Decreasing CO2 partial pressure triggered Mg–Fe–Ca carbonate formation in ancient Martian crust preserved in the ALH84001 Meteorite

We retrace hydrogeochemical processes leading to the formation of Mg–Fe–Ca carbonate concretions (first distinct carbonate population, FDCP) in Martian meteorite ALH84001 by generic hydrogeochemical equilibrium and mass transfer modeling. Our simple conceptual models assume isochemical equilibration of orthopyroxenite minerals with pure water at varying water‐to‐rock ratios, temperatures and CO₂ partial pressures. Modeled scenarios include CO₂ partial pressures ranging from 10.1325 to 0.0001 MPa at water‐to‐rock ratios between 4380 and 43.8 mol mol^?1 and different temperatures (278, 303 and 348 K) and enable the precipitation of Mg–Fe–Ca solid solution carbonate. Modeled range and trend of carbonate compositional variation from magnesio‐siderite (core) to magnesite (rim), and the precipitation of amorphous SiO₂ and magnetite coupled to magnesite‐rich carbonate are similar to measured compositional variation. The results of this study suggest that the early Martian subsurface had been exposed to a dynamic gas pressure regime with decreasing CO₂ partial pressure at low temperatures (approximately 1.0133 to 0.0001 MPa at 278 K or 6 to 0.0001 MPa at 303 K). Moderate water‐to‐rock ratios of ca. 438 mol mol^?1 and isochemical weathering of orthopyroxenite are additional key prerequisites for the formation of secondary phase assemblages similar to ALH84001’s ‘FDCP’. Outbursts of water and CO_2(g) from confined ground water in fractured orthopyroxenite rocks below an unstable CO₂ hydrate‐containing cryosphere provide adequate environments on the early Martian surface.     

Main and trace elements in KTB-VB fluid: composition and hints to its origin

The pilot hole (VB) of the German Continental Deep Drilling Program (KTB) was drilled to a depth of 4000 m, where large amounts of free fluids were met. The KTB‐VB 4000 m fluid can be related to either Mesozoic seawater or formation water from Permo‐Carboniferous sedimentary rocks of the Weiden embayment. During the Upper Cretaceous uplift of the Bohemian Massif both fluids could have passed organic‐rich Triassic to Carboniferous formations of the Weiden embayment before invading the uplifted and fractured basement rocks of Devonian amphibolites and metagabbros, where the chemical composition of the fluids was changed by albitization, adularization, and chloritization. Results of chemical mass balances for both sources are presented. In order to concentrate the formation water from the Weiden embayment significant amphibolitization has to be assumed. During a 1‐year pumping test the chemical composition of the 4000 m fluids remained constant. The accuracy of chemical analyses is critically reviewed. An improved preconcentration method of rare earth elements and yttrium in high‐Ca‐bearing saline fluids is described.     

THE OLIVE IN THE PREHISTORIC AEGEAN: THE EVIDENCE FOR DOMESTICATION IN THE EARLY BRONZE AGE

Summary. In 1972 Colin Renfrew suggested that the rise of Mycenaean civilization may have been made possible by the development of a polycultural triad of wheat, vine and olive in the Early Bronze Age. A careful examination of the botanical and archaeological evidence for the domestication of the olive lends little support to this aspect of the thesis. The palynological evidence from various points in Greece is inconclusive, but for most areas it would seem to suggest that the intensive cultivation of olive began in the Late Bronze Age or even later.
No conclusive archaeological evidence for processing or storage of olive oil exists for any period in the Bronze Age. The question of when olive domestication took place must remain unanswered until more data are available from Early and Middle Bronze Age contexts and more conclusive botanical data have been collected.     

A COMPARISON OF INVERSE FILTERING AND MULTIPLE SOURCE WERNER DECONVOLUTION FOR MODEL ARCHAEOLOGICAL PROBLEMS

Inverse filtering and multiple source Werner deconvolution are tested on synthetic data produced by models which simulate features that occur commonly in archaeological exploration. Inverse filtering produces patterns which reflect the magnetization and lateral extent of the subterranean bodies and which are located at their centres. Multiple source Werner deconvolution locates the corners of the bodies with adequate accuracy. Both schemes can provide significant aid in interpreting magnetic data acquired for archaeological exploration.     

The Politics of Citizenship in 1940s Britain: The British Nationality Act

The article examines the enactment of the British NationalityAct, 1948. The legislation created a legal status—Citizenshipof the UK and Colonies—that included Britons and ‘colonial’British subjects under a single definition of British citizenship,and entrenched their right to enter the UK. Between 1948 and1962, some 500, 000 non-white British subjects entered underthe legislation, despite documented evidence of elite suspicionof non-white Commonwealth migration. The article argues thatthis apparent contradiction can only be understood by examiningthe legislation in the context of past migration patterns andBritain's international position in 1948. The legislation wasonly marginally related to migration; it was rather an attemptto maintain a uniform definition of subjecthood in the faceof Canada's unilateral introduction of its own citizenship,and it was an affirmation of Britain's place as head of a Commonwealthstructure founded on the relationship between the UK and theOld Dominions. ^* For comments on earlier drafts, I owe my thanks to John Dorwin,Katie Goebs, Iain McLean, and Desmond King.