Conservation Science and Ethics in the Analytical Studies of Clay Cuneiform Tablets from Ancient Near Eastern Archives

The Late Bronze Age (ca. 1500-1200 BC) constitutes the heyday of the great empires of the ancient Near East (ANE), such as Egypt, Hatti, Mitanni, Babylonia, and Assyria. Centuries of conflicts followed by peaceful relations, marked the interrelations of these superpowers. Rich literary records in the form of archives of cuneiform texts were established. These archives contain abundant tablets whose origin is unknown. Sometimes the letterhead is missing, in other cases, we may have the name of the sender and still ignore his domicile. Further, the location of many ANE countries and cities has not yet been clearly established. Hence, revealing the origin of documents has the potential of shedding new light on the history of the ANE and beyond. The paper will discuss the use of a rich array of nondestructive testing (NDT) and minimally-destructive testing (MDT) methods for studying the composition, technology and provenance of ANE cuneiform tablets. This approach opens new horizons in the interpretation of the clay documents. We applied such analyses on hundreds of tablets from el Amarna, Ras Shamra/Ugarit, Boğazköy/Hattusha, and sites in Cyprus and Israel/Palestine. The research project made during the last decade, serves as the basis for this study. The results raise a set of ethical and practical issues concerning the study and conservation of such precious artifacts

Petrological and geochemical characterisation of the sarsen stones at Stonehenge.

Little is known of the properties of the sarsen stones (or silcretes) that comprise the main architecture of Stonehenge. The only studies of rock struck from the monument date from the 19th century, while 20th century investigations have focussed on excavated debris without demonstrating a link to specific megaliths. Here, we present the first comprehensive analysis of sarsen samples taken directly from a Stonehenge megalith (Stone 58, in the centrally placed trilithon horseshoe). We apply state-of-the-art petrographic, mineralogical and geochemical techniques to two cores drilled from the stone during conservation work in 1958. Petrographic analyses demonstrate that Stone 58 is a highly indurated, grain-supported, structureless and texturally mature groundwater silcrete, comprising fine-to-medium grained quartz sand cemented by optically-continuous syntaxial quartz overgrowths. In addition to detrital quartz, trace quantities of silica-rich rock fragments, Fe-oxides/hydroxides and other minerals are present. Cathodoluminescence analyses show that the quartz cement developed as an initial <10 μm thick zone of non-luminescing quartz followed by ~16 separate quartz cement growth zones. Late-stage Fe-oxides/hydroxides and Ti-oxides line and/or infill some pores. Automated mineralogical analyses indicate that the sarsen preserves 7.2 to 9.2 area % porosity as a moderately-connected intergranular network. Geochemical data show that the sarsen is chemically pure, comprising 99.7 wt. % SiO2. The major and trace element chemistry is highly consistent within the stone, with the only magnitude variations being observed in Fe content. Non-quartz accessory minerals within the silcrete host sediments impart a trace element signature distinct from standard sedimentary and other crustal materials. 143Nd/144Nd isotope analyses suggest that these host sediments were likely derived from eroded Mesozoic rocks, and that these Mesozoic rocks incorporated much older Mesoproterozoic material. The chemistry of Stone 58 has been identified recently as representative of 50 of the 52 remaining sarsens at Stonehenge. These results are therefore representative of the main stone type used to build what is arguably the most important Late Neolithic monument in Europe

Post-collisional tectonomagmatic evolution in the northern Arabian–Nubian Shield: time constraints from ion-probe U–Pb dating of zircon

<p>Ion-probe U–Pb dating of plutonic rocks from the northern Arabian–Nubian Shield in Sinai and southern Israel constrains the timing of late East African batholithic post-collisional calc-alkaline (CA2) magmatism and within-plate alkaline to peralkaline (AL) magmatism to <em>c</em>. 635–590 Ma and <em>c</em>. 608–580 Ma, respectively. The earliest dated CA2 rocks are slightly deformed to undeformed, indicating that penetrative deformation ceased by <em>c</em>. 630 Ma. Within the CA2 suite a change from mafic to felsic magmatism is manifested in most of the region, peaking in a voluminous pulse of granodiorite to granite intrusion at 610–600 Ma. The AL magmatism started contemporaneously with the peak in CA2 felsic activity at <em>c</em>. 608 Ma and lasted until 580 Ma. It includes mostly alkaline and peralkaline granites, probably representing variable degrees of differentiation of similar parental magmas. Thus CA2 and AL granites do not represent different tectonic settings, but coeval derivation from variable sources during crustal extension. The majority of rocks dated in this study show minor to non-existent zircon inheritance and thus indicate very minor interaction with previously formed felsic crust. The rare zircon xenocrysts span a typical East African age range (900–607 Ma) and confirm the absence of older crustal components in the juvenile Arabian–Nubian Shield. </p

Rare earth element evolution and migration in plagiogranites: a record preserved in epidote and allanite of the Troodos ophiolite

Plagiogranites from the Troodos ophiolite in Cyprus are occasionally epidotised, either partially or completely. Epidotisation phenomena include replacement of pre-existing minerals and filling of miarolitic cavities. In addition to epidote, miarolites in one plagiogranite body (located near the village of Spilia) contain coexisting ferriallanite-(Ce) and allanite-(Y). Textural and geochemical evidence indicates that late-stage REE-enriched granitic melt facilitated crystallisation of magmatic ferriallanite- (Ce). High REE contents persisted after fluid exsolution, causing crystallisation of allanite-(Y) from hydrothermal fluids in the miarolites. The REE pattern of the hydrothermal allanite-(Y) is characterised by LREE and Eu depletion, similar to the parent plagiogranitic magma. As allanite had sequestered most of the REE in the fluid, epidote took over as the principle hydrothermal mineral. Epidote in Troodos plagiogranites records a fluid evolutionary trend beginning with REE-rich–Eu-depleted similar to allanite- (Y) and gradually transforming into the REE-depleted– Eu-enriched pattern prevalent throughout ‘conventional’ sub-seafloor fluids. A comparison of allanite-bearing and allanite-absent plagiogranites from the same locality suggests that REE-bearing fluids migrated from the plagiogranites. Similar fluid evolution trends observed in diabase-hosted epidote, located adjacent to a large plagiogranite body, suggest influx of plagiogranite-derived REEbearing fluids. Epidotisation in oceanic settings is usually considered to be the result of alteration by high fluxes of seawater-derived hydrothermal fluids. Although epidotisation by magmatic fluids has been suggested to occur in plagiogranites, our study shows that this autometasomatic process is the dominant mechanism by which epidosites form in plagiogranites. Furthermore, epidotisation of diabase has been attributed solely to seawater-derived fluids, but we show that it is possible for diabase-hosted epidosites to form by migration of plagiogranite-derived fluids.This study was funded by ISF research grant 1044/09 to Yaron Katzir. Niels Jöns and Wolfgang Bach acknowledge support from the DFG-Research Centre/Excellence Cluster ‘The ocean in the Earth system’

Early Carboniferous anorogenic magmatism in the Levant: implications for rifting in northern Gondwana

<p>The Variscan orogenesis in Europe peaked during the Late Devonian–Early Carboniferous times when Gondwanan terranes collided with Laurasia. Hitherto it has been thought that Carboniferous tectonics in northern Arabia and the adjacent parts of NE Africa were broad swells (‘arches’) and depressions (‘basins’) that formed as a far-field contractional effect of the Variscan compression. The discovery of a 351 ± 3 Ma (U–Pb in zircon) within-plate felsic volcanism in the Helez borehole, southern coastal Israel, suggests that the Levant Arch is, instead, extensional in origin. Felsic volcanism was associated with gabbro underplating of the crust, an extreme (~50°C/km) crustal thermal gradient, major uplift, and truncation of the ≥2.5 km section. Taken together with the recent discovery of the ~340 Ma oceanic crust in the Eastern Mediterranean, the Levant Arch is interpreted as an uplifted shoulder of a rift, preceding ocean spreading.</p

The tectono-metamorphic evolution of a dismembered ophiolite (Tinos, Cyclades, Greece)

The six exposures of the Upper tectonic Unit of the Cycladic Massif occurring on the island of Tinos are shown to comprise a metamorphosed dismembered ophiolite complex. The common stratigraphic section consisting of tens-of-metres- thick tectonic slices of mafic phyllites overlain by serpentinites and gabbros is considered to have been derived by a combination of thrusting during obduction and subsequent attenuation by low-angle normal faults. All rock types show evidence of a phase of regional greenschist-facies metamorphism, which in the case of the phyllites is accompanied by penetrative deformation. The greenschist-facies metamorphism in gabbros is preceded by high temperature sea-floor amphibolite-facies alteration, whereas in the serpentinites, the antigorite + forsterite greenschist-facies assemblage overprinted an earlier low temperature lizardite serpentinite. Trace element patterns of the mafic phyllites and a harzburgitic origin of meta-serpentinites suggest a supra subduction zone (SSZ) affinity for the ophiolitic suite. δ81O values of phyllites, gabbros and serpentinites range from 6 to 15‰. Model calculations indicate that such values are consistent with low temperature (50-200 °C) alteration of parent rocks by sea-water at varying water/rock ratios. This would agree with the early low temperature mineralogy of the serpentinites, but the early high temperature alteration of the gabbros would require the presence of 18O-enriched sea-water. The following overall history is suggested for Tinos ophiolitic slices. (1) Oceanic crust was generated at a supra-subduction zone spreading centre with high temperature alteration of gabbros. (2) Tectonic disturbance (its early hot stages recorded in an amphibolitic shear zone at the base of serpentinites) brought the already cooled ultramafics into direct contact with sea-water and caused low-T serpentinization. (3) Tectonism after cooling involved thrusting which caused repetition and inversion of the original order of the oceanic suite. (4) Regional metamorphism of all the ophiolite components at greenschist-facies conditions (∼450 °C) overprinted the early alteration mineralogy. It was probably induced by continued thrusting and piling up of nappes. The Tinos ophiolite, dated as late Cretaceous and genetically related to other low pressure rock-units of the same age in the Aegean, differs in age and degree of dismemberment and metamorphism from ophiolites in mainland Greece

Trace element enrichment in shales and dolostones of the Ardon formation, Ramon, Israel

<p>The shale‒dolostone sequence of the Jurassic Ardon formation marks the first marine transgression and deposition after ~15 m.y. long hiatus represented by the Mish'hor formation laterites.</p> <p>Shales and dolostones of the Ardon formation are enriched in trace elements compared to a global average shale composition (PAAS). The trace element signature of dolostones is dominated by the detrital component, because trace element contents of carbonates are negligible. Both rock types are LREE (La‒Nd) enriched by a factor of 1.5. Shales are also HREE (Tb‒Lu) enriched by a factor of 2‒2.5 whereas Zr and Hf show an enrichment by a factor of 2.5‒3 and are linearly correlated. In dolostones, however, MREE (Sm‒Gd) are enriched by a factor of 2.5‒2.7 and Y is also slightly enriched (Y/Ho≈1.1).</p> <p>The cause for the enrichment is currently unknown. Shales from the Ardon formation are usually considered to be recycling of the underlying Mish'hor formation. On the one hand, enrichment and correlation of Zr and Hf suggest that zircon is concentrated in the shales. However, the amount is not sufficient to account for the elevated HREE contents and other heavy minerals could be responsible. On the other hand, laterites are commonly enriched in REE worldwide so it is possible that the shales represent an average value of enrichment that occurred in the precursor Mish'hor formation. The enrichment pattern of the detrital component of the dolostones is different, suggesting a different source for the detrital material. The MREE and Y enrichments are enigmatic.</p> <p>Sr isotope analysis of the carbonate fraction of one dolostone sample gives a 87Sr/86Sr ratio of 0.707442±0.000016. Assuming that the ratio has not changed since primary deposition, we are able to corroborate the age of the Ardon formation to Sinemurian, at ~195 Ma. This would also indicate that the dolomites of the Ardon formation formed penecontemporaneously to the deposition of the unit.</p> <p>The shale‒dolostone sequence of the Ardon formation provides a promising direction for research on both provenance studies and trace element enrichment in sedimentary rocks.</p