Early extension in the Late Archaean northeastern Eastern Goldfields Province,Yilgarn Craton,Western Australia     

J. R. McIntyre  J. E. Martyn 《Australian Journal of Earth Sciences》2013,60(6):975-992

A series of linked extensional detachments, transfer faults, and sediment- and volcanic-filled half-grabens that pre-date regional folding are described in the Late Archaean Margaret anticline, Eastern Goldfields Province, Yilgarn Craton, Western Australia. Coeval structures and rock units include layer-parallel extensional detachments, transfer faults (high-angle rotational faults rooted in the detachments and linking layer-parallel shear zones with varying amounts of extension); felsic intrusions, either as granitoids emplaced in or below the detachments, or as fine-grained intrusive bodies emplaced above the detachments and controlled by the high-angle faults; and half-grabens controlled by the high-angle faults and filled with clastic sedimentary and volcanic rocks. At least 1500 m of section is excised across the detachments. The detachments and high-angle faults are folded by the east-northeast regional compression that formed the Margaret anticline. Extensional deformation in the Margaret anticline is correlated with the regionally recognised felsic magmatism and associated volcanic and volcaniclastic basin fill dated at approximately 2685–2670 Ma across the Eastern Goldfields Province. This suggests the extensional event was province-wide and post-dated initial greenstone deposition (at around 2705 Ma) but pre-dated regional compressive deformation. We suggest the extension is the result of a thermal anomaly in the crust, generated by the insulating effect of a thick pile (of the order of 10 km or greater) of mafic and ultramafic volcanic rocks on precursor Archaean felsic crust. The thermal anomaly has generated renewed production of felsic and mafic volcanic rocks, coeval with uplift and extension in the upper crust.  相似文献   

Regionalisation of hydrological responses under land-use change and variable data quality     

S. Visessri  N. McIntyre 《水文科学杂志》2013,58(2):302-320

ABSTRACT

Estimating river flows at ungauged sites is generally recognised as an important area of research. In countries or regions with rapid land development and sparse hydrological gauging networks, three particular challenges may arise—data scarcity, data quality, and hydrological non-stationarity. Using data from 44 gauged sub-catchments of the upper Ping catchment in northern Thailand from the period 1995–2006, three relevant flow response indices (runoff coefficient, base flow index and seasonal elasticity of flow) were regionalised by regression against available catchment properties. The runoff coefficient was the most successfully regionalised, followed by base flow index and lastly the seasonal elasticity. The non-stationarity (represented by the differences between two 6-year sub-periods) was significant both in the flow response indices and in land use indices; however relationships between the two sets of indices were weak. The regression equations derived from regionalisation were not helpful in predicting the non-stationarity in the flow indices except somewhat for the runoff coefficient. A partly subjective data quality scoring system was devised, and showed the clear influence of rainfall and flow data quality on regionalisation uncertainty. Recommendations towards improving data support for hydrological regionalisation in Thailand include more relevant soils databases, improved records of abstractions and investment in the gauge network. Widening of the regionalisation beyond the upper Ping and renewed efforts at using remotely sensed rainfall data are other possible ways forward.