A vector of high‐temperature paleo‐fluid flow deduced from mass transfer across permeability barriers (quartz veins)

Quartz veins acted as impermeable barriers to regional fluid flow and not as fluid‐flow conduits in Mesoproterozoic rocks of the Mt Painter Block, South Australia. Systematically distributed asymmetric alteration selvedges consisting of a muscovite‐rich zone paired with a biotite‐rich zone are centered on quartz veins in quartz–muscovite–biotite schist. Geometric analysis of the orientation and facing of 126 veins at Nooldoonooldoona Waterhole reveals a single direction along which a maximum of all veins have a muscovite‐rich side, irrespective of their specific individual orientation. This direction represents a Mesoproterozoic fluid‐flow vector and the veins represent permeability barriers to the flow. The pale muscovite‐rich zones formed on the downstream side of the vein and the dark biotite‐rich zones mark the upstream side. The alteration couplets formed from mica schist at constant Zr, Ga, Sc, and involved increases in Si, Na, Al and decreases in K, Fe, Mg for pale alteration zones, and inverse alteration within dark zones. The asymmetry of the alteration couplets is best explained by the pressure dependence of mineral–fluid equilibria. These equilibria, in combination with a Darcian flow model for coupled advection and diffusion, and with permeability barriers imposed by the quartz veins, simulate the pattern of both fluid flow and differential, asymmetric metasomatism. The determined vector of fluid flow lies along the regional foliation and is consistent with the known distribution of regional alteration products. The presence of asymmetric alteration zones in rock containing abundant pre‐alteration veins suggests that vein‐rich material may have generally retarded regional fluid flow.     

Reconstruction of palaeo-burial history and pore fluid pressure in foothill areas: a sensitivity test in the Hammam Zriba (Tunisia) and Koh-i-Maran (Pakistan) ore deposits

The burial and pore fluid pressure history of fluorite ore deposits is reconstructed: (i) at Hammam Zriba–Djebel Guebli along the eastern margin of the Tunisian Atlas; and (ii) at Koh‐i‐Maran within the northern part of the Kirthar Range in Pakistan. Both the deposits are hosted by Late Jurassic carbonate reservoirs, unconformably overlain by Late Cretaceous seals. Microthermometric analyses on aqueous and petroleum fluid inclusions with pressure–volume–temperature–composition (PVTX) modeling of hydrocarbon fluid isochores are integrated with kinematics and thermal 2D basin modeling in order to determine the age of mineralization. The results suggest a Cenozoic age for the fluorite mineralization and a dual fluid migration model for both ore deposits. The PVTX modeling indicates that the initial stage of fluorite cementation at Hammam Zriba occurred under fluid pressures of 115 ± 5 bars and at a temperature close to 130°C. At Koh‐i‐Maran, the F3 geodic fluorite mineralization developed under hydrostatic pressures of 200 ± 10 bars, and at temperatures of 125–130°C. The late increase in temperature recorded in the F3 fluorites can be accounted for by rapid rise of hotter fluids (up to 190°C) along open fractures, resulting from hydraulic fracturing of overpressured sedimentary layers.     

TL DATING OF BURNT LITHICS FROM BLOMBOS CAVE (SOUTH AFRICA): FURTHER EVIDENCE FOR THE ANTIQUITY OF MODERN HUMAN BEHAVIOUR*

This paper presents the first TL dates for burnt quartzites and silcretes from the Still Bay layers of Blombos Cave (South Africa). These layers contained engraved ochres and marine shell beads that could be an early manifestation of symbolic and thus ‘modern’ behaviour by the Middle Stone Age humans. The procedure devised to calculate the ages is presented in detail, particularly with regard to internal microdosimetry, because the problems faced in estimating the dose rates require an approach different from the one usually used on flints and sediments. A mean age of 74 ± 5 ka was obtained for five burnt lithics unearthed in the BBC M1 member of the Still Bay layers. This result is in good agreement with both ESR dates on teeth and OSL dates on sediment, and demonstrates the great antiquity of the archaeological remains discovered at Blombos Cave.     

Current Events: The Effects of Electricity Deregulation on State Economies*

Abstract. Panel regressions indicate that state electricity deregulation in the US is associated with higher housing prices, increased activity in the housing market, and lower wages, all of which are consistent with a model of compensating differentials wherein deregulation (which is shown to indeed lower electricity prices) increased the utility of state residents. On the other hand, there is no link between deregulation and job creation.     

The Promised Medicine: Fore Reflections on the Scientific Investigation of Kuru

This paper explores the oral narratives of five South Fore men who assisted with the scientific investigation of kuru. Drawing on the framework of the dramaturgic form of epidemics, the narratives start with childhood memories of the social crisis at the height of the kuru epidemic. With the arrival of the European scientists they build to a climax of optimism over the prospect of a cure for kuru and enhanced personal futures before descending into disillusionment over the scientists' departure and a return to traditional village life.