Emerald mineralization during regional metamorphism; the Habachtal (Austria) and Leydsdorp (Transvaal, South Africa) deposits

Grundmann, Günter; Morteani, G.

doi:10.2113/gsecongeo.84.7.1835

Cited by 85 publications

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“…The low beryllium content of stream sediment (1 ppm) and rocks (0.46-21.09 ppm) in the study area is similar to that of other beryl-bearing metamorphic rocks and sediments in nature (Grundmann and Morteani, 1989;Grew, 2002). All major oxide (except SiO 2 and CaO) values decrease in stream sediment, possibly during transportation from altered metamorphic units.…”

Section: Discussionsupporting

confidence: 56%

“…Thus, the concentration of magnesium-rich and beryllium-rich fluid favored the crystallization of beryl (Turner et al, 2005;Grundmann and Morteani, 2008;Groat et al, 2008). The host rock of this type of beryl occurrence is similar to beryl (emerald) deposits that are formed via syn-to post-tectonic reactions under low-grade regional metamorphism and within biotite schist tectonically overlain by ophiolite, such as in southern Egypt (Abdalla and Mohamed, 1999) and Habachtal, Austria, (Grundmann and Morteani, 1989) where the source of chromium is believed to be metasomatized ophiolitic rocks (Groat et al, 2008).…”

Section: Discussionmentioning

confidence: 90%

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Occurrence of Cr-bearing beryl in stream sediment from Eskişehir, NW Turkey

Erkoyun

Kadır

2016

Earth sci. res. j.

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Beryl crystals are found within stream sediments transecting schists in the northeast of Eskişehir, western Anatolia. This paper studied the Eskişehir beryl crystals with optical microscopy, scanning electron microscopy (SEM-EDX), infrared spectroscopy (IR) and geochemical analyses. Beryl is accompanied by garnet, glaucophane, quartz, epidote, muscovite and chlorite in the stream sediments. The crystals are euhedral emerald (green gem beryl) and light bluishgreen aquamarine, with ideal sharp IR bands. Wet chemical analysis of Eskişehir beryl yielded 61.28% SiO2, 15.13% Al2O3, 12.34% BeO, 0.18% Cr2O3, 1.49% MgO, 1.69% Na2O, 0.98% Fe2O3, and 0.008% V2O3, resulting in the formula (Al1.75Cr0.01Mg0.22Fe0.08)(Be2.90Si6.00)(Na0.32)O18. Large Ion Lithophile Elements (LILE) (barium, strontium), some transition metals (cobalt, except nickel) and High Field Strength Elements (HFSE) (niobium, zirconium, and yttrium) in stream sediments that are associated with beryl exhibited low content about metamorphic rocks. Beryl formation appears to be controlled by upthrust faults and fractures that juxtaposed them with Cr-bearing ophiolitic units and a regime of metasomatic reactions. Such beryl crystals have also been found in detrital sediments that are derived from the schists.Cristales de berilio fueron encontrados en sedimentos de corrientes que atraviesan en esquistos en el noreste de Eskisehir, al oeste de Anatolia. En este artículo se presentan resultados sobre el estudio de los cristales de berilio de Eskisehir con microscopio electrónico de barrido (SEM-EDX, del inglés Scanning Electron Microscopy), espectroscopia infrarroja y análisis geoquímicos. El berilio estaba acompañado de granate, glaucofana, cuarzo, epidota, moscovita, y clorito en las corrientes sedmientarias. Los cristales son esmeraldas de formas definidas (gema verde de berilio) y aguamarinas color verde celeste, con bandas de espectroscopia infrarroja de buena nitidez. El análisis químico húmedo del berilio de Eskisehir mostró 61.28 % de SiO2, 15.13 % de Al2O3, 12.34 % de BeO, 0.18 % de Cr2O3, 1.49 % de MgO, 1.69 % de Na2O, 0.98 % de Fe2O3, y 0.008% de V2O3, lo que resulta en la formula (Al1.75Cr0.01Mg0.22Fe0.08)(Be2.90Si6.00)(Na0.32)O18. Los elementos litófilos de ion grande (bario, estroncio), algunos metales de transición (cobalto, excepto níquel) y los elementos de gran campo de fuerza (niobio, circonio e itrio) en las corrientes de sedimentos que están con berilio mostraron un bajo contenido sobre las rocas metamórficas. Las formaciones de berilio aparecen controladas por fallas de cabalgamiento y fracturas que se yuxtaponen con las unidades ofiolíticas relacionadas con cromo y un régimen de reacciones metasomáticas. Estos cristales de berilio se han encontrado también en sedimentos detríticos que se derivan de los esquistos. EARTH SCIENCES

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Section: Discussionsupporting

confidence: 56%

Section: Discussionmentioning

confidence: 90%

Occurrence of Cr-bearing beryl in stream sediment from Eskişehir, NW Turkey

Erkoyun

Kadır

2016

Earth sci. res. j.

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“…Some pegmatite and granodiorite intrusives at Poona were pre-or syn-tectonic, as suggested by their conformable orientation within the regional tectonic fabric and boudinaged textures (cf. [4,8]), and this might indicate that they were related to the Big Bell Suite (2724-2690 Ma), comprising foliated tonalite to monzogranite, which is part of the Austin Downs Supersuite.…”

Section: Geological Settingmentioning

confidence: 99%

Pressure–Temperature–Fluid Constraints for the Poona Emerald Deposits, Western Australia: Fluid Inclusion and Stable Isotope Studies

et al. 2016

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Abstract:Emerald from the deposits at Poona shows micrometre-scale chemical, optical, and cathodoluminescence zonation. This zonation, combined with fluid inclusion and isotope studies, indicates early emerald precipitation from a single-phase saline fluid of approximately 12 weight percent NaCl equivalent, over the temperature range of 335-525 • C and pressures ranging from 70 to 400 MPa. The large range in pressure and temperature likely reflects some post entrapment changes and re-equilibration of oxygen isotopes. Secondary emerald-hosted fluid inclusions indicate subsequent emerald precipitation from higher salinity fluids. Likewise, the δ 18 O-δD of channel fluids extracted from Poona emerald is consistent with multiple origins yielding both igneous and metamorphic signatures. The combined multiple generations of emerald precipitation, different fluid compositions, and the presence of both metamorphic and igneous fluids trapped in emerald, likely indicate a protracted history of emerald precipitation at Poona conforming to both an igneous and a metamorphic origin at various times during regional lower amphibolite to greenschist facies metamorphism over the period~2710-2660 Ma.

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“…The main difference between the two is the Emmaville deposit contains more chromium than vanadium (<0.1 mass% V 2 O 3 ) (Figure 4) and Byrud has minor amounts of CH 4 in the fluid inclusions [30]. Notably, similar emerald banding is also observed from the emeralds in Namibia, specifically from the Erongo Mountains and Leydsdorp in South Africa [31].…”

Section: Discussionmentioning

confidence: 99%

Pressure-temperature-fluid constraints for the Emmaville-Torrington emerald deposit, New South Wales, Australia: Fluid inclusion and stable isotope studies

et al. 2012

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Abstract:The Emmaville-Torrington emeralds were first discovered in 1890 in quartz veins hosted within a Permian metasedimentary sequence, consisting of meta-siltstones, slates and quartzites intruded by pegmatite and aplite veins from the Moule Granite. The emerald deposit genesis is consistent with a typical granite-related emerald vein system. Emeralds from these veins display colour zonation alternating between emerald and clear beryl. Two fluid inclusion types are identified: three-phase (brine+vapour+halite) and two-phase (vapour+liquid) fluid inclusions. Fluid inclusion studies indicate the emeralds were precipitated from saline fluids ranging from approximately 33 mass percent NaCl equivalent. Formational pressures and temperatures of 350 to 400 • C and approximately 150 to 250 bars were derived from fluid inclusion and petrographic studies that also indicate emerald and beryl precipitation respectively from the liquid and vapour portions of a two-phase (boiling) system. The distinct colour zonations observed in the emerald from these deposits is the first recorded emerald locality which shows evidence of colour variation as a function of boiling. The primary three-phase and primary two-phase FITs are consistent with alternating chromium-rich 'striped' colour banding. Alternating emerald zones with colourless beryl are due to chromium and vanadium partitioning in the liquid portion of the boiling system. The chemical variations observed at Emmaville-Torrington are similar to other colour zoned emeralds from other localities worldwide likely precipitated from a boiling system as well.

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Emerald mineralization during regional metamorphism; the Habachtal (Austria) and Leydsdorp (Transvaal, South Africa) deposits

Cited by 85 publications

References 0 publications

Occurrence of Cr-bearing beryl in stream sediment from Eskişehir, NW Turkey

Occurrence of Cr-bearing beryl in stream sediment from Eskişehir, NW Turkey

Pressure–Temperature–Fluid Constraints for the Poona Emerald Deposits, Western Australia: Fluid Inclusion and Stable Isotope Studies

Pressure-temperature-fluid constraints for the Emmaville-Torrington emerald deposit, New South Wales, Australia: Fluid inclusion and stable isotope studies

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