Comparative Study of Low-Grade Metamorphism in the California Coast Ranges and the Outer Metamorphic Belt of Japan

Abstract

Comparative field and laboratory investigations have been undertaken of representative portions of the Franciscan and Sanbagawa blueschist terranes of the California Coast Ranges and central Shikoku, respectively. Four colored maps at various scales have resulted from this work: the Goat Mountain area at 1:10,000; the San Luis-Pacheco Pass area at about 1:18,300; and the Shirataki and Oboke Districts, both at 1:50,000. In all, modes were measured for nearly 700 thin sections of rocks from the two metamorphic belts; bulk densities for more than half of the corresponding samples were obtained. Also, selected optical and X-ray properties for some minerals from these rocks have been measured. All these data are tabulated elsewhere (Seki and others, 1969), but are summarized graphically in the present report. Chemical data listed in the present paper include 93 conventional gravimetric rock analyses, 121 "wet" chemical analyses of minerals, and 107 electron microprobe analyses of minerals.