Rates of retrograde metamorphism and their implications for crustal rheology

The rate of reaction of a natural hornblende garnet granulite with water under a range of mid- to lower crustal conditions has been investigated experimentally. In runs of between 7 and 84 days small but measurable amounts of water were consumed, and sheet silicates (300°C, 300 MPa and 400°C, 400 MPa) and/or secondary actinolite (400°C, 400 MPa and 500°C, 500 MPa) were observed to have grown. When normalized to the surface area of the starting materials, hydration rates were in the range of 2–5 × 10⁻⁸ g m⁻² sec⁻¹. These reaction rates imply that a film of water that infiltrated a planar crack with a half width of 100 μm would be completely consumed within c. 100 years. These results imply that where water infiltrates the crust along faults or underlying shear zones in response to a deformation, it will remain as a free phase for only a finite period of time, which in some cases will be less than the repeat time for major earthquakes in the fault system. Thus, the rheology of fault zones and shear zones is likely to be cyclical, with the zone becoming stronger with time as water is consumed, and then weakened by infiltration of water after each rupture.     

Simulation of adsorption of gold nanoparticles carried by gas ascending from the Earth’s interior in alluvial cover of the middle–lower reaches of the Yangtze River

The adsorption onto other minerals of charged gold nanoparticles, carried by gas ascending from the Earth’s interior, is an important component of their transport and deposition in surficial cover such as alluvial, aeolian, and glacial sediments. To simulate the adsorption of these particles, an experiment was conducted in which a flow of air that contained gold nanoparticles was passed upward through a sample of alluvium from the middle–lower reaches of the Yangtze River. These experiments showed that gold nanoparticles are adsorbed on kaolinite, halloysite, goethite, and hematite in the alluvial cover. Both the gold nanoparticles and minerals (i.e., kaolinite, halloysite, goethite, and hematite) carry surface charges that provide them with excellent adsorption properties. This study showed that the specific mineral composition of surficial alluvial cover affects the concentration of gold nanoparticles in the ascending gas. This phenomenon may plausibly be used in exploration for concealed gold, copper–gold, and silver–gold deposits in areas of thick alluvial cover. Geofluids (2010) 10 , 438–446     

A NEW METHOD FOR EXTRACTION,ISOLATION AND TRANSESTERIFICATION OF FREE FATTY ACIDS FROM ARCHAEOLOGICAL POTTERY

This paper presents evidence for increased recovery of organic residues from archaeological pottery through use of a microwave‐assisted liquid chromatography protocol. C_16:0 and C_18:0 saturated fatty acids were obtained from archaeological potsherds recovered from nine Neolithic settlements in the Middle East dating between 4700 and 7300 cal bc , including materials that had not produced evidence for the survival of any lipid species through use of ‘conventional’ solvent extraction techniques. Compound‐specific isotopic analyses of C_16:0 and C_18:0 fatty acids in potsherd extracts subsequently revealed δ¹³C/δ¹²C compositions consistent with modern subcutaneous fats of wild boar and goats pastured on lands adjacent to the Jordan Valley, and residues from a modern pottery vessel used in the manufacturing of butter, cheese and yogurt in central Turkey. These results are presented as an illustration of capabilities of the microwave‐assisted recovery protocol. The reclamation of saturated and unsaturated fatty acids from archaeological pottery fragments recovered from a number of the earliest ceramic horizons in the Middle East is herewith reported, and the extraction methods and instrumental analytical techniques are described.     

THE DISCOVERY OF AN ANGLO‐SAXON GRUBENHAUS AT NEW BEWICK,NORTHERN UK USING ELECTRICAL SURVEYING AND PREDICTIVE DECONVOLUTION

Twin‐probe and 33‐fold multiplexed Wenner electrical resistivity surveys were carried out at New Bewick, northern UK to examine the extent of crop marks and potential Grubenhäuser (sunken‐featured buildings, sunken‐floored buildings or SFBs). The twin‐probe method was faster, but provided data with a lower spatial resolution. However, the Wenner array data was affected by characteristic ‘M’‐ or ‘W’‐shaped responses over filled excavations such as those expected to represent a Grubenhaus. The raw Wenner array data have been analysed using one‐dimensional and two‐dimensional predictive deconvolution in order to remove these artefacts. The deconvolution was carried out using an inverse matrix element method. The filtered results indicate the presence of anomalies consistent with the presence of at least six Grubenhäuser and other anomalies concurrent with the linear crop‐marks. One particular anomaly measured about 5 m by 4 m and with a pit depth of 0.6 m below 0.3 m of topsoil. This anomaly was subsequently excavated and a Grubenhaus was discovered at the site. The excavated Grubenhaus measured 4.7 m by 3.9 m with a pit depth of 0.5 m below the base of the topsoil, confirming the electrical survey results.     

THE USE OF OXYGEN ISOTOPES IN SHEEP MOLARS TO INVESTIGATE PAST HERDING PRACTICES AT THE NEOLITHIC SETTLEMENT OF ÇATALHÖYÜK,CENTRAL ANATOLIA

This paper presents a pilot study designed to test the use of oxygen isotopes for investigating aspects of early herding practices in the Neolithic of western Asia, using the site of Çatalhöyük in central Anatolia as a case study. Time‐sequenced δ¹⁸O values in dental enamel of archaeological sheep are assessed for post‐depositional diagenetic effects and compared with seasonal δ¹⁸O meteoric water values in the region today. The evidence is used to indicate the environmental conditions in which individual sheep spent their first year, enabling management of breeding and birthing seasons, and movement to seasonal pastures, to be investigated.     

Provenance study of early and middle bronze age pottery from Kaman-Kalehöyük,Turkey, by heavy mineral analysis and geochemical analysis of individual hornblende grains

The provenance of Early Bronze Age and early Middle Bronze Age pottery produced between 2100 and 1970 B.C. and excavated from Kaman-Kalehöyük, Turkey was studied using mineralogical methods, including heavy mineral analysis and geochemical study of individual hornblende grains. The relative abundances of heavy minerals in the fabrics of 20 Early Bronze Age (EBA) and early Middle Bronze Age (MBA) pottery sherds, together with 27 local sediments collected within a radius of 25 km of the site were studied. The heavy mineral distributions in the Kaman region were statistically analyzed for consistencies in their occurrence. Amphibole was found to be the most abundant heavy mineral in most of the analyzed samples, followed by titanite and epidote. The amounts of other minerals such as garnet, clinopyroxene, and zircon are subordinate. Different proportions of heavy minerals in the fabrics allow categorization of the EBA and early MBA potteries into 5 groups. Comparative study of heavy mineral assemblages of local sediments and pottery suggests that half of the EBA and most of the MBA potteries were produced from sediment near the excavation site, whereas the other half of the EBA potteries were produced from sediment occurring at 25 km east or more east of the site. The geochemistry of individual amphibole grains was studied by electron-microprobe analysis. Most of the studied amphibole grains are calcic and aluminous, corresponding to hornblende. They can be further characterized into four types based on their chemical composition. The combination of heavy mineral identity and hornblende geochemistry provides diagnostic evidence for the origins of Kaman-Kalehöyük pottery. These and analogous heavy mineral techniques are effective archaeometric tools for determining pottery provenance.