Search

This paper examines the history of glass colouring. It reviews Kit?b al-Durra al-makn?naof J?bir ibn ?ayy?n, which deals with the subject. The manuscript of this practical treatise was discovered recently. Part one of the paper deals with J?bir as a philosopher and chemist. The art of lustre-painting on glass originated in Syria during the Umayyad Caliphate in the eighth century and was soon practised in the neighbouring area. The paper reviews Arabic literature that deals with the colouring of glass until the 13th century, and with pre-Islamic and Latin books of recipes that deal with glass colouring. Recipes for cast coloured glass are very few and scant in non-Arabic literature, and lustre-painting on glass was not mentioned in any treatise outside Arabic, even in the works of Theophilus and Neri. The colouring of glass gemstones by colour diffusion is not mentioned also. The paper compares the recipes of Kit?b al-Durrawith the results of modern analysis of existing Islamic stained glass objects. There is a close correspondence, and the main indispensable ingredients in both cases are silver and copper compounds. Part one ends with an account of l?zawardas cobalt oxide in glass colouring. Part two of the paper gives a representative selection of recipes from Kit?b al-Durrafor the three methods of glass colouring. [ABSTRACT FROM AUTHOR]

Copyright of Ancient Mesoamerica is the property of Cambridge University Press and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Middle Neoproterozoic igneous rocks are widespread in South China, but their petrogenesis and tectonic implications are still highly controversial. The Guangfeng middle Neoproterozoic volcani-sedimentary succession was developed on a rare Sibaoan metamorphic basement (the Tianli Schists) in the southeastern Yangtze Block, South China. This paper reports geochronological, geochemical and Nd isotopic data for the volcanic rocks in this succession. The volcanic rocks consist of alkaline basalts, andesites and peraluminous rhyolites. SHRIMP U-Pb zircon age determinations indicate that they were erupted at 827 ± 14 Ma, coeval with a widespread episode of anorogenic magmatism in South China. Despite showing Nb-Ta depletion relative to La and Th, the alkaline basalts are characterized by highly positive ϵNd(T) values (+3.1 to +6.0), relatively high TiO2 and Nb contents and high Zr/Y and super-chondritic Nb/Ta ratios, suggesting their derivation from a slab melt-metasomatized subcontinental lithospheric mantle source in an intracontinental rifling setting. The andesites have significantly negative ϵNd(T) values (-9.3 to -11.1) and a wide range of SiO2 contents (57.6-65.6 %). They were likely generated by the mixing of fractionated basaltic melts with felsic melts derived from the Archaean metasedimentary rocks in the middle to lower crust. The rhyolites are highly siliceous and peraluminous. They are characterized by depletion in Nb, Ta, Sr, P and Ti and relatively high ϵNd(T) values (-3.0 to -4.8), broadly similar to those of the adjacent c. 820 Ma peraluminous granitoids derived from the Mesoproterozoic to earliest Neoproterozoic sedimentary source at relatively shallow levels. We conclude that the Guangfeng volcanic suite is a magmatic response of variant levels of continental lithosphere (including lithospheric mantle and the lower-middle to upper crust) to the middle Neoproterozoic intracontinental rifling possibly caused by mantle plume activity. [ABSTRACT FROM AUTHOR]

The Friedenstein Palace in Gotha, Germany, holds a Late Postclassic Mesoamerican bird head sculpture made of wood encrusted with precious stone and shell mosaic. Although known since the nineteenth century, scholars have not given the artifact the attention it deserves. Based on observations made during a thorough in situ inspection, we provide a detailed description of the object, stressing both technological and aesthetic aspects, documented through new photos and reconstructive drawings prepared by Nicolas Latsanopoulos. Then, we offer an interpretation of the artifact's iconography, demonstrating it should be understood as a representation of the Wind God in its manifestation as a Tzitzimitl, a category of deities associated with creation and destruction; an aspect made evident in the small figure adorning the avian forehead. We finally reconstruct the collection history of the object, suggesting that the Giustiniani family, a prominent Roman noble family renowned for its collecting activities, once owned the sculpture; in turn, this proposal might imply that the Dominican friar Domingo de Betanzos brought the mosaic to Italy in 1532 and that it might be originally from the Puebla-Tlaxcala Valley or, more broadly, from the south-central area of the modern state of Puebla. [ABSTRACT FROM AUTHOR]

The Neoproterozoic Hedmark Basin in the Caledonides of South Norway was formed at the western margin of the continent Baltica by rifting 750–600 Ma ago. The margin was destroyed in the Caledonian Orogeny and sedimentary basins translated eastwards. This study uses provenance analysis to map the crustal architecture of the pre-Caledonian SW Baltican margin. Conglomerate clasts and sandstones were sampled from submarine fan, alluvial fan and terrestrial glacigenic sedimentary rocks. Samples were analysed for U–Pb isotopes and clast samples additionally for Lu–Hf isotopes. The clasts are mainly granites c. 960 Ma and 1680 Ma old, coeval with the Sveconorwegian Orogeny and formation of the Palaeoproterozoic Transscandinavian Igneous Belt (TIB). Mesoproterozoic (Sveconorwegian) ages are abundant in the western part of the basin, whereas Palaeoproterozoic ages are common in the east. Lu–Hf isotopes support crustally contaminated source for all clasts linking them to Fennoscandia. Detrital zircon ages of the sandstones can be matched with those from the granitic clasts except for ages within the range 1200–1500 Ma. These ages are typically found in the present-day Telemark, SW Norway. The sandstones and conglomerate clasts in the western part of the Hedmark Basin were sourced from the Sveconorwegian domain in the present SW Norway or its continuation to the present-day NW. The conglomerate clasts in the eastern part of the Hedmark Basin were sourced mainly from the TIB domain or its northwesterly continuation. The Hedmark Basin was initiated within the boundary of two domains in the basement: the TIB and the Sveconorwegian domains. [ABSTRACT FROM AUTHOR]

Of the increasing number of Roman gemstones from Turkey published from museum and private collections, nearly all lack a secure archaeological context. Consequentially, it has been difficult to discuss the origin, production or dissemi¬nation of gemstones in Anatolia during the imperial period. Excavations in the cemeteries at Gordion have yielded over a dozen carved intaglios typical of the first to the fourth century AD. Three of the gems are cut in a relatively rare octagonal form, an eight-sided shape which achieved limited popularity during the late imperial period but has yet to receive scholarly treatment. The recent recovery of similar late Roman octagonals from other central Anatolian sites has indicated strongly that this particular gemstone type was popular and possibly produced locally in central Turkey. Examination of octagonals as a distinct group, via analyses of gem type, dimension, provenance, date and iconographic representation as evident in a newly-constructed corpus of 185 examples, appears to provide additional support for this theory. It is suggested here that the octagonal shape held numeric and symbolic significance among the military and early Christian communities of central Turkey, where a permanent workshop catering to that mixed clientele possibly existed in at least one of the principal urban centres, at Ancyra and/or Caesarea. [ABSTRACT FROM PUBLISHER]

Age spectra of detrital zircons from metamorphosed quartzites of the Krkonoše–Jizera Massif in the northeastern part of the Saxothuringian Domain were obtained by U–Pb laser ablation inductively coupled plasma mass spectrometry dating. The zircon ages cluster in the intervals of 450–530 Ma and 550–670 Ma, and show individual data between 1.6 and 3.1 Ga. Zircons in the analysed samples are predominantly of Cambrian–Ordovician and Neoproterozoic age, and the marked peak at c. 525–500 Ma suggests a late Cambrian maximum age for the sedimentary protolith. Detritus of the quartzites probably originated from the erosion of Cambrian–Ordovician granitoids and their Neoproterozoic (meta)sedimentary or magmatic country rocks. The lack of Neoproterozoic (meta)sedimentary rocks in the central and eastern part of the Krkonoše–Jizera Massif suggests that the country rocks to voluminous Cambrian–Ordovician magmatic bodies were largely eroded during the formation of early Palaeozoic rift basins along the southeast passive margin of the Saxothuringian Domain. The detrital zircon age spectra confirm the previous interpretation that the exposed basement, dominated by Neoproterozoic to Cambrian–Ordovician granitoids, was overthrust during Devonian–Carboniferous subduction–collision processes by nappes composed of metamorphosed equivalents of the uppermost Cambrian–Devonian passive margin sedimentary formations. Only a negligible number of Mesoproterozoic ages, typically from the Grenvillian event, supports the interpretation that the Saxothuringian Neoproterozoic basement has an affinity to the West African Craton of the northwestern margin of Gondwana. [ABSTRACT FROM PUBLISHER]

The “resource curse” can strike countries that derive a large portion of their national income from exporting high-value natural resources, such as oil, gas, metals, and gems. Resource-exporting countries are subject to four overlapping curses: they are more prone to authoritarianism, they tend to suffer more corruption, they are at a higher risk for civil wars, and they exhibit greater economic instability. [ABSTRACT FROM PUBLISHER]

Seven granitoid gneisses from the contact zone between the eastern margin of the Variscan belt and the Brunian microcontinent in SW Poland have been dated by ion-microprobe and 207Pb/206Pb single zircon evaporation methods. The zircons define two age groups for the gneiss protoliths: (1) late Neoproterozoic c. 576-560 Ma and (2) early Palaeozoic c. 488-503 Ma granites. The granitoid gneisses belonging to the basement of the Brunian microcontinent contain abundant Mesoproterozoic to latest Palaeoproterozoic inherited material in the range of 1200-1750 Ma. The gneisses of the Variscan crustal domain lack Mesoproterozoic inherited zircon cores. Trace element geochemistry of Proterozoic gneisses reveals features resembling either volcanic arc or post-collisional granites. The studied rocks are geochemically similar to other Proterozoic orthogneisses derived from the basement of the Brunian microcontinent. Gneisses with early Palaeozoic protolith ages are geochemically comparable to granitoid gneisses widespread in the adjacent Sudetic part of the Bohemian Massif and are considered characteristic of peri-Gondwanan crust. Our data prove the dissimilarity between the Brunia plate and the westerly terranes of the Variscan belt. The occurrence of granitic gneisses with late Neoproterozoic protolith ages and widespread Mesoproterozoic inheritance in our dated samples support an East Avalonian affinity for the Brunian microcontinent. In contrast, the abundance of gneisses derived from an early Palaeozoic granitic protolith and devoid of Mesoproterozoic zircon cores supports the Armorican affinity of the Variscan domain bordering on the Brunia plate from the west. Structural evidence shows that the eastern segment of the Variscan belt is juxtaposed against the Brunian microcontinent along a N-S-trending tectonic contact, possibly equivalent to the Rheic suture. [ABSTRACT FROM AUTHOR]

Composite Sensitive High Resolution Ion Microprobe (SHRIMP) U-Pb zircon and 40Ar-39Ar step-heating biotite-hornblende ages are used to provide constraints on the timing and origin of the felsic gneissic rocks in the Baiyunshan Mountains region and to elucidate their tectonothermal history. SHRIMP dating and CL imaging of zircons give magmatic zircon crystallization ages between Late Ordovician and Early Silurian (c. 453.5 Ma, 446 Ma, and 439 Ma) for three representative felsic gneisses, suggesting that most of the Baiyunshan gneiss cannot represent basement rocks of the Cathaysia Block as previously thought. Including the present age information, a synthesis of available age data for regional Wuyun (Wuyi-Yunkai) events reflects the emergence of orogen-wide magmatism that could be syn-orogenic and have occurred mainly between 460 and 420 Ma in the South China Block. Inherited zircons are abundant, with ages clustering at late Mesoproterozoic (1189-1017 Ma) and middle Mesoproterozoic (772 Ma), which reveals that the Baiyunshan orthogneiss samples a crustal basement containing significant igneous or recycled components related to the Rodinia amalgamation and break-up. A SHRIMP date of 212 ± 12 Ma from a white rim of zircon provides evidence for metamorphic overprinting of an Indosinian tectonothermal event on the Baiyunshan gneiss. Incremental heating experiments with six biotite samples and one hornblende sample from a variety of metamorphic rocks yielded two distinct 40Ar-39Ar age groups: 150-155 and 94-98 Ma. The older ages are similar to zircon U-Pb dates for widespread granitic intrusions in central Guangdong. We attribute them to Late Jurassic magmatism-induced thermal resetting of the biotite K-Ar system. On the other hand, the younger age group is interpreted to record either cooling through the biotite closure temperature of ~300-350 °C or a second resetting of biotite Ar isotopes at c. 94-98 Ma due to contemporaneous magmatic activity. Our present age data suggest that the Maofengshan orthogneiss was exhumed to 8 to 10 km crustal levels at c. 150 Ma, whereas the eastward components of gneissic rock masses appear to have passed upward through the same crustal depth synchronously or later (by c. 94 Ma). Exhumation of middle crustal-level rocks in the study area since c. 155 Ma is roughly coeval with exhumation of gneissic rocks from elsewhere in the Wuyun Orogen, suggesting a large-scale mechanism for the exhumation pulse related to the Yanshanian extensional tectonic regime. [ABSTRACT FROM AUTHOR]

A new high precision U-Pb zircon age of 710.8 ± 1.5 Ma for granophyric granitic rock from the Stanner Hanter Complex of the Welsh Borderland lies just within error of an older Rb-Sr isochron age. eNd values of -0.3 and -1.2 combined with TDM of 1394 Ma and 1468 Ma indicate that the magma incorporated an older crustal source component. The Nd data highlight differences with western Avalonia, the widely considered Late Neoproterozoic north American counterpart to southern Britain, and point toward a closer similarity with other Peri-Gondwanan terranes that incorporate older, cratonic source material. [ABSTRACT FROM AUTHOR]

The large Variscan Karkonosze Granite in the West Sudetes, representative of the vast Variscan granite plutonism in Central Europe and located adjacent to regional tectonic suture and strike-slip-zones, has been difficult to date precisely; a range of published data varies between c. 304 and 328 Ma. However, the granite is cut by locally numerous lamprophyre and other dykes. Dating of the dyke rocks, emplaced shortly after the granite intrusion and cooled more rapidly, provides a promising tool for the verification of published SHRIMP results on the granite itself. SHRIMP zircon geochronology of a studied micromonzodiorite dyke indicates substantial admixture of inherited zircons of c. 2.0, 1.4 Ga (207Pb-206Pb minimum ages), and c. 570 (and 500?) Ma. The average concordia age of the main magmatic population of the zircons in the dyke is 313 ±3 Ma (2s); however, the true magmatic age might be older, around 318 Ma. This would constrain the age of the hypabyssal magmatism in the Karkonosze Massif and the minimum age of the host Karkonosze Granite. Thus, the Karkonosze Granite is confirmed as representative of an early phase of Variscan granite plutonic activity in the central-European Variscides. [ABSTRACT FROM AUTHOR]

New whole rock Rb-Sr and zircon U-Pb geochronological data and Sm-Nd isotopic data are presented from the central magmatic arc domain of the Antarctic Peninsula in the area of north-west Palmer Land and south-west Graham Land, Rb-Sr isochrons indicate an age of 169 ± 6 Ma for basement orthogneisses and 132 ± 9 to 71 ± 9Ma for plutons. A U-Pb age of 183 ± 2.1 Ma, with no detectable inheritance, on zircons from an orthogneiss from Cape Berteaux provides the first reliable age for the orthogneisses, which are interpreted as metamorphosed silicic volcanic rocks, and Sm-Nd data indicate derivation in a mature volcanic arc. The age indicates they may be correlatives of the Jurassic 'Chon Aike' volcanism of the eastern Antarctic Peninsula. A U-Pb zircon age of 107 ± 1.7 Ma on a terrestrial volcanic sequence overlying an uncomformity strongly suggests a mid-Cretaceous age for the extensive volcanic cover of north-west Palmer Land that was previously thought to be Jurassic. The unconformity is interpreted to have been a result of compressional uplift related to the Palmer Land event. This is the first date for the event in the western part of the central magmatic arc terrane of the Antarctic Peninsula. [ABSTRACT FROM AUTHOR]

Zircon and apatite fission track (AFT) thermochronology was applied to the James Ross Basin sedimentary rocks from James Ross and Seymour islands. The probable sources of these sediments were generated in Carboniferous to Early Paleogene times (∼315 to 60 Ma). The total depths of individual James Ross Basin formations are discussed. The AFT data were modelled, and the thermal history model was reconstructed for samples from Seymour Island. The first stage after a period of total thermal annealing (when the samples were above 120°C) involved Late Triassic cooling (∼230 to 200 Ma) and is followed by a period of steady cooling through the whole apatite partial annealing zone (PAZ, 60-120°C) to minimum temperature in Paleocene/Early Eocene. The next stage was the maximum burial of sedimentary rocks in the Eocene (∼35 Ma, 1.1-1.8 km) and the final cooling and uplift of Seymour Island sedimentary rocks at ∼35 to 20 Ma. [ABSTRACT FROM AUTHOR]

Thin-section observations and electron probe analyses, and trace element data are reported from a new mantle xenolith hosted in Miocene alkali basalt from the western flank of Simien shield volcano, Ethiopia. The spinel lherzolite enclaves contain variable proportions of olivine, orthopyroxene, green clinopyroxene and brown spinel, and have undergone deformation and partial recrystallization. They represent unmetasomatized, fertile xenoliths which were subjected to a late-stage melt-rock reaction. Trace element contents of clinopyroxene crystals are extremely low and quite different from those of the other xenoliths within the East African Rift System. [ABSTRACT FROM AUTHOR]

We report on the newly discovered almandine garnet phenocrysts in rhyolitic ignimbrites (Sukhda Tuff) in the Precambrian Churtela Shale Formation of the Chhattisgarh Supergroup in central India. SHRIMP ages of igneous zircon from the ignimbrites range from 990 Ma to 1020 Ma. These ignimbrites exhibit characteristic eutaxitic texture with compacted curvilinear glass shards with triple junctions. Quartz (commonly embayed; bluish cathodoluminescence) and albite (altered but retaining ghosts of twinning) are common phenocrysts; others are apatite, ilmenite, rutile, magnetite, zircon, monazite and garnet. There are no metamorphic or granitic xenoliths in the ignimbrites. Garnet grains occur as isolated broken isotropic crystals with sharp or corroded boundaries in a very fine-grained groundmass of volcanic ash that consists principally of albite, quartz, magnetite and glass. They do not have any systematically distributed inclusions. A few have penetratively intergrown phenocrysts of apatite, ilmenite, rutile and zircon, which we interpret as subophitic texture. Extensive SEM-BSE imaging of more than 100 grains and electron microprobe traverses across about 30 grains showed no zoning or systematic compositional variability. Common (metamorphic) garnets are usually zoned with respect to Fe-Mg-Mn and typically have mineral inclusions. We infer, therefore, that these observed garnets are not metamorphic xenocrysts. The average major oxide composition of analysed garnets from five different horizons within the Sukhda Tuff, spanning approximately 300 m of the stratigraphic section, have very small standard deviation for each element, which is suggestive of a single magmatic source. Phenocrysts of quartz, including those in contact with coexisting garnets, show blue scanning electron CL, indicating rapid cooling from high temperature; this suggests that adjacent coexisting garnets are not slowly cooled restites. We conclude, on the basis of texture, mineral chemistry and absence of any indicative xenoliths or xenocrysts, that these almandine garnets (Al 78.7 Py 12.3 Gr 7.4 Sp 1.6 ) are phenocrysts within the Sukhda Tuff. Almandine of such composition is stable under high pressure. We infer that almandine crystallized at lower crustal depths in a magma that ascended very rapidly and may have erupted explosively. [ABSTRACT FROM AUTHOR]

The article discusses Africa's participation in the global economy by examining the illegal mining trade in Madagascar. It describes the role of transnational criminalized networks in the gem trade and how this industry produces exclusion, marginalization, integration and wealth. The author declares that the relationship between the illegal gem trading in Madagascar and global gem production and exchange creates a connection as well as a disconnection between Africa and the global economy.

We report here a garnet-spinel orthopyroxenite in close association with an ultrahigh-temperature (UHT) granulite from the central part of the Madurai Granulite Block in southern India. The garnet spinel orthopyroxenite is almost entirely composed of orthopyroxene, spinel and rare garnet in a granular texture. Spinels in the rock are characterized by high Mg (XMg = 0.69-0.71) with low Cr and Fe3+, consistent with compositions reported from spinels occurring within xenoliths in kimberlites and high pressure temperature (P-T) Alpine complexes. The orthopyroxenes have high Al content (Al2O3 up to 4.85 wt %), typical of equilibration under high P-T conditions. The P-T estimates derived for the garnet-spinel orthopyroxenite indicate temperatures of around 1000 °C and pressures exceeding 17 kbar. The data indicate that UHT metamorphism in this locality traversed from above 17 kbar to 11 kbar prior to the final stage of isothermal decompression. Our study reports the highest pressures obtained by far, for extreme crustal metamorphism in southern India and elsewhere in Gondwana. The multi-stage decompression observed in the UHT rocks associated with the high P-T garnet-spinel orthopyroxenite could be correlated to extension of the crust and possibly of the lithospheric mantle and/or its delamination, with the asthenospheric mantle as the ultimate heat source, during the final stage of amalgamation of the Gondwana supercontinent. [ABSTRACT FROM AUTHOR]

The North-East Greenland eclogite province is divided into a western, central and eastern block by the sinistral Storstrømmen shear zone in the west and the dextral Germania Land deformation zone in the east. A family of steep, NNW-striking dextral mylonite zones in the Danmarkshavn area are geometrically and kinematically similar to the ductile Germania Land deformation zone, located 25 km to the east. Amphibolite facies deformation at Danmarkshavn is characterized by boudinage of facies deformation at Danmarkshavn is characterized by boudinage of facies deformation at Danmarkshavn is characterized by boudinage of eclogite bodies within quartzofeldspathic host gneisses, pegmatite emplacement into the boudin necks and subsequent deformation of pegmatites parallel to gneissosity, a widespread component of dextral shear within the gneisses, and localization of strain into 10-50 m thick dextral mylonite zones. The gneisses and concordant mylonite zones are cut by a swarm of weakly to undeformed, steeply dipping, E-W-striking pegmatitic dykes. Oscillatory-zoned zircon cores from two boudin neck pegmatites give weighted mean 206Pb/238U sensitive, high mass resolution ion microprobe (SHRIMP) ages of 376±5 Ma and 343±7 Ma. Cathodoluminescence images of these zircons reveal complex additional rims, with ages from ranging from c. 360 to 320 Ma. Oscillatory zoned, prismatic zircons from two late, cross-cutting pegmatites yield weighted mean 206Pb/238U SHRIMP ages of 343±5 Ma and 332±3 Ma. Zircons from the boudin neck pegmatites record a prolonged growth history, marked by fluid influx, during amphibolite facies metamorphism beginning at c. 375 Ma. The cross-cutting pegmatites show that dextral deformation in the gneisses and ductile mylonite zones had stopped by c. 340 Ma. Ultrahigh-pressure metamorphism in the eastern block at 360 Ma requires that the Greenland Caledonides were in an overall contractional plate tectonic regime. This, combined with 20 steep amphibolite facies lineations in the eclogites, gneisses and mylonites suggests that dextral transpression may have been responsible for a first stage of eclogite exhumation between 370 and 340 Ma. [ABSTRACT FROM AUTHOR]