MINERALOGICAL-GEOCHEMICAL PECULIARITIES OF HYDROTHERMAL SULFIDE ORES OF MANUS BASIN (BISMARC SEA)

The paragenetic mineral associations and the sequence of mineral preci pitation from the hydrothermal chimney of the typical backark basin ha ve been determined by complex mineralogical, chemical and isotope meth ods. The distinguishing feature of Manus basin ores is high abundance of Zn-rich minerals (sphalerite, wurtzite, Fe-sphalerite). The assembl age of Fe-sphalerite - galena - Ag-sulfursalts has been marked. This a ssociation is not typical for usual hydrothermal systems of the mid-oc ean-ridges. Isotopic composition of sulfur (deltaS-34 = 3.5 parts per thousand) in the sulfides from Manus chimney corresponds to the middle temperature of ''sphalerite'' stage of the mineral formation. It is s upposed that comparatively acid rocks of I.A.T. or may be sedimentary deposits were the main source of the metals in minerals from Manus bas in.