Abstract
The ultramafic masses in this district intrude into the green rocks of the Motai formation and the slate of the Tobigamori formation. The green rocks of the Motai formation are partly composed of the glaucophane rocks.
Three common hornblendes were separated from the metagabbro and amphibolites, which associate with the serpentain masses, and analysed chemically. The chemical analyses and the atomic ratios are shown in Table 1. The results plotted on the Hallimond's triangle diagram indicates that the hornblendes of the Takozu district are similar in composition to that of the Miyamori and Abukuma districts.
Optical and X-ray powder data are shown in Table 2 and 3. The observed mineral parageneses of these rocks are
Common hornblende-albite-epidote-biotite-sphene
Common hornblende-oligoclase-epidote-chlorite-sphene
Lastly, petrogenesis of metagabbro and amphibolite is briefly discussed from the views of mineral paragenesis and mineralogical properties of the hornblendes.
It may be that these rocks were retrogressively formed from gabbroic rocks in the condition of epidote amphibolite and amphibolite facies.
