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201.
O. Bruguier D. Bosch R. T. Pidgeon D. I. Byrne L. B. Harris 《Contributions to Mineralogy and Petrology》1999,136(3):258-272
Conventional and SHRIMP U-Pb analyses of zircon, monazite, titanite and apatite from the high grade rocks of the Northampton
Complex in Western Australia provide constraints on the timing of metamorphic processes and deformation events in the northern
Darling Mobile Belt (western margin of the Archean Yilgarn Craton). Paragneisses and mafic volcanics and/or intrusions have
undergone granulite facies metamorphism in a probable extensional tectonic setting prior to formation of W- to NW-verging
folds and thrusts cut by normal shears (interpreted as late collapse structures) during the main deformation event (D1). These structures are folded by open to tight folds with NW-striking axial surfaces developed in a second, NE-SW contractional
event (D2). Zircons from a mafic granulite provide an age of 1079 ± 3 Ma attributed to new zircon growth prior to, or at the peak of
regional granulite facies metamorphism. Metamorphic monazites extracted from a paragneiss yield an identical age of 1083 ± 3 Ma.
The similarity of ages between zircons from the mafic granulite (1079 ± 3 Ma) and monazites from the paragneiss (1083 ± 3 Ma)
is interpreted to reflect fast cooling and/or rapid uplift, which is consistent with thrusting of the gneissic units during
the first deformation event (D1) associated with the onset of retrograde metamorphism. Granitic activity at 1068 ± 13 Ma was followed by intrusion of post-D2 pegmatite (989 ± 2 Ma), which constrains the end of metamorphism and associated deformation. Cooling of the complex to about
500 °C is timed by the apatite age of 921 ± 23 Ma. SHRIMP U-Pb ages of detrital zircons from a paragneiss sample yield a maximum
age of 2043 Ma, with no evidence of an Archean Yilgarn signature. A majority of ages between 1.6 and 1.9 Ga are consistent
with derivation from the Capricorn Orogen on the northern margin of the Yilgarn Craton. Younger detrital zircons with 1150–1450 Ma
ages, however, indicate an additional source that had undergone early Grenvillian igneous or metamorphic event(s) and also
places a maximum age constraint upon deposition. The source of this clastic material may have been from within the southern
Darling Mobile Belt or from Greater India (adjacent to the Northampton Complex in Rodinia reconstructions). This study documents
an extended Grenvillian history, with basin formation, sedimentation, granulite facies metamorphism, contractional tectonics
(two periods with orthogonal directions of shortening) and late pegmatite emplacement taking place between 1150–989 Ma on
the western margin of the Yilgarn Craton. Ages recorded in this study indicate that the proposed global distribution of Grenvillian
belts during assembly of the Rodinia supercontinent should be reassessed to include the Darling Mobile Belt.
Received: 7 January 1998 / Accepted: 10 March 1999 相似文献
202.
Chemical composition of landfill leachate in a karst area with a Mediterranean climate (Marbella, southern Spain) 总被引:2,自引:0,他引:2
I. Vadillo F. Carrasco B. Andreo A. García de Torres C. Bosch 《Environmental Geology》1999,37(4):326-332
Between March 1994 and April 1997, the physical and chemical parameters and chemical composition of the urban solid waste
leachate of the Marbella landfill (southern Spain) were determined. The data obtained show an ammonium and sodium chloride
and bicarbonate type, a pH>7 and high mineralization, effectively described by the following parameters: Na+, K+, NH4
+, Cl– and alkalinity. The chemical composition depends on the rainfall: in dry years, the mineralization and component concentrations
have values as much as double those found in normal rainfall years. After storm events, a major and rapid dilution (within
several hours) is seen in the leachate.
Received: 28 January 1998 · Accepted: 2 June 1998 相似文献