[B._Beckhoff,_et_al.]_Handbook_of_Practical_X-Ray_(b-ok.org).pdf

G fragments contain fe s filled fractures whilst h

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( g ) fragments contain Fe, S filled fractures, whilst ( h ) Cu–As-mineralization occurs along cross-cutting features. Some elements are enhanced relative to others 2.1-2. Ore genesis: Mn-bearing banded iron formation ( a ) with calcite ( b ) and quartz veinlets ( c ). Pyrite blasts ( d ) are concentrated in two zones with variable grain sizes. Some pyrite grains show elevated Au values ( e ) ( Figure caption contin- ued next page )
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Methodological Developments and Applications 657 a) Optical b) Fe-map c) Cazr d) Fe-profile f) Optical g) Fe-scan d) e) Fig. 7.129. ( a–g ) Visualization of transport conditions in a column experiment. Image of multiple mushroom-like oxidation fronts in a longitudinal section of the upper 9 cm quartz filling of a pyrite column showing favored transport pathways. The Fe distribution across the mushroom texture mirrors the photograph ( a ) The Ca distribution shows a crust with distinct layers ( c ). The upper crust bends around the edge and incrustrates the outer wall for about 4 cm down the column. The black dots are isolated zircons ( c ) in the sand matrix. A central vertical profile ( d ) shows the intensities of the Fe distribution gaining toward the crust. The cross-section at 9 cm depth ( e ) outlines the dark Fe-rich zone. A horizontal section through the central part of the column ( f ) shows an outer rim in gray, a highly oxidized zone in black and a white core for the photo. The EDXRF Fe map ( g ) shows an enriched zone (white) about 0.5 cm from the rim (see black zone in a). White dots in the center and rim correspond to Fe-rich minerals in the quartz filling. The gray scattered distribution is attributed to Fe-gel coating of quartz grains Plate II 1–5. Continued. 3.1-2. Stratigraphic control: Within salt diapirs a stratigraphic correlation of indi- vidual lamina is often complicated. Detailed EDXRF mapping provides a character- ization of sequences. Folded anhydrite with rock salt cubes with laminated clay and salt injections. The clay sequence shows characteristic Zr-enriched layers. Tectonic injections of clay and rock salt into anhydrite and salt soaked clay layers can be observed. 4.1-4. Optical (4.1) and EDXRF scans of a mineralized breccia from Namibia (Melcher [455]). A composite elemental map (4.2) shows the PbZnCu ore in black, and disseminated and patchy Fe sulfide in red. Mn forms a halo in the dolomite and precipitates as manganiferous–calcite in the ore zone. Earlier calcite veinlets had displaced pulse-like Fe-infiltration zones. The Fe distribution (4.3) shows when clas- sified (4.4) several zones. Dolomite background (blue), infiltration turquoise (yellow highest concentrations), zones of leaching and Cu ore (dark blue), and very low val- ues in Mn-carbonate veinlets and halo zones (purple) are seen. 5.1-2. EDXRF combined elemental distribution map mirroring the mineralogical distribution. For comparison an optical scan outlining plagioclase (Pl), chromitite (Chr), olivine (Ol), and orthopyroxene (OPx) is shown.
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658 D. Rammlmair et al.
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