Chapter 39: DISCRIMINATING AMONG VOLCANIC TEMPER SANDS IN PREHISTORIC POTSHERDS OF PACIFIC OCEANIA USING HEAVY MINERALS.

Many volcanic sand tempers used for the fabrication of prehistoric ceramics in Pacific Oceania are beach placer sands with heavy mineral contents that reflect the phenocryst mineralogy of bedrock on the islands where pottery was made. Island groups within the region of ceramic cultures extending from western Micronesia to western Polynesia include hotspot, arc, postarc, and backarc geotectonic settings. The abundance of opaque minerals is governed by intensity of placering and is not diagnostic of geotectonic temper class, but differing proportions of ferromagnesian silicate mineral grains faithfully reflect island provenance. Clinopyroxene is the most abundant non-opaque heavy mineral in nearly all tempers of volcanic derivation. Hotspot tempers are marked by relative abundance of olivine (>25%), which also occurs in subordinate amounts in selected arc and postarc tempers. Hornblende accompanies clinopyroxene in varying proportions in other arc and postarc tempers, and orthopyroxene accompanies clinopyroxene in arc tempers from New Britain and Tonga. Relative proportions of heavy mineral species in Oceanian placer tempers correlate with the nature of restricted bedrock sources on individual islands, and serve as diagnostic evidence for temper origins wherever pottery was transported between islands. [ABSTRACT FROM AUTHOR]