Geological processes at the midocean ridges are responsible for the bulk of the earths heat loss and volcanic activity. At the solomon arc, the australian plate is presently subducted beneath the pacific plate. Islandarc basalt how is islandarc basalt abbreviated. Midpaleozoic initiation of the northern cordilleran marginal backarc. Summary map of japan showing the location of the main islands, cities, volcanoes, and numerous geological features mentioned in the text. You may, without any fee or cost, use, copy, modify. Software dedicated for the curation of geochemical data sets in. It should be noted that the overall hyperbolic trend shown in fig. The lava from beruvikurhraun is the only alkali basalt.
The debate on the onset of plate tectonics in the earths history has partially originated from the controversial criteria of using felsic crust to trace plate tectonics in the past. It is now fragmented into the siletz and crescent terranes siletzia. Our study shows that, contrary to what was previously. These magmas can normally be easily distinguished from calcalkaline basalts from more mature arc systems. The origin of primitive ocean island and island arc basalts.
The field for modern morb and ocean island basalts from the pacific and indian ocean regions is illustrated as a pale gray field. Basalt geochemistry and tectonic discrimination within. The other geochemical groups have distinct trace element. Subduction zones and island arcs university of leicester. Equation 2 yields values for k d that are in good agreement with the parameterization of toplis. The mineralogy of the basalts is broadly homogeneous, but all of them have suffered important seawater alteration. Geochemical constraints on the petrogenesis of arc. Based on the parallelism between petrographic boundaries. New mineralogical, geochemical, and isotope data in combination with. Titanium isotopes as a tracer for the plume or island arc. Pleistocene basaltic volcanism of kunashir island kuril island arc. Here, we demonstrate how ti isotope ratios can be used as a proxy for the affinity of felsic rocks to plume or island arc settings. Subduction of a high relief under the chugach terrane. Average majorelement compositions are tabulated for basalts.
The plate tectonics theory, however, cannot readily explain the widespread basaltic volcanism occurring in the interiors of tectonic plates. Typically, a deep oceanic trench, such as the marianastrench, bounds an island. They proposed a new class of volcanic rocks called fore. Geochemistry and mineralogy of basalts from the south mid. Basalts from the efate island group, central section of. Basalt geochemistry as a diagnostic indicator of tectonic. Cerium isotope geochemistry of ocean island basalts nature.
Isotopes and trace elements, in treatise on geochemistry. Island arc basalts are an important link in the chain of evidence that supports this model, as they display isotope signatures in common with both oceanfloor sediment2,4 and ocean island basalts1,5. The picrite occurrences appear to be linked to the subduction of young, hot oceanic crust and anomalous geotherms. The named volcanoes represent all those listed as rank a and a selected number of those listed as rank b by the japan meteorological agency japan meteorological agency, 2005. Much of the evidence for the operation of subduction on early earth is based on the geochemistry of volcanic rocks found in archean granitegreenstone terranes, particularly calcalkaline andesites, which commonly bear striking geochemical similarities to their counterparts from phanerozoic arc complexes barley et al. This software and related material data and documentation are made available by the u. This combination of morblike and islandarclike geochemistry is characteristic of backarc basin basalts. Marsh department of geology, rhodes university, grahamstown 6140, south africa received. How life on earth affected its inner workings geology page. A geological and geochemical study of the skidder basalt. In this paper, we investigate basalt samples dredged from four locations along the south midatlantic ridge ranging from 18.
Perfitphase relations of a highmg basalt from the aleutian island arc. Morganl the australian national university, canberra abstract. The composition of this sample would thus support the interpretation that the grenada basin developed through backarc spreading, and the grenadine platform consists of crust created in this way and subsequently uplifted e. Oxygen isotope geochemistry of oceanicarc lavas journal. Backarc basin and ocean island basalts in the narooma. The suggested discriminate diagrams helped to distinguish the volcanics recovered from different tectonic settings but group the ofb under one class i. Geochemical characterization of oceanic basalts using. A wellknown difference between the two is that island arc basalts are more oxidized than those.
The petrology and geochemistry of a metabasite belt along. The main arc miocenequaternary is dominated by weakly tholeiitic, with. Fundamental aspects concerning the origin of ocean island basalts and primitive island arc magmas are addressed using examples from the vanuatu arc, hawaii, and the tasmantid seamounts. Xls software is introduced for calculating primary magma composition and mantle potential temperature tp from an observed lava composition.
Subduction controls of hf and nd isotopes in lavas of the. The origin of midocean ridge basalts morb and island arc basalts iabisreasonablywellunderstoodasaresultofplatetectonic processes operating at plate boundaries. The geochemistry of four icelandic basalts is compared with that of other basalts along the midatlantic ridge. A wellknown difference between the two is that island arc basalts are more oxidized than those found at midocean ridges. Understanding the geochemistry of oil and gas reserves, from wellbore to basin. On the nbzry discrimination diagram of pearce and cann 1973, the hongshankou basalts plot in the combined field of morb, island arc tholeiite and calcalkali basalts fig. Kuno 4 suggests that highalumina basalts occur along the intermediate belt between these two provinces. Isotopic and trace element geochemical studies of ocean island basalts oibs have for many years been used to infer the presence of longlived approx 12 ga old compositional heterogeneities in the deep mantle related to recycling of crustal lithologies and marine and terrigenous sediments via subduction e. Geochemistry data suggest an intraoceanic island arc origin. Geochemistry of volcanic rocks in barton and weaver peninsulas, king george island, antarctica. The water content in the island arc basic magmas varies from almost zero value. Exposures of island arc crust provide an opportunity to directly observe. Some statistical evaluations and implications using the database georoc.
White department of earth and atmospheric sciences, cornell university, ithaca, new york 148531504. The basalts belong to the tholeiitic series and exhibit. Detailed petrologic study of a metabasite belt using different modern tools. Pearce 1982 used a crcesr discrimination diagram to distinguish between volcanic arc basalts, morb and wpb. International ocean discovery program iodp expedition 352 cored four sites in the. Geochemistry of oceanic islandarc and active continental margin volcanic suites. Rare earth and trace element patterns are comparable to altered basalt patterns. The only published geochemical work for the moyaleel kur ma. Geochemistry and geochronology of grenada and union. These basalts form small cones constructed upon a volcaniclastic apron principally composed of trachydacitic breccias. Archean andesites in the east yilgarn craton, australia.
Journal of volcanology and geothermal research, 32 1987 3549 35 elsevier science publishers b. Volcanic zone these oceanic island arc basalts cannot have. The south midatlantic ridge is a typical slowspreading ridge that represents a modern example to understand mantle composition and the evolution of midocean ridge magmatism. Yeo, jeong pil lee, jong ik hur, soon do and choi, byeongak 2004. Samples taken from the three main basaltic intervals were chemically analyzed.
Geologic, geochemical, and neodymium isotope evidence from the. Island arc picrites are restricted to a few localities including the lesser antilles, japan, vanuatu and the solomon islands. Implications for arc maturity and correlation with fossilized volcanic centers. Wholerock major and traceelement and mineral chemical data are presented for basaltic rocks from the main evolutionary stages of the kurile island arc, nw pacific. Backarc basin and ocean island basalts in the narooma accretionary complex, australia. Leonova ll 1977 geochemistry of quaternary volcanic rocks of the kurile island arc. Lavas from the galapagos islands and hawaii record in their geochemistry high t p maxima and large ranges in both t p and melt fraction over short horizontal distances, a result that is predicted by the mantle plume model. The lesser antilles island arc basaltic lavas, consisting of basalt and minor basaltic andesite. The samples were taken from cores 2101277a1w, 3r, 4r, and 5r at the positions listed in tables t1 and t2. The contours of earthquake depth 3, 5 gravity isostatic anomaly 6 and heat flow 7 appear to run approximately parallel with the elongation of the island arc of japan. Fundamental aspects concerning the origin of ocean island basalts and primitive island arc. At melville point, the succession has basal altered basalts overlain.
A leading but debated hypothesis for this difference is that oceanic crust is oxidized by oxygen and sulfate in the deep ocean before it is subducted into the mantle, delivering oxidized material to the mantle source of. Magma formation and its reflection in the volcanic process. Clsc is the central lau spreading centrei ocean drilling program sites 841, etc. Pdf geochemistry of oceanic islandarc and active continental. Geological survey usgs to be used in the public interest and the advancement of science. A backarc basin occurs on the side of the overriding plate and a forearc basin forms toward the subducted plate side. Petrology and geochemistry of boninite series volcanic. The sample from core 2101277a1w is from an isolated piece of basalt flow 4. Ancient oceanic crusts 1 ga are isotopically too depleted to meet the required values of most oib. The similarity of rare earth element patterns in basalt from ocean ridges, backarc basins, some young island arcs, and some continental flood basalts illustrates the dangers of. An outer, inactive arc contains a cretaceouslower tertiary sequence of tholeiitic, calcalkaline and shoshonitic basalts. Their majorelement compositions are similar to both normalmidoceanridgebasalts nmorb and backarcbasalts. Consideration of petrology, geochemistry, and mineral physics suggests that ancient subducted oceanic crusts cannot be the source materials supplying ocean island basalts oib. Asimow geological and planetary sciences, california institute of technology, pasadena, california 91125, usa.
The compositions of materials erupted at these locations, dominantly midocean ridge basalts morbs, have profound implications for the inner workings of the earths mantle, the construction of oceanic crust, and global plate tectonics. To address geochemical analysis on a basin scale, petromod petroleum systems modeling software lets you assess source rock maturity, hydrocarbon migration, and the associated properties of oil and gas. Recently, sheth considered several logratio and discriminantanalysis based diagrams to evaluate and classify the basalts into oib, island arc basalts iab and morb. Mineralogy, geochemistry and petrogenesis of kurile island. Siletzia is a massive formation of early to middle eocene epoch marine basalts and interbedded sediments in the forearc of the cascadia subduction zone, on the west coast of north america. A suite of alkaliolivine to tholefitic basalts, newly dredged from the tasmantid seamounts, are possible primary and nearprimary compositions e. These are variations in source lithology, source volatile. Other data sources and symbols are the same as in figure 4. Basalt and sediment geochemistry and magma petrogenesis in a. D feo is the bulk distribution coefficient for feo, which is the weight % of peridotite kr.
Average composition of basic magmas and mantle sources of island. Mgo l is the weight % mgo content of the liquid, and 38. Mantle plumeswhich are usually, but not always, chemically distinct from the midocean ridge basalt morbmay be rooted in the coremantle boundary and begin with large voluminous heads triggering massive eruptions or be headless and arise in the midmantle. Incompatible element geochemistry in the vanuatu arc parent magmas is dominated by the. It forms the basement rock under western oregon and washington and the southern tip of vancouver island. The lesser antilles system is a typical island arc system hawkesworth and powell, 1980. Melting of oceanic crusts cannot produce highmagnesian oib lavas. Potential origins include eruption at a spreading center before subduction began or eruption. The skidder basalt, which outcrops in an area of central newfoundland immediately to the northwest of red indian lake and approximately 12 km southwest of the town of buchans, is a spilitized, tholeiitic, subalkaline assemblage composed mainly of mafic yariolitic and nonvariolitic pillow lava, mafic pillow breccia and massive mafic flows.
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