Strontium isotopic compositions of late Mesozoic and Early Tertiary acid rocks in Japan
Published:January 01, 1983
The source materials for late Mesozoic and Early Tertiary acid rocks in Japan are examined on the basis of Sr isotopic data. The following are considered as possible source materials: 1) ultrabasic rocks constituting the upper mantle, or basic materials derived from the upper mantle; 2) rocks of andesitic basalt composition probably constituting the uppermost mantle or the lower crust of continental or adjacent regions; 3) rocks of Precambrian or earliest Paleozoic age probably constituting the lower part of the granitic layer of the crust under the Japanese islands; 4) rocks, mainly sedimentary, constituting the Honshu geosyncline.
Comparison of the Sr isotopic data of these four materials with those of the acid rocks indicates that the first two sources are more probable.