Manus Islands

Table 98.3 Expenditure on offshore asylum seeker management on Nauru and Manus Island to end May 2002...

Manus Basin is a back-arc basin located north of the New Britain island arc that consists of NE-SW trending ridge segments offset by transform faults. On the Manus Spreading Center in central Manus Basin the Vienna Woods hydrothermal field consists of a 300 m-diameter sulfide mound with an extensive foresf of active and inactive sphalerite-barite-rich, sulfide-sulfate-oxide chimneys up to 15 m-long atop it. Vent fluids from one of the active chimneys reach temperatures as high as 302°C. In the eastern Manus Basin, two important hydrothermal fields are known. The PACMANUS field includes discontinuous sulfide occurrences over a 3 by 0.8 km area and active venting of unknown nature. Volcanic rocks are andesitic to rhyodacitic. 

Ra, respectively Moreira et al. 1995 Sarda et al. 2000), the Southwest Indian Ridge near Bouvet Island (14.9 Ra Kurz et al. 1998) and the Manus Basin back-arc spreading center (15.1 Ra Shaw et al. 2001). In each of these areas, the high He/ tae signal can be attributed to introduction of high He/ He material from a nearby mantle hotspot. The apparent upper limit to the measured He/ He in these cases is usually presumed to stem from dilution with ambient upper mantle having He/" He between 7 and 9 Ra. 

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