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orthopyroxene.htm   (Site not responding. Last check: 2007-10-19) Orthopyroxenes are relatively widespread as a primary mineral in gabbroic and ultramafic rocks where they form with augite, olivine and plagioclase. IRON COUNTY: Orthopyroxene is common in the gabbros and troctolites of the East Mellen Complex as described by Tabet and Mangham (1978). LINCOLN COUNTY: Coarse, lustrous cleavable orthopyroxene occurs serpentinized olivine, magnetite and minor plagioclase in outcrops of peridotite in the bed of the Wisconsin River, near the confluence with the Copper River. www.uwrf.edu /~william.s.cordua/orthopyroxene.htm   (441 words)

CHEMICAL COMPOSITIONS OF CLINOPYROXENE, ORTHOPYROXENE, AND AMPHIBOLE FROM THE HIGH-TEMPERATURE MICROSCOPIC VEINS AND ... In this section, we compare the chemical compositions of mafic silicates (clinopyroxene, orthopyroxene, and amphibole) from the high-temperature microscopic veins and the related textures. Orthopyroxene is a subordinate mineral in the olivine gabbros, occurring as magmatic rims on cumulus grains of olivine and as blebs in intergrowths with brown amphibole in clinopyroxene grains both near the high-temperature microscopic veins and within the interfingering textures. Based on textures, orthopyroxene can be divided into four categories: magmatic rims, blebs in the interfingering clinopyroxene, blebs near the high-temperature microscopic veins, and filling high-temperature microscopic veins penetrating olivine grains. www-odp.tamu.edu /publications/176_SR/chap_04/c4_7.htm   (795 words)

Diogenites Orthopyroxene commonly exhibits fine deformation lamellae that are parallel to the [001] zone axis. Large orthopyroxene oikocrysts (up to 8 mm in longest dimension) surround smaller orthopyroxene grains of similar composition that have long axis deviations from the oikocryst orientation axis. Grain boundaries of all orthopyroxene grains are scalloped to serrated. www4.nau.edu /meteorite/Meteorite/Diogenite.html   (1169 words)

GUIDE TO THE BJERKREIM - SOKNDAL INTRUSION   (Site not responding. Last check: 2007-10-19) Cumulus olivine is not always visible in the poC; it is commonly replaced by orthopyroxene (due to reaction with intercumulus melt) or fine-grained, symplectitic intergrowths of orthopyroxene and magnetite (due to subsolidus oxidation). Note the thicker sequence of zone a cumulates in the axial region of the intrusion at Eptelandsvatnet compared the equivalent in the southern flank (at Hågåsen), and the lack of zone b (poC) at Teksetjørni in the eastern flank of the intrusion. Orthopyroxene (and to a lesser degree plagioclase) near the base of the overlying leuconorite returns to compositions similar to those in the upper part of MCU II, and it exhibits a slight but consistent cryptic regression through the leuconorite into the phiC. www.uib.no /People/ngebr/BKSKFIELDGUIDE.htm   (4283 words)

SAMPLE DESIGNATION: Well LF-48, depth 8089 ft (2465   (Site not responding. Last check: 2007-10-19) Phenocrysts comprise quartz, orthoclase and microperthite, oligoclase, biotite, and orthopyroxene. Orthopyroxene phenocrysts (up to 2 mm in maximum dimensions) are lath-like to highly irregular, the former tending to be elongate, with a typical aspect ratio of 4:1. The estimated primary mineral composition of this granite porphyry is as follows: quartz – 38% oligoclase 27%; potassium feldspar 30 %; orthopyroxene – 2%; biotite – 2%; ilmenite – 1%; apatite and zircon – trace. oro.ess.ucla.edu /labdata/geysers/lf-48-8089.html   (799 words)

st robert poster.doc Texturally the sample is characterized by approximately 30 % chondrules of varying textures (mainly barred or porphyritic) in a matrix of chondrule fragments and native iron. The chondrules are composed mainly of olivine and orthopyroxene, in a matrix of extremely fine grained (average grain size less than 5 microns) recrystallized glass. Temperatures calculated for co-existing orthopyroxene and clinopyroxene are in excess of 1000 °C suggesting that clinopyroxene has not re-equilibrated. castaing.eps.mcgill.ca /meteoriteposter/poster.html   (1399 words)

[No title]   (Site not responding. Last check: 2007-10-19) Enstatite, hypersthene, and ferrosilite are members of the orthopyroxene solid solution series. All have low birefringence (first order red maximum), parallel extinction, and pyroxene 87 degree cleavage. Orthopyroxene occurs with clinopyroxene in many igneous rocks, such as gabbro, diorite, basalt, andesite, and the peridotite family. sorrel.humboldt.edu /~jdl1/web.page.images/orthopyroxene1.html   (92 words)

Trip 2: Road Log and Stop Descriptions 4) composed of 20 to 25 percent orthoclase, 60 to 65 percent plagioclase, and 12 to 15 percent quartz with 5 to 7 percent orthopyroxene and 2 to 4 percent biotite. The rock is composed of 22 to 57 percent alkali feldspar microperthite (chiefly microcline), 10 to 37 percent plagioclase, and 11 to 49 percent quartz with <1 to 14 percent orthopyroxene, 0 to 11 percent amphibole, and rare clinopyroxene. The Yfpg pluton is composed of light-gray, medium- to coarse-grained, inequigranular, strongly foliated monzogranite (farsundite) composed of 30 to 40 percent microcline, 30 to 40 percent plagioclase, and 15 to 20 percent quartz with 5 to 7 percent orthopyroxene, 0 to 2 percent amphibole, 0 to 5 percent biotite, and rare garnet. pubs.usgs.gov /circ/2004/1264/html/trip2/log.html   (10109 words)

Enstatite - Wikipedia, the free encyclopedia Isolated crystals are rare, but orthopyroxene is an essential constituent of various types of igneous rocks and metamorphic rocks. Orthopyroxene is an important constituent of some metamorphic rocks such as granulite. Large crystals, a foot in length and mostly altered to steatite, were found in 1874 in the apatite veins traversing mica-schist and hornblende-schist at the apatite mine of Kjorrestad, near Brevig in southern Norway. en.wikipedia.org /wiki/Enstatite   (539 words)

[No title] Orthopyroxene altered to celadonite and smectite plus an iron oxide mineral (brown). Plagioclase 5 0.5-1.0 mm Clinopyroxene 8 2.5-5.0 mm Orthopyroxene 5 0.5-1.0 mm Intersertal. All clasts are clinopyroxene >/= orthopyroxene >/= plagioclase, similar to those at the base of section 1. www.ngdc.noaa.gov /mgg/geology/odp/data/126/793B/fharvi.txt   (893 words)

template for two-page abstracts in Word 97 (PC) Orthopyroxene samples incubated with SRB demonstrated extensive biofilm development and the precipitation of a brown calcium-rich phase containing phosphate (Figure 4). Additionally, etching of the surface occurred on the orthopyroxene chips (Figure 5) as compared to the angular, ridged appearance in the controls. The crystalline structure of the orthopyroxene was modified into a hummocky morphology that closely resembles the weathering textures that Wentworth et al. www.cas.usf.edu /~jryan/LPSCabstract.html   (649 words)

Petrology of Peridotite and Pyroxenite Xenoliths from the Jericho Kimberlite: Implications for the Thermal State of the ...   (Site not responding. Last check: 2007-10-19) Compositions of orthopyroxene plotted as wt % Cr vs CaO for: 1, spinel-garnet coarse peridotite; 2, garnet coarse peridotite; 3, porphyroclastic non-disrupted peridotite; 4, porphyroclastic disrupted peridotite; 5, megacrystalline pyroxenites; 6, megacrysts. Orthopyroxene grains are homogeneous and similar in composition regardless of habits and textural origin. The clinopyroxene occurs as a fine-grained coating along orthopyroxene grain boundaries in peridotite xenoliths recovered from the Jericho pipe as well as from the Grizzly pipe (Boyd and Canil, 1997). library.iem.ac.ru /j-petr/1-4099/html/egc006_gml.html   (10923 words)

PSRD:: Carbonates in ALH 84001: Part of the Story of Water on Mars The orthopyroxene is accompanied by some chromite, feldspathic glass, augite, apatite and olivine. As the magma crystallized, orthopyroxene accumulated in the magma. Carbonates found in the interstices of orthopyroxene surrounding the secondary mineral regions are similar in appearance to those found entrained within feldspathic glasses. www.psrd.hawaii.edu /July04/carbonatesALH84001.html   (4254 words)

NWA 2200 Lunar Meteorite Clinopyroxene and orthopyroxene grains in mineral and lithic clasts have Fe/(Fe+Mg) = 0.258 to 0.482, and 19 of 23 analyses have Ti/(Ti+Cr) = 0.53-0.75. FeO/MnO ratios measured for olivine (99.7, 105.5), clinopyroxene (73.7) and orthopyroxene (65.4) are unmistakably within the ranges for these minerals in known lunar rocks. Feldspar grains in mineral and lithic clasts have a narrow compositional range of An The combination of anorthitic plagioclase and ferroan mafic silicates suggests that the majority of the material in this specimen was derived from FAN-suite lithologies (Kuehner et al., 2005). www.catchafallingstar.com /nwa2200.htm   (241 words)

Antarctic Meteorite Newsletter 26,2 - Petrographic Descriptions Olivine ranges in composition from Fa, with a clustering of compositions around Fa Orthopyroxene is Fs The meteorite is a CO3 chondrite of moderately high subtype (estimated 3.6) and is almost certainly paired with MET 00694 and MET 00737. The mineral compositions are homogenous; olivine is Fa and orthopyroxene is Fs The meteorite is an L5 impact-melt breccia. Pyroxene grains are mixtures of orthopyroxene and augite with exsolution lamellae of 1-5 microns. www-curator.jsc.nasa.gov /antmet/amn/amnaug03/petdes.htm   (2126 words)

Metamorphic rocks - Metamorphic Facies   (Site not responding. Last check: 2007-10-19) The presence of orthopyroxene in metabasic rocks is diagnostic of this and the pyroxene hornfels facies. Otherwise known as the glaucophane-lawsonite schist facies, these rocks are almost entirely restricted to Mesozoic and Tertiary orogenic belts such as the circum-Pacific belts and the Alpine-Himalayan chain. Rarely found, as the extremely high temperatures required are only achieved at direct contacts with flowing basic magma, or in completely-immersed xenoliths. teachserv.earth.ox.ac.uk /courses/es2-metrock/1metfac.html   (897 words)

Martian Meteorites Large, prismatic orthopyroxene phenocrysts exhibit preferred orientation suggestive of magmatic flow and/or crystal accumulation, possibly in a subsurface dike; olivine phenocrysts are weakly oriented and tend to occur in clusters. showing olivine phenocrysts (yellow-brown) and smaller, prismatic orthopyroxene phenocrysts (pale brown) in a finer grained groundmass of mainly pigeonite (pale brown) and maskelynite (white). Several orthopyroxene phenocrysts are visible as prismatic grains with prominent twinning. www4.nau.edu /meteorite/Meteorite/Martian.html   (1676 words)

Mineral Description The similar appearence in plane light of orthopyroxene and clinopyroxene are highlighted in this image. The low interference colours characteristic of orthopyroxene compared to clinopyroxene are evident in this image. the effects of the substituion of Fe for Mg in orthopyroxene on the optical properties is evident in examining Figure 13.4 in Nesse. www.brocku.ca /earthsciences/people/gfinn/minerals/opx.htm   (215 words)

singleX Orthopyroxene [(Fex, Mg1-x)SiO3], an orthosilicate solid solution between ferrosilite [FeSiO3] and enstatite [MgSiO3] is, after olivine (Belley et al., in preparation), the second major constituent in the upper mantle. Orthopyroxene magnetic properties vary not only with chemical composition and temperature but also with measurement orientation. Natural orthopyroxenes and other silicate crystals display ferromagnetic behavior at room temperature due to the presence of magnetite micro-inclusions (e.g., Lagroix and Borradaile, 2000). www.science.siu.edu /geology/people/ferre/France/resfrance/singleX.html   (901 words)

PSR Discoveries: Hot Idea: Life on Mars Orthopyroxene makes up about 95% of the rock, and the large size of the crystals suggests that the rock crystallized in a slowly-cooling magma body inside the Martian crust. Green is orthopyroxene (the silicate with iron and magnesium), blue is glassy plagioclase feldspar, and the various shades of red and orange are carbonate minerals with a range in chemical composition. Its high abundance of one mineral (orthopyroxene) indicates that this mineral must have accumulated in the magma, probably near the bottom of the magma body, eventually forming the original igneous rock with large crystals of orthopyroxene. www.psrd.hawaii.edu /Oct96/TheRock.html   (906 words)

[No title]   (Site not responding. Last check: 2007-10-19) Partial melting is thought to change 'undepleted' or 'fertile' mantle material to depleted mantle typical of the upper mantle, which is consequently known as the 'depleted' layer. The residue after melting is enriched in olivine and chromite, and is composed of olivine, orthopyroxene, and chromite (harzburgite). If all the orthopyroxene melts, the residue will be composed of olivine and chromite and is known as dunite.Dunite is the host for many economic deposits of chromite. instruct.uwo.ca /earth-sci/200a-001/mantle.htm   (367 words)

[No title]   (Site not responding. Last check: 2007-10-19) A84 is dominated by nearly homogeneous cumulus orthopyroxene, and minor chromite found within cumulus orthopyroxene grains and interstitial areas [1]. Similar assemblages of olivine, chromite and orthopyroxene can be found in other martian meteorites, such as the nearly identical shergottites LEW 88516 and ALH 77005 (L&A) and the lithology A megacryst assemblage of EETA 79001 (EET-A)[1, 3-6]. Although complex scenarios of mixing or assimilation are required to account for the varying observed trace-element and isotopic compositions for these rocks, the possible parental similarities suggest that a generic brand of Al-poor basaltic magma was (or is) globally prevalent on Mars [7,9]. www.lpi.usra.edu /lpi/meteorites/harm94.html   (514 words)

Union College Geology Department, Petrology page, lunar rocks and lunar thin sections, thin section images, shocked ... Here, highly fractured orthopyroxene is visible, as is plagioclase that has abundant exsolved oxide dust. The glass in the vein is isotropic, and so is the maskelynite that is particularly abundant near the orthopyroxene grains around the margin. The polygonized orthopyroxene (shattered with different domains rotated in different directions) are clearly visible. www.union.edu /PUBLIC/GEODEPT/COURSES/petrology/moon_rocks/78235.htm   (296 words)

meteorite minerals Pyroxenes --A group of mostly dark colored rock-forming minerals common on Earth and in meteorites. Orthopyroxenes are a subcatagory that are found in meteorites--particularly chondrites and achondrites. Orthoferrosilite --FeSiO3--This is the other orthopyroxene end member. earthsci.org /fossils/space/craters/met/mineral.htm   (1051 words)

8th INTERNATIONAL KIMBERLITE CONFERENCE (8IKC) Some coarse Louwrencia peridotites are relatively rich in orthopyroxene with modal values ranging to 39.5 wt % in contrast to 44.1 wt % for the Kaapvaal. To bypass such uncertainties, large orthopyroxene and olivine crystals of representative samples have been studied in detail to ascertain the degree of modification suffered through metasomatism. The orthopyroxene solvus provides a typical example of such results as CMS reversed overlapping data are best described through a symmetric orthopyroxene – asymmetric clinopyroxene model with excess parameters limited to entropic contributions unlike those postulated so far. www.venuewest.com /8IKC/s6oral.htm   (4352 words)

NWA 2046 This sample is very distinctive in containing large crystals of both olivine and orthopyroxene which exhibit a preferred alignment, probably as a result of crystal growth and transport by flow within a magma conduit beneath the surface of Mars. Image 3: Thin section image (width 5 mm) in cross-polarized light of NWA 2046 showing olivine phenocrysts (green with dark brown mantles) and two parallel prismatic orthopyroxene phenocrysts (pale yellow, at lower left and right) in a finer grained groundmass of twinned pigeonite (blue, magenta and yellow), maskelynite (fl) and opaque oxides. Image 5: False-color backscattered electron image of NWA 2046 showing prismatic orthopyroxene phenocryst and microphenocrysts (blue) mantled by pigeonite (green), with groundmass pigeonite (orange and yellow), olivine (white), maskelynite (fl), chromite and ilmenite (both white). www2.jpl.nasa.gov /snc/nwa2046.html   (792 words)

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