 | | Journal (article/letter/editorial) | | Petrology of the Western Reykjanes Peninsula, Iceland by S. P. JAKOBSSON 1 , J. JONSSON 2 ,artrf F. SHIDO...picrite basalts exhibit a primitive mineralogy with chromite, olivine (Fo 89) and plagioclase (An 90) as phenocrysts... T w o main features of the Recent basalts of Iceland are first, the active volcanic belts can be divided...tholeiitic zones reaches a maximum range in central Iceland. The variation has been demonstrated for the submarine...the Holocene and late Quaternary tholeiites of Iceland (Sigvaldason et al., 1974). A number of papers |  | | Journal (article/letter/editorial) | | Jorullo, Mexico, (2) an olivine tholeiite from Iceland, and (3) an "olivine boninite" from a marginal...occurs at 1,272~ C with the appearance of spinel (chromite); olivine appears at 1,260 ~ C. Plagioclase precipitates...concentration was neglected at the onset The Thingmuli lavas of basaltic andesite and icelandite composition...rate oc (D/RT)A volcanic centers is Thingmuli in Eastern Iceland (Carmichael 1964a, 1967a). The lavas...available on the mineralogy and petrology of the Thingmuli lavas, we have chosen the most "primitive" representative |  | | Journal (article/letter/editorial) | | 196? THE MINERALOGY OF THINGMULI, A TERTIARY VOLCANO IN EASTERN ICELAND IaN S. E. Canlrrcn.r.or-,...which make up a Tertiary central volcano in eastern Iceland have been examined mineralogically with the...types forming part of one of these volcanoes, Thingmuli, are olivine-tholeiite, olivine-free tholeiite...sensitivity, 0 02/e. are infrequently found at Thingmuli, but only one of these rocks, a picrite-basalt(No...details of the petrography or chemistry of the Thingmuli series are given here.the readerbeing referredto |  | | Journal (article/letter/editorial) | | The Petrology of Thingmuli, a Tertiary Volcano in Eastern Iceland by I. S. E. CARMICHAEL Department of...of Tertiary flood-basalts so prominent in eastern Iceland has been interrupted from time to time by central...1959) there is one of these central volcanoes (Thingmuli), and like the Breiddalur volcano to the south-east...enveloping flood-basalts. The main lava-types found at Thingmuli are olivine-tholeiite, olivine-free tholeiite...lava types. The. relatively infrequent groups of ICELAND 1 Present address: Department of Geology and Geophysics |  | | Journal (article/letter/editorial) | | Tertiary Lavas of Eastern Iceland and their Significance with respect to the Iceland Geochemical Anomaly...sciences demonstrating the anomalous nature of Iceland with respect to the surrounding mid-ocean rift...wider spectrum of basalt compositions exist in the Iceland area in comparison to the rest of the Mid-Atlantic...isotopes of Sr and Pb are particularly abundant in Iceland (Schilling, 1973; Hart et al., 1973; Sun et al... A. WOOD GEOLOGICAL SUMMARY OF EASTERN ICELAND The eastern Iceland lava pile has an approximate stratigraphic |  | | Journal (article/letter/editorial) | | unzoned Fo68 olivine and less abundant subhedral chromite (which is also present as crystalline inclusions...pyroxenes (augite, pigeonite, and orthopyroxene), chromite, analbite glass, and apatite are found interstitial...forsterite (Mg), ilmenite (Fe, Ti), rhodonite (Mn), chromite (Cr), apatite (P), and magnesium fluoride (F)...they likely postdate accumulation of olivine and chromite. They appear to have crystallized in the sequence...and deserve mention: Ti-biotite, pigeonite, and chromite. Titanium-rich biotite is common in a variety |  | | Journal (article/letter/editorial) | | standard for all elements except Cr, for which chromite was used. Corrections were made for drift and...Carmichael (1967) for tholeiitic basalts of Thingmuli, Iceland, province (Fig. 6b). Note that Wo content... S - - S ' (Brown and Vincent, 1963) and Thingmuli, Iceland, T - - T ' (Carmichael, 1967) provinces....Quaternary basanites and tephrites of the Lake Rudolf region, Kenya (Brown and Carmichael, 1969), and olivine...have low Wo contents and fall into the nonalkalie region of the diagram, and those in nephelinic rocks have |  | | Journal (article/letter/editorial) | | Total iron K-orthocLase, as l4n-tephroite, Cr-chromite, Feo. tion and temperatures. The above results...Standards: Mg, Fe, Ti (Ilmenite K-13-131-8), Al, Cr (Chromite), Mn (Tephroite), as in Anderson (1968). Corrected... Anderson, 1968), G146, G99 (basalts Thingmuli voleano, Iceland, Carrrichael, 1967), L921 (surnmit lava...Anderson,unpublished data) and lavas of Thingmuli volcano,Iceland (Carmichael,1967),containmore reduced...the lower oxygenfugacitiesof the Hat Creek and Thingmuli basaltsreflect a more reducedmantle environment |  | Coleman, R.G., Hadley, D.G., Fleck, R.J., Hedge, C.T., Donato, M.M. (1978) The Miocene Tihama Asir ophiolite and its bearing on the Red Sea opening. Precambrian Research, 6 (1) doi:10.1016/0301-9268(78)90071-2 | Journal (article/letter/editorial) | | fractionation in much the same manner as lavas at Thingmuli Volcano, Iceland. Late Miocene tilting of the sedimentary...the peridotite with discordant bodies of dunite. Chromite bodies occur at the top and in these dunites. |  | Coleman, R.G., Huston, C., El-Boushi, I.M., Al-Hinai, K.M., Bailey, E.H. (1978) Occurrence of copper-bearing massive sulphides in the Semail Ophiolite, sultanate of Oman. Precambrian Research, 6 (1) doi:10.1016/0301-9268(78)90072-4 | Journal (article/letter/editorial) | | fractionation in much the same manner as lavas at Thingmuli Volcano, Iceland. Late Miocene tilting of the sedimentary...the peridotite with discordant bodies of dunite. Chromite bodies occur at the top and in these dunites. |  | NEKVASIL, Hanna, McCUBBIN, Francis M., HARRINGTON, Andrea, ELARDO, Stephen, LINDSLEY, Donald H. (2009) Linking the Chassigny meteorite and the Martian surface rock Backstay: Insights into igneous crustal differentiation processes on Mars. Meteoritics & Planetary Science, 44 (6) 853-869 doi:10.1111/j.1945-5100.2009.tb00773.x | Journal (article/letter/editorial) | | (that is, reflect the composition of the source region), or represent compositions modified by secondary...meteorite is a dunite with cumulus Fo68 olivine and chromite with interstitial pyroxenes, apatite, maskelynite...Ti-biotite, maskelynite, alkali maskelynite, apatite, chromite, and additional minor phases (e.g., Floran et...1.1 1.3 25.1 27.6 0.5 0.1 0 0 Symbols: Chr-chromite; Ol-olivine; Pig-pigeonite; Aug-augite; Opx-orthopyroxene;...indicate the compositions of the phases of Table 2. Chromite and olivine are the phases found at the highest |  | | Journal (article/letter/editorial) | | stabilization of Cr-bearing phases (spinel or chromite at low pressure), which severely limits the enrichment...Helena Na2O+ K2O wt% melt 12 10 8 Critical line Thingmuli 6 4 2 0 40 Hawaiian tholeiites 45 50 55 60...(1969). The second corresponds to the Thingmuli series in Iceland studied by Carmichael (1964, 1967), representative...content of olivines from the olivine tholeiites of Thingmuli are, similarly to the Hawaiian basalts, in the...0.4 wt%. For the most dierentiated rocks of Thingmuli, the model however, predicts a slight decrease |  | Waters, L E, Cottrell, E, Coombs, M L, Kelley, K A (2021) Generation of Calc-Alkaline Magmas during Crystallization at High Oxygen Fugacity: An Experimental and Petrologic Study of Tephras from Buldir Volcano, Western Aleutian Arc, Alaska, USA. Journal of Petrology, 62 (3) doi:10.1093/petrology/egaa104 | Journal (article/letter/editorial) | | Absorption Near Edge Structure (XANES) spectroscopy. Chromite is the liquidus phase, followed by olivine, then...saturation of spinel as a liquidus phase (initially as chromite) and continuous crystallization through the experimental...liquids that included chromium did crystallize chromite (>24 wt% Cr2O3 and >12 wt% FeO) as a near-liquidus...2) crystallized chromite olivine plagioclase clinopyroxene magnetite (chromite-out) hornblende...small (<50µm) crystals in the groundmass. Spinel (chromite and magnetite) occurs in all samples (tabulated |  | | Journal (article/letter/editorial) | | well-studied igneous bodies: the Bishop Tuff, Thingmuli Volcano, and the SkaergaardIntrusion. The Fe-Ti...possibly within the tuffafter eruption. Thingmuli Volcano in Iceland contains severalrock types that have...contrast, tholeiitic volcanic rocks, as typified by Thingmuli, crystallized at much lower f, (generally about...augite,pigeonite,and olivine for sampleHl28 from Thingmuli(Carmichaet,1967a), projectedusingPXPROJ.The average...enclosed Thingmuli in quartz was protected from reequilibration when its The lavas of Thingmuli, a Tertiary |  | | Journal (article/letter/editorial) | | crystallisation of olivine, clinopyroxene and/or chromite. Penguin lavas have higher 87Sr/86Sr(0.7039) and...of diopsidic augite-salite composition 0-10%. Chromite occurs both as small crystals contained in olivine...1971) and not unlike the magnesian portion of the Thingmuli trend (Carmichael, 1964). (b) Bridgeman Island...(b) Penguin Island. Small microphenocrysts of chromite are present as intergranular crystals or as inclusions...Island lisation of olivine, clinopyroxene and/or chromite. Thus Penguin basalts are characterised by steep |  | | Journal (article/letter/editorial) | | Basaltic Glasses from Iceland P. Thy Nordic Volcanological Institute, University of Iceland, IS-101 Reykjavik...Reykjavik, Iceland Abstract. Crystallization of spinel minerals in transitional and alkali basalts from Iceland...natural rocks were studied. Alkali Basalts in Iceland Classification of Icelandic basalts is generally...and petrology of the active volcanic zones of Iceland has been reviewed by Jakobsson (1972, 1979) and...liquid in transitional and alkali basalts from Iceland. In order to Present address: Department of Geology |  | | Report (issue) | | the Stillwater Complex with Hawaiian basalt. Thingmuli basalt, oceanic tholeiitic basalt, and alkali...clinopyroxene, inverted pigeonite, plagioclase, or chromite; noncumulate igneous rocks with ophitic, subophitic...Casella (1969) gave summaries of the chromite, olivine+chromite, olivine+bronzite, and bronzite; geology...geology of the encircling Beartooth Mountain region. Figure at least 15 cycles are recognized in the Peridotite...geology within the Stillwater and 13 contain chromite and chromite+olivine cumulates Complex compiled from |  | | Journal (article/letter/editorial) | | abundances, depletion in LREE and flattening in the HREE region. The close similarities between the Troodos and...often containing microphenocrysts of octahedral chromite. Phenocrysts of Ca-poor pyroxene occur in some...phenocrysts of olivine and Ca-rich pyroxene, and chromite microphenocrysts. The sample described by J6rgensen...endiopside (En4s_ssFST_tlWo3s__44). The spinel is a chromite with a low ulvSspinel-magnetite component. At...phenocryst assemblage lacks plagioclase. Substituting chromite for plagioclase is in accordance with the observed |  | | Journal (article/letter/editorial) | | Lower Tertiary plateau basalts of the Scoresby Sund region, East Greenland Lotte Melchior Larsen, W. Stuart...Lower Tertiary plateau basalts of the Scoresby Sund region, East Greenland Lotte Melchior Larsen, W. Stuart...sea-tloor spreading in the North Atlantic. In the region stretching from Scoresby Sund southward to 69°N...canic episode from sites in the NW part of the region; the Rømer Fjord and Skrænterne Formations form...have microphenocrysts of olivine (F090-70) and chromite, while the main basalts comprise both aphyric |  | | Journal (article/letter/editorial) | | contents and by their location in a non-orogenic region. The rock types in which pyroxenes were analyzed...for all elements excepts Cr, for which a natural chromite was used, and corrections were made for deadtime...andesite to quartz latite series in the San Juan region of Colorado. The available data on clinopyroxenes...Carmichael, The mineralogy of Thingmuli, a Tertiary volcano in eastern Iceland, Am. Mineralogist 52 (tr967)...from the Tertiary volcanic rocks of the San Juan region, Colorado, Am. Mineralogist 21 (1936) 679. [18] |  | | Journal (article/letter/editorial) | | of common igneous minerals such as olivine and chromite (e.g. Brügmann et al., 1987; Hart & Ravizza,...provided in the basalt to rhyolite sequences in Iceland (e.g. Carmichael et al., 1974; Wood, 1978) and...assimilated sediment or altered oceanic crust (e.g. Iceland, Hemond et al., 1988)— these sequences are more...1), using natural standards (magnetite, rutile, chromite, diopside), 15 kV accelerating potential and 20...other oceanic fractionation sequences such as Iceland (Carmichael, 1964)] suggests that magnetite is |  | | Journal (article/letter/editorial) | | icelandites from Thingmuli volcano, Iceland, and as reported by Scowen et al. (1991) for chromite in Kilauea...(1967b) The mineralogy of Thingmuli, a Tertiary volcano in eastern Iceland. Am Mineral 52: 1815–1841...of abyssal lavas recovered by DSRV Alvin from Eastern Galapagos Rift and Ecuador Rift. 3. Trace element... Roeder PL, Helz RT (1991) Reequilibration of chromite within Kilauea Iki lava lake, Hawaii. Contrib |  | | Journal (article/letter/editorial) | | PLAG = plagioclase, OPX = orthopyroxene, CRM = chromite, MT = magnetite, QTZ = quartz. Olivine clinopyroxenite...crystallized after, and in reaction with, both chromite-bearing olivine and clinopyroxene (Fig. 1, Table...in diameter, with olivine up to 1 cm in length. Chromite (Table 2A, 2-3), is 0-05 to 0-10 mm in diameter...the olivine-bearing gabbro, magnetite replaces chromite as the liquidus phase in more evolved melts crystallizing...assemblages are compositionally similar to the chromite, olivine and clinopyroxene found in the ultramafic |  | | Journal (article/letter/editorial) | | iron-rich pleonaste (M=60.2) with significant chromite solid solution (Table 1, No. 4). The Spring Mount...alkaline basaltic volcanic provinces of north-eastern New South Wales (Wilshire and Binns, 1961; Binns...(rag= 79). Inter- mediate members from north-eastern New South Wales include three altered but originally...(picritic) partial melts within the peridotitic source region (cf. Wilkinson, 1976). Dunites and harzburgites...inhomogeneity characterizing the upper mantle source region of basaltic magmas. The following discussion of |  | | Journal (article/letter/editorial) | | is size average. from 90 Takashi aluminous chromite to chromian pleonaste with the increase of fayalite...and hypersthenic rock series in the Izu-Hakone region (Kuno, 1950). The Oura femic minerals of calculated...relatively to those and Stillwater weak iron region the liquids same The MgO/(MgO +‡”FeO) (Table... St=Stillwater Th=Thingmuli variation the and liquid pigeonitic rock region (Kuno, with SiOg ...Critical ( lower 60 %) ( Hess, HB0ln 1968 ). region and Main zone ( lower respectively, melt we |
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