The Hijikai granodioritic complex is a stock-like zoned pluton that has been intruded by Cretaceous Hiroshima granites of the San’yo Belt. The complex is compositionally zoned from a mafic rim to a more felsic core, and is divided into following four rock types: tonalite, granodiorite, hornblende biotite granite and biotite granite. The tonalite changes gradually to hornblende biotite granite via granodiorite, while the biotite granite intrudes into the hornblende biotite granite. Continuous compositional trends of all types of the granitoids on Harker variation diagrams suggest that the granitoids were formed by crystal differentiation from a magma. The variations of Rb and Sr concentrations imply the change in fractionation phases from the assemblage of hornblende and plagioclase to that of K-feldspar and plagioclase during crystallization. The differences in the compositional trends of Na2O, K2O, Rb and Sr between the Hijikai gnanitoids and the Hiroshima granites suggest that both were derived from different magma sources. Two stock-like zoned plutons, Ukan and Myoken-zan, are distributed near the Hijikai complex. The compositional similarity between the Hijikai and the Ukan granitoids suggests that both were derived from similar magma sources, while the Myoken-zan granitoids have different compositional trend of MgO and Na2O compared with them.
Amphibolite and clinopyroxene amphibolite occurred as xenoliths in monzodiorite dikes that intruded into limestone at Fuka, Okayama Prefecture. The amphibolite xenolith is composed mainly of amphibole and plagioclase. The clinopyroxene amphibolite xenolith is composed mainly of clinopyroxene, biotite, amphibole and plagioclase. The amphibole also occurred around the prehnite, grossular, clinopyroxene and calcite bearing veinlets that were formed in the clinopyroxene amphibolite xenoliths. The microprobe analyses of the amphiboles gave XMg=0.53−0.58, 3.3−4.6 wt% TiO2 and 1.3−2.1 wt% K2O. The compositions corresponded to kaersutite-pargasite.
This report describes our recent development that mainly aims at the quantitative determination of hydrogen concentration in melt inclusions confined in minerals. The method is based on the proton-proton elastic scattering at 20 MeV. Since the stopping power of protons at 20 MeV is very small in materials as silicates, protons pass through a 200 μm thick sample without appreciable energy loss. It is feasible, therefore, to carry out non-destructive hydrogen analysis of melt inclusions with sizes in the range from a few tens to approximately 200 micrometers. Besides the depth profile of hydrogen, a map of the three-dimensional hydrogen concentration is observable using a scanning microbeam. An example is presented on a melt inclusion in quartz from pyroclastic rocks collected at Enda, Zaoh-machi, Miyagi Prefecture, Japan.
Recently mineral scientists have paid attention to the neutron scattering, because some intense pulsed neutron sources have been constructed or in planning in the world. In Japan, the High Energy Accelerator Research Organization (KEK) and the Japan Atomic Energy Research Institute (JAERI) have jointly constructed a 1 MW pulsed neutron source (JSNS) at Tokai, Ibaraki. The neutron and the x-ray diffraction should provide complementary information each other because of their physical properties. For example, light elements like hydrogen are almost invisible for x-ray and it is difficult for x-ray to distinguish neighboring elements in the Periodic Table such as Mg, Al and Si, which are major elements in geological materials and often show interesting order-disorder relating phenomena. However, neutron expects to provide useful information about those invisible problems of x-ray since the scattering cross-section of neutron is independent of the atomic numbers. In this paper, we will give an overview of elastic neutron scattering and give some ideas of mineral physics at high pressure and high temperature. In addition, we will shortly introduce the JSNS and our proposal of a high pressure/temperature material science station in the JSNS.