Orientation studies indicate that stream-sediment geochemistry is a potentially useful exploration tec~ique in the Kepala Burung region of Irian Jaya, Indonesia. Previously located uranium anomalies and small zones of known base-metal sulphide. mineralisation, are reflected in anomalous concen• trations of these elements in•the stream sediments.
Geologists collected 47 st ream-sediment samples from an area of about 3500 km2 in northeastern Kepala•Burung. All samples.were submitted to AMDEL, where each was analysed for 23 elements.
Cumulative :frequency curves.have been used•to_distin~ish between
background and anomalous populations for 14 of the 23 eIements ,
' . . . '
Spatial dist r.ihut ions of element concentrations iridicato the

presence of two geochemical. provinces ~ithin the region:• (1) an. eastern province of volcanic.rocks characterised by.high copper~ nickel, and mangan• ese, and low arsenic, uranium., and lead concentrations, reiative to (2) a western province of sediments and low-grade metamorphics intruded by granites. The,•two 'prov inces are separated by a major fault.•
Size fraction a11~ly.sis .indica~es that future stream-sediment. surveys should use the -80 mesh fraction.
Anomalous uranium concentrations associated with granites appear to
be derived from urani.um-bear ing accessory mmerajs such as zircon, monazite., xenot ime , thorite., and allanite (rather than. from common ore-forming urani.ua • minerals)., and are usually accompanied by high. thorium and cerium concentra• tions. Values for thorium and cerium can thus be used to screen uranium anomalies •

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