Petrographic Data Files. been done on monazite grains, using polished thin sections, to determine the age and to inter pret them in conjunction with the textural rela tionship of minerals. Introduction The Vredefort impact structure is amongst the largest impact basins known on Earth. (2) Many monazite grains are spatially associated with biotite coronas around garnets, formed … Carbonate-hydroxylapatite is also present; the significant carbonate component is inferred and estimated from the low analytical total and from the necessity to charge balance the substantial Na content. to the monazite location in the thin section in order to evaluate the textural and zoning significance ..... 13 6: Schematic and yttrium x-ray map showing the three compositional zones and associated dates for a monazite grain in the restite.. ..... 17 7: Monazite date results from the restite layer..... 17 8: Restite monazite composition vs calculated date. 3c, d) are largely replaced. The fibrolite knot is oriented parallel to S North Tincroft Lode (New Cook's Kitchen Mine) forms a segment of an ENE-WSW-striking lode structure that can be traced for —2 km along strike and —800 m vertically through the Camborne-Redruth mining district. The same oper-ating conditions were used to generate all monazite maps and therefore relative concentrations of Ce, Th and Y are assessable between grains in the same sample and between samples. Monazite is a rare phosphate mineral with a chemical composition of (Ce,La,Nd,Th)(PO 4,SiO 4). Interestingly, despite the notable Cl content of … Monazite is a common accessory mineral in various metamorphic and magmatic rocks, and is widely used for U–Pb geochronology. 2) or, for example, located near a quartz-filled crack within a tourmaline (Fig. It is very difficult to obtain any specimens of this incredibly beautiful and rare phosphate, especially in crystals from Bolivia like this. One of the two most important aspect of this work is that (1) monazite selection for isotopic analysis is based on the petrographical setting (i.e. Monazite identification was facilitated by Ce X-ray mapping of full thin sections and by QEMSCAN mapping. Location of monazite in thin-sections is not easy under the optical microscope, because although all the high-relief accessory minerals are readily located, it is difficult to distinguish monazite from zircon or xenotime (Montel, 1993). However, linking monazite U–Pb ages with the PT evolution of the rock is not always straightforward. Our new EPMA was installed in March 2016, and is tailored for … Dolomite in Thin Section. It usually occurs in small isolated … sjöstrand and thin sections have been made from rock samples to study the mineral. Cambro–Ordovician monazite inclusions in Cine and Central Menderes Massif garnets are ~450 m.y. ..... 19 9: A) BSE images of the leucosome (16TG-143-5) … The three minerals are monazite-(Ce), monazite-(La) and monazite-(Nd). (2002) determined chemical ages of monazites that were first optically examined in thin section, thus still preserving full textural context of the analysis, but were then removed from the thin sections by drilling with a diamond microdrill. Monazite is usually found in granitic pegmatites, but these crystals are found in hydrothermal tin veins where is an absolute absence of Thorium (usually a trace element in Monazite). Ilmenite most often contains … We specialise in precise, accurate, high spatial resolution, uranium-thorium-lead geochronology of zircon, monazite, xenotime, titanite, allanite, … Consequently, concentrations of Ce, Th and Y in monazite are described below as ‘low’, ‘average’ and/or ‘high’. In situ petrographic thin section U–Pb dating of zircon, monazite, and titanite using laser ablation–MC–ICP-MS In situ U–Pb dating of monazite and zircon within pet-rographic thin section by LA–MC–ICP-MS has been previously conducted[e.g.,Refs.10,11];however,inbothstudiesthegrains were ablated in ‘raster’ mode with typical sampling volumes of 80 m×18 m×5 m [10] or 60 m×60 m×15 m [11]. monazite at 1 µm resolution with a 1 µm beam and collection times of 35 ms per pixel. Full-section X-ray maps of three sample thin-sections were collected via EPMA to identify all monazite grains. This piece is from the same mine for which this material was discovered along the Contacto … By contrast, monazite grains in the mylonitic matrix (Fig. Monazite in Thin Section. Here, we present an alternative chemical dating method to acquire higher precision age information from monazite grains in thin section, utilising a newly developed XRF-microprobe. orientation of the thin section cut through the crystal (Fig. Calcite in Thin Section. Occurrence: An accessory mineral in granites, syenites, and their pegmatites; in carbonatites and volcanoclastic rocks; in fissure veins and high-grade metamorphic rocks; commonly detrital in river and beach sands; rarely authigenic in shales and intense weathering zones. Monazite response to ultrahigh-pressure subduction from U–Pb dating by laser ablation split stream BradleyR.Hackera,⁎,AndrewR.C.Kylander-Clarka,RobertHoldera,TorgeirB.Andersenb,EmilyM.Petermanc, Emily O. Walshd, Jonathan K. Munnikhuise a Earth Science, University California, Santa Barbara, CA 93106-9630, USA b University of Oslo, Physics of Geological Processes, PO Box 1048, Blindern, 0316 … This work … Monazite-(Ce) at Ritterpass is rarely such intensely orange coloured, but typically contains reddish flakes - 'Victory crystal group' sitting in 'boxwork' (dissolution cavity) of a large allanite-(Ce). section. The size of the fluorapatite zone around the monazite is especially thin when the corona is included in tourmaline, indicating that the monazite is largely preserved (Fig. These minerals were identified by systematic scanning of polished thin sections in an SEM using backscattered electron and energy dispersive X-ray detectors. included in peak metamorphic phases, associated with secondary assemblages, located in the matrix foliation, in pressure shadows…)and that (2) EMP and ID-TIMS data were acquired from the same grains extracted by micro drilling directly from petrographic … Employing such large raster areas on a routine basis limits the versatility of this technique, since many accessory … Mineral Group: Monazite group. The thin section was cut too thin, and the observed birefringence values of the anisotropic minerals are much lower than what one is accustomed to seeing. Monazite sand: Monazite sand with a resinous luster from Malaysia. Colour change from reddish orange in daylight to pinkish brown in tungsten light … Most of the grains are very small Original language: … Monazite geochronology of one thin section revealed two distinct … Keywords: granular zircon; shocked monazite; shock microtwins; pseudotachylite; granophyre 1. Having been deeply eroded during 2020 My of its history, it allows investigation of the impactites at the lowest levels of this large impact structure [1–5]. Apatite in Thin Section. In a companion study, Scherrer et al. Ilmenite - FeTiO 3 Ilmenite is named after the locality of its discovery in the Il'menski Mountains, (Russia). Association: Zircon, xenotime, titanite, thorite, allanite, columbite, wolframite (pegmatites and … Andalusite in Thin Section. Keck Foundation Center for Isotope Geochemistry at the University of California–Los Angeles. It is a titanium-iron oxide mineral with formula FeTiO 3.The ilmenite crystal structure is an ordered derivative of the corundum structure; in corundum all cations are identical but in ilmenite Fe 2+ and Ti 4+ ions occupy alternating layers perpendicular to the trigonal c axis. The dependence of the degree of replacement on the local mineral assemblage … One such lithic clast from the Vredefort … We investigated the behaviour of monazite in a metasedimentary sequence ranging from greenschist facies phyllites into upper amphibolites facies anatectic gneisses, which is … Hornblende) in Thin Section. Twenty-eight grains were mapped at high-spatial resolution (0.3--6.0 mum). However, granophyre (impact melt) dykes in such structures preserve clasts of supracrustal rocks, transported down from the uppermost levels of the initial structure. (c–h) Photomicrographs of samples F122B and S89A from thin sections cut perpendicular to S 1 and parallel to L 1, unless otherwise indicated; for micas, ‘(p)’ denotes prograde, syn-D 1 growth whereas ‘(r)’ denotes retrograde, post-D 1 growth. Monazites in reaction with allanite from the Kuzey Detachment, which bounds the northern edge of the … The Sensitive High Resolution Ion Micro Probe Facility (SHRIMP) are large mass spectrometers that allow in situ isotopic and trace element micro-analysis of complexly zoned minerals in grain mounts and thin section plugs, with a spatial resolution of 5-20 microns. Collected September 20th 2010 by Ate van der Burgt Picture taken with Zeiss V20 (Achromat 1.5x objective), Sony alpha7 mounted on LMscope achromatic adapter, Helicon Pro See: Cuchet, S., Crumbach, M. and van der … Standard 30 µm polished thin sections cut for petrographical analysis were utilized for in-situ monazite Th–U–total Pb dating. Thin section observations coupled with electron microprobe analyses reveal the presence of several REE-bearing minerals: allanite, fergusonite (Ce), fergusonite-(Y), zircon and apatite as accessory minerals, and xenotime-(Y), bastnäsite-(Ce), thorite, monazite-(Ce) and hingganite-(Y) as secondary (hydrothermal) minerals. These are produced by Smith College students as part of an assignment in an introductory petrololgy course. The ages … In both samples, there is a tendency for the monazite rims to yield lower ages than the cores, but the difference cannot be resolved with the present analytical precision. Many have "rollover" images that cross the polarizer when the mouse goes over the image. Thin sections were cut with a high-precision diamond saw or … A catalogue of minerals & textures in thin section Ruth Siddall, University College London Minerals are listed in the order in which they appear in Deer, Howie & Zussman (1992). Hornblende under microscope {part 2} Enjoy the videos and music you love, … The instruments' precision and accuracy are evaluated against high precision isotopic dating by LA-PIMMS (Parrish et al., 1999) , where 208 Pb/ 232 Th ratios corrected for 204 Pb are analysed. The thin sections have been observed using polarization microscopy and two different types of monazite were discovered. We report here, for the first time, the occurrence of hydrothermal monazite and xenotime in alteration haloes associated with the gold-mineralized zones of the Hutti Gold Deposit in Karnataka, India. Chloritoid in Thin Section. It is classed as a member of the feldspathoid group of minerals. Monazite is produced from heavy-mineral concentrates and then separated out by specific gravity, magnetic processes, and other processes. Monazite is named after Greek "monazein" - to be solitary, alluding to its rare occurence as isolated crystals in the mineral's discovery material. To address this, monazite in garnet-bearing rocks from the massif’s Gordes, Central, and Cine sections were dated in thin section (in situ) using the Th–Pb ion microprobe method. However, on the basis of the BSE information the 15 analyses from SGL5 monazite yielded … Mineral … older than matrix grains. With a section on Mineral Analyses By JEROME STONE GEOLOGICAL SURVEY PROFESSIONAL PAPER 568 Prepared on behalf of the U.S. Atomic Energy Commission Occurrences of detrital mona%ite in the western Piedmont of Virginia^ North Carolina^ South Carolina^ and Georgia^ and methods used to appraise them UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1968. Amphibole (var. Although this is a labor-intensive procedure compared to EMP dating, and still cannot be done on very small monazites, an X-ray … Three lines of evidence from schists of the Great Smoky Mountains, NC, indicate that isogradic monazite growth occurred at the staurolite-in isograd at ̃600°C: (1) Monazite is virtually absent below the staurolite-in isograd, but is ubiquitous (several hundred grains per thin section) in staurolite- and kyanite-grade rocks. The age determination of monazite grains with Th-U-Pbsystematics is a reliable and potential geochronological method, which aids in the rapid and precise determina tion of geologic events (Montel et aI., 1996; Suzuki and Adachi., 1991). Talc in Thin Section. From our experi- ence, we suggest the following criteria: (1) a crystal with two pyramids is certainly a zircon, because monazite displays only one pyramid, if any; (2) a crystal with a … (c) Partially resorbed garnet poikiloblast surrounded by biotite, muscovite and fibrolite. The first type appears as small Thin section micro-structures observed show effects of a multistage deformation history with both dynamic and static recrystallization processes. Thin sections 3c and 3b repre-sent a migmatite gneiss with two different phases, mesosome and leucosome. Studying these clasts is the only way to understand the properties of already eroded impactites. Hornblende in XPL. For example, impact-related pseudotachylites, formed at … Zircon in Thin Section. Hornblende in PPL. Cancrinite is a member of the cancrinite-vishnevite family with the formula Ca 2 Na 6 Al 6 O 6 (CO 3) 2 *2H 2 O. Monazite forms tabular or prismatic crystals of yellow, yellow-brown, brown, rose-red, reddish-brown colour. Specimens are sand-grain size particles. Detection and chemical mapping of monazite was conducted using the JEOL JXA8230 electron microprobe (EMP) at AGH University of Science and Technology (Kraków, Poland) with operating conditions of 100 nA, 15 kV and a dwell time of 100 ms. Monazite grains were … UNITED … The comparison … hornblende. The Vredefort impact structure in South Africa is deeply eroded to its lowermost levels. 16). Monazite at low grades Monazite at low grades is often embayed due to either irregularities in growth in different directions, or to In situ Th/Pb geochronological analysis was conducted with a CAMECA IMS 1270 secondary ion mass spectrometer (SIMS) at the W.M. Cancrinite - Ca 2 Na 6 Al 6 O 6 (CO 3) 2 *2H 2 O Found originally in 1839 in the Ural Mountains, it is named after Georg von Cancrin, a Russian minister of finance. 3a, b). Monazite cores are also distinguished by a Th/U ratio below 10, whereas the rims have Th/U of the order of 30–50 (see trace element section, below). Fergusonite and hingganite are identified in this massif for the first time. In situ monazite and xenotime geochronology by electron microprobe analysis (EPMA) at the University of Colorado, Boulder January 16th, 2017 Lab description The CU Boulder Electron Microprobe Laboratory hosts a JEOL JXA-8230 electron probe microanalyzer (EPMA), a carbon and metal evaporator for coating, and a thin section preparation shop. Titanite/Sphene in Thin Section. What is Monazite? Lode samples from previously
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