of volcanic rocks are considered part of the La Grande–Owyhee eruptive axis (LOEA), an ~300-km-long, north-northwest–trending, Middle Miocene to Pliocene volcanic belt that extends along the eastern margin of the Columbia River flood basalt province. Volcanic rocks erupted from and preserved within the LOEA form an important regional stratigraphic link between the flood basalt–dominated Columbia Plateau to the north, the north and bimodal basalt-rhyolite volcanic fields of the Snake River Plain to the east, the Owyhee Plateau to the south, and the High Lava Plains to the south and east; the latter two have time transgressive rhyolite centers that young to the east and west, respectively. This field-trip guide details a four-day geologic excursion that will explore the stratigraphic and geochemical relationships among mafic rocks of the CRBG and coeval and compositionally diverse silicic rocks associated with the early trace of the Yellowstone plume and High Lava Plains in eastern Oregon. The trip on Day 1 begins in Portland then traverses across the western axis of the Blue Mountains, highlighting exposures of the widespread, Middle Miocene Dinner Creek Welded Tuff and aspects of the Picture Gorge Basalt lava flows and northwest-striking feeder dikes situated in the central part of the CRBG province. Travel on Day 2 progresses eastward toward the eastern margin of the LOEA, examining a transition linking the Columbia River Basalt province with a northwestward-younging magmatic trend of silicic volcanism of the High Lava Plains in eastern Oregon. Initial field stops on Day 2 focus on the volcanic stratigraphy northeast of the town of Burns, which includes regionally extensive Middle to Late Miocene ash-flow tuffs and lava flows assigned to the Strawberry Volcanics. Subsequent stops on Day 2 examine key outcrops demonstrating the intercalated nature of Middle Miocene tholeiitic CRBG flood basalts, temporally coeval prominent ash-flow tuffs, and “Snake River–type” large-volume rhyolite lava flows cropping out along the Malheur River. The Day 3 field route navigates to southern parts of the LOEA, where CRBG rocks are associated in space and time with lesser known and more complex silicic volcanic stratigraphy forming Middle Miocene, large-volume, bimodal basalt-rhyolite vent complexes. Key stops will provide a broad overview of the structure and stratigraphy of the Middle Miocene Mahogany Mountain caldera and of the significance of intercalated sedimentary beds and Middle to Late Miocene calc-alkaline lava flows of the Owyhee basalt. Initial stops on Day 4 will highlight exposures of Middle to Late Miocene silicic ash-flow tuffs, rhyolite domes, and calc-alkaline lava flows overlying the CRBG across the northern and central parts of the LOEA. The later stops on Day 4 examine more silicic lava flows and breccias that are overlain by early CRBG-related rhyolite eruptions. The return route to Portland on Day 4 traverses the Columbia River gorge westward from Baker City. The return route between Baker and Portland on Day 4 follows the Columbia River gorge and passes prominent basalt outcrops of large volume tholeiitic flood lavas of the Grande Ronde, Wanapum, and Saddle Mountains Formations of the CRBG. These sequences of basaltic and basaltic andesite lavas are typical of the well-studied flood basalt dominated Columbia Plateau, and interbedded silicic and calc-alkaline lavas are conspicuously absent. Correlation between the far-traveled CRBG lavas and calcalkaline and silicic lavas considered during the excursion relies on geochemical fingerprinting and dating of the mafic flows and dating of sparse intercalated ashes.
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Melluso, Leone, Vincenzo Morra, Pietro Brotzu, Massimo D'Antonio, and Lucia Bennio. "Petrogenesis of the Late Cretaceous tholeiitic magmatism in the passive margins of northeastern Madagascar." In Volcanic Rifted Margins. Geological Society of America, 2002. http://dx.doi.org/10.1130/0-8137-2362-0.81.
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Dostal, Jaroslav, Pierre Jutras, and Reginald A. Wilson. "Geochemical and Nd isotopic constraints on the origin of uppermost Silurian rhyolitic rocks in the northern Appalachians (northern New Brunswick): Tectonic implications." In New Developments in the Appalachian-Caledonian- Variscan Orogen. Geological Society of America, 2022. http://dx.doi.org/10.1130/2021.2554(06).
Повний текст джерелаАнотація:
ABSTRACT Voluminous bimodal volcanic rocks of the Silurian (ca. 422–420 Ma) Dickie Cove Group in the Ganderia domain of northern New Brunswick, Canada, are subaerial units that were deposited in an extensional setting, with the mafic types corresponding to continental tholeiites. Felsic rocks are rhyolites with calc-alkaline affinities. They exhibit geochemical characteristics that are typical of A2-type felsic magmas, such as enrichments in the incompatible elements Zr, Nb, and Y, as well as high FeO*/(FeO* + MgO) and Ga/Al ratios. Their εNd(t) values are positive (+0.7 to +3.4) but lower than those of the associated basalts. Saturation thermometry has yielded average zircon crystallization temperature estimates for the rhyolites that are well above 900 °C. The geochemical data indicate that the felsic melts were likely sourced from heterogeneous Neoproterozoic lower crust and generated by dehydration melting triggered by heat derived from underplated mafic magma. Parent melts of the rhyolites underwent fractional crystallization in a complex magma chamber prior to eruption. The Nd isotopic data suggest that the lower crust of Ganderia is similar to that of Avalonia in northern mainland Nova Scotia, and that the two microcontinents shared a common Neoproterozoic history and origin as continental blocks rifted from neighboring parts of Gondwana. The tectono-magmatic setting of the Dickie Cove Group volcanic rocks is interpreted as being related to Pridolian, post-Salinic relaxation and slab breakoff, which generated volcanism initially constrained within the Chaleur zone of the Chaleur Bay synclinorium, a large domain of the northern Appalachians. This was followed later in the Pridolian by extensional collapse and widening of the area of magmatic activity, which then prograded into the Tobique zone farther to the southwest.
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Vaughan, Jeremy, Carl E. Nelson, Guillermo Garrido, Jose Polanco, Valery Garcia, and Arturo Macassi. "Chapter 20: The Pueblo Viejo Au-Ag-Cu-(Zn) Deposit, Dominican Republic." In Geology of the World’s Major Gold Deposits and Provinces, 415–30. Society of Economic Geologists, 2020. http://dx.doi.org/10.5382/sp.23.20.
Повний текст джерелаАнотація:
Abstract The world-class Pueblo Viejo Au deposit in the central Dominican Republic is one of the largest high-sulfidation epithermal Au deposits globally, with past production plus resources and reserves of 41.7 million ounces (Moz) in the Moore and Monte Negro deposits. Mineralization occurs within a 2- × 2-km Early Cretaceous volcano-sedimentary basin filled with felsic volcanic and volcaniclastic rocks, interlayered carbonaceous sedimentary units, and underlying andesitic flows and tuffs. The volcanic stratigraphy was developed during a period of tholeiitic magmatism that transitioned to calc-alkaline magmatism at the time of emplacement of the late- to postmineral Monte Negro dike (~109 Ma). Additional geologic controls to mineralization include high-angle, NE- and NW-faulting, phreatomagmatic breccias, and possible volcanic domes. Mineralization is present across the stratigraphic sequence, with mineralization at Moore dominantly hosted within quartz-bearing volcaniclastic rocks and overlying carbonaceous sedimentary units, whereas that at Monte Negro is in the andesitic sequence as well as overlying epiclastic and sedimentary units. Alteration at the shallowest level is dominated by quartz-pyrophyllite, whereas alunite alteration defines the deep roots to the ore-forming environment. Mineralization comprises early disseminated-type and late veins filled with pyrite ± sphalerite. Hypogene ore is refractory in nature, with Au in solid solution or as mineral inclusions within arsenian pyrite. Re-Os ages of 113.4 ± 2.6 Ma for auriferous pyrite along with new geologic observations appear to confirm an Early Cretaceous age for mineralization, although Re-Os enargite ages suggest the possibility of a second mineralization event in the Eocene.
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Beccaluva, Luigi, Gianluca Bianchini, Costanza Bonadiman, Massimo Coltorti, Lorenzo Milani, Leonardo Salvini, Franca Siena, and Renzo Tassinari. "Intraplate lithospheric and sublithospheric components in the Adriatic domain: Nephelinite to tholeiite magma generation in the Paleogene Veneto volcanic province, southern Alps." In Cenozoic Volcanism in the Mediterranean Area. Geological Society of America, 2007. http://dx.doi.org/10.1130/2007.2418(07).
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Lustrino, Michele, Claudio Chiarabba, and Eugenio Carminati. "Igneous activity in central-southern Italy: Is the subduction paradigm still valid?" In In the Footsteps of Warren B. Hamilton: New Ideas in Earth Science. Geological Society of America, 2022. http://dx.doi.org/10.1130/2021.2553(28).
Повний текст джерелаАнотація:
ABSTRACT The Pliocene–Quaternary igneous record of the Tyrrhenian Sea area features a surprisingly large range of compositions from subalkaline to ultra-alkaline and from ultrabasic to acid. These rocks, emplaced within the basin and along its margins, are characterized by strongly SiO2-undersaturated and CaO-rich to strongly SiO2-oversaturated and peraluminous compositions, with sodic to ultrapotassic alkaline and tholeiitic to calc-alkaline and high-K calc-alkaline affinities. We focused on the different models proposed to explain the famous Roman Comagmatic Region, part of the Quaternary volcanism that spreads along the eastern side of the Tyrrhenian area, in the stretched part of the Apennines thrust-and-fold belt. We reviewed data and hypotheses proposed in the literature that infer active to fossil subduction up to models that exclude subduction entirely. Many field geology observations sustain the interpretation that the evolution of the Tyrrhenian-Apennine system was related to subduction of the western margin of Adria continental lithosphere after minor recycling of oceanic lithosphere. However, the lateral extent of the subducting slab in the last millions of years, when magmatism flared up, remains debatable. The igneous activity that developed in the last millions of years along the Tyrrhenian margin is here explained as originating from a subduction-modified mantle, regardless of whether the large-scale subduction system is still active.
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Smith, Alan L., M. John Roobol, Glen S. Mattioli, George E. Daly, and Joan E. Fryxell. "Providencia Island: A Miocene Stratovolcano on the Lower Nicaraguan Rise, Western Caribbean—A Geological Enigma Resolved." In Providencia Island: A Miocene Stratovolcano on the Lower Nicaraguan Rise, Western Caribbean—A Geological Enigma Resolved, 1–101. Geological Society of America, 2021. http://dx.doi.org/10.1130/2021.1219(01).
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ABSTRACT The Providencia island group comprises an extinct Miocene stratovolcano located on a shallow submarine bank astride the Lower Nicaraguan Rise in the western Caribbean. We report here on the geology, geochemistry, petrology, and isotopic ages of the rocks within the Providencia island group, using newly collected as well as previously published results to unravel the complex history of Providencia. The volcano is made up of eight stratigraphic units, including three major units: (1) the Mafic unit, (2) the Breccia unit, (3) the Felsic unit, and five minor units: (4) the Trachyandesite unit, (5) the Conglomerate unit, (6) the Pumice unit, (7) the Intrusive unit, and (8) the Limestone unit. The Mafic unit is the oldest and forms the foundation of the island, consisting of both subaerial and subaqueous lava flows and pyroclastic deposits of alkali basalt and trachybasalt. Overlying the Mafic unit, there is a thin, minor unit of trachyandesite lava flows (Trachyandesite unit). The Breccia unit unconformably overlies the older rocks and consists of crudely stratified breccias (block flows/block-and-ash flows) of vitrophyric dacite, which represent subaerial near-vent facies formed by gravitational and/or explosive dome collapse. The breccias commonly contain clasts of alkali basalt, indicating the nature of the underlying substrate. The Felsic unit comprises the central part of the island, composed of rhyolite lava flows and domes, separated from the rocks of the Breccia unit by a flat-lying unconformity. Following a quiescent period, limited felsic pyroclastic activity produced minor valley-fill ignimbrites (Pumice unit). The rocks of Providencia can be geochemically and stratigraphically subdivided into an older alkaline suite of alkali basalts, trachybasalts, and trachyandesites, and a younger subalkaline suite composed dominantly of dacites and rhyolites. Isotopically, the alkali basalts together with the proposed tholeiitic parent magmas for the dacites and rhyolites indicate an origin by varying degrees of partial melting of a metasomatized ocean-island basalt–type mantle that had been modified by interaction with the Galapagos plume. The dacites are the only phenocryst-rich rocks on the island and have a very small compositional range. We infer that they formed by the mixing of basalt and rhyolite magmas in a lower oceanic crustal “hot zone.” The rhyolites of the Felsic unit, as well as the rhyolitic magmas contributing to dacite formation, are interpreted as being the products of partial melting of the thickened lower oceanic crust beneath Providencia. U-Pb dating of zircons in the Providencia volcanic rocks has yielded Oligocene and Miocene ages, corresponding to the ages of the volcanism. In addition, some zircon crystals in the same rocks have yielded both Proterozoic and Paleozoic ages ranging between 1661 and 454 Ma. The lack of any evidence of continental crust beneath Providencia suggests that these old zircons are xenocrysts from the upper mantle beneath the Lower Nicaraguan Rise. A comparison of the volcanic rocks from Providencia with similar rocks that comprise the Western Caribbean alkaline province indicates that while the Providencia alkaline suite is similar to other alkaline suites previously defined within this province, the Providencia subalkaline suite is unique, having no equivalent rocks within the Western Caribbean alkaline province.
Тези доповідей конференцій з теми "Tholeiitic volcanics"
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Randall, John A. "PETROLOGY AND GEOCHRONOLOGY OF THE EOCENE BASALT OF FROST MOUNTAIN: THOLEIITIC VOLCANISM IN THE CENTRAL CASCADES, WASHINGTON." In GSA Annual Meeting in Seattle, Washington, USA - 2017. Geological Society of America, 2017. http://dx.doi.org/10.1130/abs/2017am-301044.
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Hudson, Sarah R., and Gary S. Michelfelder. "PETROGRAPHY AND PETROLOGY OF THE ALKALINE AND THOLEIITIC LAVAS FROM THE LA TETRA AREA, ZUNI-BANDERA VOLCANIC FIELD, NEW MEXICO." In GSA Annual Meeting in Phoenix, Arizona, USA - 2019. Geological Society of America, 2019. http://dx.doi.org/10.1130/abs/2019am-334691.
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Weber, Marion, Jose Fernando Duque-Trujillo, Susana Hoyos, Andres L. Cardenas, Jorge Gomez Tapias, and Rob Wilson. "MIOCENE THOLEIITIC AND CALK-ALKALINE MAGMATISM FROM THE NORTHERN COLOMBIAN ANDES – IMPLICATIONS FOR MAGMA PETROGENESIS IN THE NORTHERN VOLCANIC ZONE." In GSA Annual Meeting in Indianapolis, Indiana, USA - 2018. Geological Society of America, 2018. http://dx.doi.org/10.1130/abs/2018am-324534.
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Sleeper, Larissa, and Martin Streck. "OWYHEE BASALT - DEVELOPMENT OF CALC-ALKALINE VOLCANISM ON THE HEELS OF THOLEIITIC FLOOD BASALTS OF THE COLUMBIA RIVER PROVINCE." In Cordilleran Section-117th Annual Meeting-2021. Geological Society of America, 2021. http://dx.doi.org/10.1130/abs/2021cd-363172.
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Massey, Erica, John D. Greenough, and Ben Edwards. "A COMPARATIVE STUDY OF GLACIOVOLCANIC PALAGONITIZATION OF THOLEIITIC AND ALKALINE SIDEROMELANE AT HELGAFELL, ICELAND AND WELLS GRAY-CLEARWATER VOLCANIC FIELD, BC CANADA." In GSA Annual Meeting in Seattle, Washington, USA - 2017. Geological Society of America, 2017. http://dx.doi.org/10.1130/abs/2017am-306997.
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Satyana, A. H. "Ciletuh Subduction, West Java - New Findings, New Problems: Regional Implications to Cretaceous-Paleogene Convergence of Sundaland Margin and Its Petroleum Geology." In Indonesian Petroleum Association 44th Annual Convention and Exhibition. Indonesian Petroleum Association, 2021. http://dx.doi.org/10.29118/ipa21-g-29.
Повний текст джерелаАнотація:
Ciletuh, southwest Java has been well known as one of the places in Java where pre-Tertiary basement rocks are exposed (Verbeek and Fennema, 1896; Duyfjes, 1940; van Bemmelen, 1949; Sukamto, 1975). In plate tectonic point of view, Ciletuh has been known as place outcropping melange complex related to pre-Tertiary oceanic plate subduction (Thayyib et al., 1977). Ciletuh subduction regionally has been linked to the Cretaceous subduction zones of Luk Ulo/Karang Sambung (Central Java) and Meratus Mountains (South Kalimantan) (Hutchison, 1973; Asikin 1974; Hamilton, 1979). Ciletuh subduction however, has not been dated using metamorphic rocks formed in its subduction zone. Its link to Luk Ulo and Meratus subduction zone only based on the presence of melange, which also lacks of data Meanwhile, subduction zones of Luk Ulo and Meratus have been dated and analysed. We herewith present the results of new field studies and various analyses carried out in the last five years of the Ciletuh subduction complex. The indication of Cretaceous subduction has not found from the date measurement, Ciletuh shows Eocene related subduction. Most of the ophiolites were island-arc tholeiitic or island-arc basalt formed in supra-subduction zone. The overlying olistostrome deposits were younger than previously considered and lasted until early/middle Miocene. Some of the basaltic pillowed lava is considered as part of the ophiolite, while the ones at Gunung Badak is more likely a part of the early Miocene Jampang volcanism. Link of Ciletuh to Early Cretaceous subduction of Luk Ulo is not supported by geochronological data. The new knowledge of Ciletuh subduction implies the pre-Tertiary and Paleogene geology of Java, and petroleum prospectivities of the Paleogene objectives of southern West Java. New problems arise and need more field data and analyses to find out the answers.
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Dungan, Michael. "THOLEIITIC (TH) AND CALC-ALKALINE (CA) SERIES AT FRONTAL-ARC VOLCANOES OF THE 33.3-41.1°S PORTION OF THE ANDEAN SOUTHERN VOLCANIC ZONE (SVZ), CHILE: ASSESSING THE IMPACT OF CRUSTAL THICKNESS, PARENT MAGMA COMPOSITIONS, DIFFERENTIATION MECHANISMS, AND CONDITIONS OF MAGMA EVOLUTION." In 115th Annual GSA Cordilleran Section Meeting - 2019. Geological Society of America, 2019. http://dx.doi.org/10.1130/abs/2019cd-329089.
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Endrich, Alyssa, Matthew Brueseke, Alexander Karrasch, J. Christopher Haley, and Daniel P. Miggins. "CENOZOIC BASALTIC VOLCANISM IN THE CENTENNIAL VALLEY AND VICINITY: IMPLICATIONS FOR THE AREAL EXTENT OF SNAKE RIVER OLIVINE THOLEIITES ASSOCIATED WITH THE YELLOWSTONE HOTSPOT." In GSA Connects 2022 meeting in Denver, Colorado. Geological Society of America, 2022. http://dx.doi.org/10.1130/abs/2022am-383235.
Повний текст джерелаЗвіти організацій з теми "Tholeiitic volcanics"
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Hamilton, M. A. Tholeiitic and weakly alkalic basaltic volcanism of the Mugford Group, northern Labrador: preliminary geochemical results. Natural Resources Canada/ESS/Scientific and Technical Publishing Services, 1994. http://dx.doi.org/10.4095/193841.
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