Hydrogeochemical modelling of CO2 equilibria and mass transfer induced by organic–inorganic interactions in siliciclastic petroleum reservoirs

Different feldspar types control complex hydrogeochemical processes in hydrocarbon‐bearing siliciclastic reservoirs, which have undergone different degrees of degradation. To test such processes generically, carbon dioxide equilibria and mass transfers induced by organic–inorganic interactions have been modelled for different hydrogeochemical scenarios. The approach is based on and compared with data from the Norwegian continental shelf ( Smith & Ehrenberg 1989 ) and assumes local thermodynamic equilibrium among solids and fluids. Equilibrating mineral assemblages (different feldspar types, quartz, kaolinite, calcite) are based on the primary reservoir composition. Equilibration and coupled mass transfer were triggered by the addition and reaction of different amounts of CO₂, CH₄ and H₂ (plus acetic acid) at temperatures between 50 and 95°C (323 and 368 K). These components occur in oil fields as products of anaerobic bacterial degradation, hydrolytic disproportionation of hydrocarbons and/or thermal maturation of kerogen. We apply two different computer codes and two different thermodynamic data bases to calculate the results. Reaction of 0.32–0.6 mol CO₂, 0.16–0.3 mol CH₄ and 0.8–1.5 mol H₂ with K‐feldspar, quartz, kaolinite and calcite in 1 l of pore water results in modelled values of 0.3–2.3 mol% CO₂ in a multicomponent gas phase that resembles measured data (0.2–1.5 mol%). Similar CO₂ contents result from acetic acid addition (CO₂, CH₄, H₂ + 0.016 mol CH₃COOH). Equilibration with albite or anorthite reduces the release of CO₂ into the multicomponent gas phase dramatically, by 1 or 4 orders of magnitude compared with the equilibration with K‐feldspar. Minor differences in the modelled CO₂ content (0.1–0.2 mol%) result from calculations with different computer codes if the same thermodynamic data base is applied. Relevant differences (up to 1.9 mol% CO₂) result from calculations using different thermodynamic data bases.     

A PROVENANCE STUDY OF THE GILGAMESH FRAGMENT FROM MEGIDDO

A Late Bronze Age fragment of a clay cuneiform tablet with the Gilgamesh Epic was found in the 1950s on the surface at Megiddo. The presence of scribes in Megiddo is evident from the el‐Amarna letters. This is the only first‐class literary Mesopotamian text ever to be found in Canaan. The aim of the present study was to examine the origin of this tablet, by mineralogical and elemental methods. The petrographic and NAA results indicate that the tablet was not Mesopotamian, but was written in southern Israel. The implications of this result in view of the small corpus of scholarly cuneiform texts discovered in Egypt and the southern Levant in the second millennium bce are discussed.     

Ancient DNA provides new insights into the origin of the Chinese domestic horse

Domestic horses played a pivotal role in ancient China, but their exact origin remains controversial. To investigate the origin of Chinese domestic horses, we analyzed mitochondrial DNA (mtDNA) from 35 horse remains, aged between 4000 and 2000 years, excavated from nine archaeological sites in northern China. The Chinese ancient horses exhibited high matrilineal diversity, falling into all the seven haplogroups (A–G) observed in modern horses. These results suggest that several maternal lines were introduced into the gene pool of Chinese horses in the past. Haplogroups A and F were more prevalent in ancient horses than the other haplogroups. Interestingly, only haplogroups A and F were present in the samples older than 4000 years, while the more recent horses (between 2000 and 3000 years BP) fell into all seven haplogroups. Comparison with DNA data of present-day horses suggests that haplogroup F is like to be an ancient haplogroup of East Asian origin. These analyses also suggest that the origin of Chinese domestic horses is complex, and external mtDNA input occurred after initial domestication. Our results indicate that the Chinese ancient horses are more related to the modern Mongolian horses. Lastly, our results cannot support the previous hypothesis that early Chinese domestic horses were derived from the Przewalski horse.     

‘Novy Svet Ware’, an Exceptional Cargo of Glazed Wares from a 13th‐Century Shipwreck near Sudak (Crimea,Ukraine)—Morphological Typology and Laboratory Investigations

Excavation of a medieval shipwreck at Novy Svet, Crimea, Ukraine, revealed an exceptional quantity of glazed ceramics with sgraffito decoration which, according to chemical analysis, correspond to a single production provisionally named ‘Novy Svet Ware’. Typological and analytical definitions are given. Its diffusion in the Crimea and extending to Turkey and the Levant, points to a main, as yet unlocated, workshop. The Novy Svet shipwreck suggests the persistence of large‐scale diffusion of ceramics in the late‐13th century, and demonstrates connections with the Black Sea, the Byzantine capital and territories, the Mediterranean and possibly the spice roads. © 2009 The Authors     

AN ELEMENTAL AND LEAD‐ISOTOPIC STUDY ON BRONZE HELMETS FROM ROYAL TOMB NO. 1004 IN YIN RUINS

Lead isotope and element composition analyses were performed by thermal ionization mass spectrometry (TIMS) and inductively coupled plasma optical emission spectroscopy (ICP–OES) on bronze helmets from royal tomb No. 1004 at Yin Ruins, the last capital of China's Shang Dynasty (17th to 11th centuries bc ). The data show that the copper‐based alloy helmets can be divided into two categories: tin bronze and leaded tin bronze; and the lead isotope ratios for both categories are in the range of highly radiogenic lead (HRL). This result offers some important clues to answering questions concerning the provenance of raw metal materials, as well as the chronology of this famous royal tomb.     

Paleodietary analysis of the prehistoric population of the Canary Islands inferred from stable isotopes (carbon,nitrogen and hydrogen) in bone collagen

Nitrogen and carbon isotope compositions were measured in the bone collagen from a total of 86 prehispanic samples of the Canary Islands, and hydrogen in 70, all of them with enough amount of bone collagen, and adequate N and C content. These samples belong to prehistoric population of El Hierro (n = 27), Tenerife (n = 18), and Gran Canaria (n = 41). Isotope compositions were also obtained for prehistoric and modern food resources that were likely consumed by these people. Marked differences were observed among the three islands regarding the three isotopes analyzed: the δ¹⁵N values were highest among the population of Gran Canaria (10.8‰ ± 0.9‰), who also showed the highest δD values (7 ± 8‰). The population of El Hierro showed the highest δ¹³C values (−18.6‰ ± 0.7‰). These data suggest a high consumption of marine products by the population from El Hierro, and also an important consumption of terrestrial meat or marine, piscivore fish, by the population from Gran Canaria, together with domesticated C₃ plants (barley and/or wheat), fruits of Ficus carica and other wild species, and goat products. Additionally, marked differences were observed between men and women, which suggest that women consumed a more vegetal-based diet, a finding which is in agreement with the higher proportion of teeth with carious lesions among women.