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Origin of serpentinite-related nephrites from Gogołów-Jordanów Massif, Poland

Gil G., Barnes J. D., Boschi Ch., Gunia P., Szakmány G., Bendő Z., Raczyński P., Péterdi B.

Geological Quarterly

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2015

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Vol. 59, No. 3

457--472

EN

The Gogołów-Jordanów Massif (GJM) in the Fore-Sudetic Block, SW Poland, hosts nephrites traditionally interpreted as serpentinite-related (ortho-nephrite). This contribution confirms the serpentinite-related origin of the nephrites on the basis of mineralogy, bulk-rock chemistry, and O and H isotopes. Rock-forming amphiboles from nephrites of the GJM have 7.73–7.99 Si apfu, comparable to 7.76–8.03 Si apfu of serpentinite-related Crooks Mountain nephrite amphibole (Granite Mountains, Wyoming, USA). The GJM amphiboles also have Mg/(Mg + Fe2+) values ranging from 0.82 to 0.94, similar to serpentinite-related Crooks Mountain and New Zealand nephrites amphiboles with Mg/(Mg + Fe2+) values of 0.86–0.90 and 0.91 to 0.92, respectively. The GJM nephrite amphiboles differ from the Val Malenco dolomite-related nephrite (Italy) amphibole, e.g., Val Malenco has a higher Si content (~8.0 Si apfu), although it overlaps with some of the GJM nephrite samples, and ~1.0 Mg/(Mg + Fe2+), also higher than the GJM samples. Also, apatite in the nephrite studied from the GJM has a slightly higher Ca content than apatite from dolomite-related nephrite. Chlorites found in the Jordanów nephrite have similar compositions to that of chlorites in the serpentinite-related nephrites and also to chlorites associated with serpentinisation/rodingitisation. The bulk-rock FeO vs. Fe/(Fe + Mg), Cr, Ni, and Co are also typical of the serpentinite-related nephrites. The d18O values range from +6.1 to +6.7‰ (±0.1‰), and the average dD values = –61‰, corresponding with the serpentinite-related nephrites range. Based on petrographic observations, we suggest four crystallisation stages (including rodingitisation prior to nephrite formation): 1 – leucogranite rodingitisation and black-wall formation; 2 – tremolite formation at the expense of rodingite diopside and black-wall chlorite (nephritisation) and garnet break-down, with spinel and chlorite formation (chlorite can be a product of garnet break-down or spinel with serpentine reaction); 3 – prehnite vein formation; 4 – tremolite formation at the expense of prehnite veins and actinolite veins formation. Spinels composed of 0.29–1.96 wt.% MgO, 24.87–29.67 wt.% FeO, 8.72–22.82 wt.% Fe2O3, 3.11–4.36 wt.% Al2O3, and 39.07–54.46 wt.% Cr2O3 suggest nephritisation in the greenschist to lower-amphibolite-facies conditions.

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Petrographic and geochemical investigation of a stone adze made of nephrite from the site Balatonőszöd – Temetői dűlő (Hungary)

Péterdi B., Szakmány G., Judik K., Dobosi G., Kasztovszky Z., Szilágyi V., Maróti B., Bendő Z., Gil G.

Geological Quarterly

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2014

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Vol. 58, No. 1

181--192

EN

The present study reports on results of petrographic and geochemical analyses on a stone adze from the archaeological site Balatonőszöd – Temetői dűlő (Hungary). This is the largest excavated site of the Baden Culture in Hungary (more than 200.000 m2) and has the longest continuous settlement history. In the site, features of the Balaton-Lasinja Culture (Middle Copper Age) and the Boleraz Culture were also found. Altogether 500 stone artefacts were found and registered. The present study reports on the results of the investigation of a unique stone adze made of nephrite, found on the site. The nephrite adze found in Balatonőszöd – Temetői dűlő has proved to be the first find made of nephrite having an established archaeological context in Hungarian prehistory. By applying detailed petrographic, geochemical and petrophysical methods as well as comparing data from technical literature we located the origin of the raw material of the nephrite adze. Its most probable source is the Northern part of the Bohemian Massif, Lower Silesia, a geological site near Jordanów (Poland).

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Petrographic and microprobe study of nephrites from Lower Silesia (SW Poland)

Gil G.

Geological Quarterly

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2013

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Vol. 57, No. 3

395--404

EN

Lower Silesia hosts important European nephrite deposits of Jordanów and less-known of Złoty Stok. Nephrite artifacts were discovered in archaeological sites dated back to the Neolithic period, across Eurasia. Especially artifacts found in Poland, Italy and Bulgaria may originate from Polish nephrites. Nowadays, only one artifact is precisely linked to Jordanów. Petrographic study of nephrites and chemical analyses of constituents by means of EMPA allow accurate identification of the nephrites. The characteristic phases of Jordanów tremolite nephrite are rotated and cataclased diopside porphyroblasts with pressure shadows, chlorite layers and nests with interlocking non-pseudomorphic texture and prehnite veins. The presence of hydrogrossular, grossular, titanite, apatite with monazite inclusions, and zircon with pleochroic haloe is typical. Chlorites are usually represented by penninite, and minor clinochlore and diabantite. The characteristic features of Złoty Stok actinolite nephrite are löllingite and diopside crystals usually visible by the naked eye, with the presence of quartz and carbonates. Löllingite is chemically inhomogeneous and gold bearing. Most of the mineralogical-petrological features can be obtained using non-destructive methods.

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Nefryt z Nasławic na Dolnym Śląsku

Łobos K., Sachanbiński M., Pawlik T.

Przegląd Geologiczny

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2008

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Vol. 56, nr 11

991-999

EN

During exploitation of serpentinite in the Nasławice quarry (SW Poland) a nephritic zone has been identified. Nephrite occurs in association with light in color rock, similar to rodingite, composed almost entirely of garnet. These rocks form oval bodies in serpentinites. Their maximal length is 7 m and height is 3.5 m. Nephrite appears in the contact zone of one of such bodies. In the upper contact zone nephrite is 10-15 cm thick and in the west side of the rodingite body reaches 40-50 cm. It is possible to distinguish varieties of nephrite from the Nasławice quarry which differ according to color, fabric and mineral composition. Nephrite from Nasławice is hard and reveals splintery fracture. Nephrite is mainly composed of actinolite, which forms fine- grained aggregates (length of fibres ca 100 um) arranged chaotically. Additional minerals also occur such as chromite, garnet enriched in Cr and pyroxene. Microscopic examination reveals that nephrite has massive, fibrous texture. With regard to gemmological properties, three varieties of nephrite have been identified: 1) Homogenous green nephrite with a small amount of chromite inclusions, which cover no more than 5% of surface of sliced samples; 2) Spotted nephrite-with numerous dark spots on a green background; it happens occasionally, that this variety of nephrite changes into serpentinite; 3) Patchy nephrite- characterized by the presence of emerald-green, elongated spots of actinolite (often with grains of chromite inside) on a white background; some fragments contain veins of fibrous serpentine with cat’s eye effect; this seems to be the most interesting sort of nephrite from Nasławice. Based on preliminary technological studies it can be concluded, that nephrite from Nasławice has not only a fine color and interesting texture, visible in sliced samples, but it is also easy for polishing. On polished surfaces nephrite shows fine oily luster. Unfortunately, examples found today are strongly cracked because of the explosive method of serpentinite exploitation used in the Nasławice quarry. The zone of nephrite occurrence is associated with the course of veins of leucocratic rock which extends over a distance of ca 5 km between Nasławice and Jordanów Sląski.

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Geneza nefrytu z Jordanowa Śląskiego w świetle badań mineralogiczno-geochemicznych

Heflik W., Natkaniec-Nowak L.

Geologia / Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie

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2001

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T. 27, z. 2--4

281-298

PL

W pracy przedstawiono charakterystyką mineralogiczno-geochemiczną nefrytu z Jordanowa Śląskiego koło Sobótki oraz przeprowadzono dyskusję na temat jego genezy. W badaniach zastosowano obserwacje makro- i mikroskopowe, analizę rentgenograficzną, termiczną (DTA), spektrofotometryczną w podczerwieni (IR) oraz chemiczną przy użyciu mikrosondy elektronowej. Z badań wynika, że nefryt z Jordanowa Śląskiego stanowi mieszaninę dwóch faz krystalicznych: tremolitu i aktynolitu. Jest on produktem przeobrażenia skały diopsydowej, która stanowi końcowy dyferencjat gabra diallagowego intrudującego w szczeliny spękań serpentynitu

EN

The study presents mineralogical and geochemical characteristics of the nephrite from Jordanów Śląski near Sobótka and discusses the problem of its genesis. The research consisted of macroscopic and microscopic inspection, X-ray diffraction, differential thermal analysis (DTA), IR spectroscopy, and electron microprobe analysis. The analyses revealed that the nephrite from Jordanów Śląski is a mixture of two mineral phases: tremolite and actinolite. It is a product of metamorphism of a diopside rock which in turn was the final differentiate of a diallague gabbro intruding into fissures within serpentinite rocks