Transition of metamorphic series from the Kyanite- to andalusite-types in the Altai orogen, Xinjiang, China: Evidence from petrography and calculated KMnFMASH and KFMASH phase relations

Metamorphic zones in the Chinese Altai orogen have previously been separated into the kyanite- and andalusite-types, the andalusite-type being spatially more extensive. The kyanite-type involves a zonal sequence of biotite, garnet, staurolite, kyanite, sillimanite and, locally, garnet–cordierite zones. The andalusite-type zonal sequence is similar: it includes biotite, garnet and staurolite zones at lower-T conditions and sillimanite and garnet–cordierite zones at higher-T conditions, but additionally contains staurolite–andalusite and andalusite–sillimanite zones at intermediate-T conditions. As relic kyanite-bearing assemblages commonly persist in the staurolite–andalusite, andalusite–sillimanite and sillimanite zones, it is not clear that the distinction is valid. On the basis of a reevaluation of phase relations modelled in KMnFMASH and KFMASH pseudosections, kyanite and andalusite-bearing rocks of the Chinese Altai orogen record, respectively, the typical burial and exhumation history of the terrane. Mineral assemblages distributed through the various zones reflect a mix of portions of the ambient P–T array and the effects of evolving P–T conditions. The comparatively low-T biotite, garnet and staurolite zones mostly preserve kyanite-type peak assemblages that only experienced minor changes during exhumation. Rocks in the comparatively high-T sillimanite and garnet–cordierite zones are dominated by mineral assemblages of a transitional sillimanite type, having formed by the extensive modification of earlier higher pressure assemblages during exhumation. Only rocks in the intermediate-T kyanite and probably some lower sillimanite zones were clearly recrystallized by late stage andalusite metamorphism, producing the staurolite–andalusite and andalusite–sillimanite zones. This andalusite metamorphism could not reach an equilibrium state because of limited fluid availability.     

Combining microsimulation and spatial interaction models for retail location analysis

Although the disaggregation of consumers is crucial in understanding the fragmented markets that are dominant in many developed countries, it is not always straightforward to carry out such disaggregation within conventional retail modelling frameworks due to the limitations of data. In particular, consumer grouping based on sampled data is not assured to link with the other statistics that are vital in estimating sampling biases and missing variables in the sampling survey. To overcome this difficulty, we propose a useful combination of spatial interaction modelling and microsimulation approaches for the reliable estimation of retail interactions based on a sample survey of consumer behaviour being linked with other areal statistics. We demonstrate this approach by building an operational retail interaction model to estimate expenditure flows from households to retail stores in a local city in Japan, Kusatsu City.      

Fractal travel time estimates for dispersive contaminants

Alternative fractional models of contaminant transport lead to a new travel time formula for arbitrary concentration levels. For an evolving contaminant plume in a highly heterogeneous aquifer, the new formula predicts much earlier arrival at low concentrations. Travel times of contaminant fronts and plumes are often obtained from Darcy's law calculations using estimates of average pore velocities. These estimates only provide information about the travel time of the average concentration (or peak, for contaminant pulses). Recently, it has been shown that finding the travel times of arbitrary concentration levels is a straightforward process, and equations were developed for other portions of the breakthrough curve for a nonreactive contaminant. In this paper, we generalize those equations to include alternative fractional models of contaminant transport.     

The formation of mud patches by non-linear diffusion

Deposits of mud on an otherwise sandy continental shelf floor commonly occur in the form of patches a few hundred meters in size. A model for the formation of these patches is proposed that is based on a resuspension mechanism that is a non-linear function of the percentage of fines in the surficial sediment. A diffusion equation governing the time evolution of the percentage fines is derived which for a certain range of fine sediment concentrations becomes unstable. Numerical solution of this equation shows that the spatial distribution of fine sediment breaks into two components in a manner qualitatively similar to observed mud patches.     

Water filtration through reflective microtidal beaches and shallow sublittoral sands and its implications for an inshore ecosystem in Western Australia

Volumes of seawater filtered through the intertidal zone were measured on three modally reflective microtidal beaches in Western Australia. The filtered volumes were large, 19 m³ m^?1 day^?1 and 73 m³ m^?1 day^?1 on two ‘clean’ beaches but only 0·4 m³ m^?1 per tidal cycle on a beach covered in kelp and seagrass wrack. The mean residence times of this water in the interstitial system and its percolation paths were both short, 1–7 h and 2–5 m respectively. Water input was greater across a beach cusp horn than across a cusp embayment. Most input occurred in the upper swash zone where the water table was less than 20 cm deep. Tidal variations in input volumes were evident even with tide ranges of only 20 cm. The inshore zone off these beaches filters on average 0·07 m³ m^?2 day^?1 at an average depth of 5·5 m under 0·4 m waves of 6·5 s duration. The importance of these procedures in the mineralization of organic materials and the regeneration of nutrients for an inshore ‘lagoon ecosystem’ is estimated and discused.