Barium-rich phlogopite occurs in a mantle derived xenolith incorporated into the Upper Canada Mine kimberlite, Ontario, Canada. The phlogopite is characterized by high BaO (up to 4.3 wt.%) and Na₂O (up to 2.2 wt.%) and extremely low TiO2 (0.02 wt.%) contents with a relatively high ratio (0.95) of Mg/(Mg+Fe). The chemical characteristics distinguish the phlogopite from Ba-rich micas reported from various alkalic mafic-ultramafic igneous rocks and
suggest that the phlogopite has been formed by mantle metasomatism involving Ba- and alkali-rich, Ti-poor hydrous fluids. The Ba content of phlogopite in this study is about five times higher than that of phlogopite previously reported from mantle derived xenoliths. A compilation of data suggests a distinct correlation between Ba and K in mantle derived xenoliths and various continental volcanic rocks (alkali basalts, ultrapotassic basic rocks, lamprophyres, lamproites, and kimberlites). A range of Ba/K in the xenoliths and-the volcanic rocks examined is comparable with that of mantle phlogopite, suggesting that phlogopite may be a principal reservoir for Ba as well as K in the upper mantle source regions.

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The Rb-Sr isochron ages were determined for the granitic rocks in the Tsukuba district, Japan. The Coarse-grained granite gives a mineral isochron age of 60.2 ± 0.4 Ma and whole rock isochron age of 61.6 ± 4.3 Ma. The Porphyritic granodiorite has a mineral isochron age of 59.5 2.7 Ma. Pegmatite dikes in the Yamanoo area, which are the products of final stage granitic activity in the Tsukuba district, yield whole rock and mineral isochron ages of 59.9 ± 4.0 Ma and 58.3 ± 2.3 Ma, respectively.
The Rb-Sr ages in this study and published K-Ar mineral ages for the granitic rocks in the Tsukuba district are concentrated in very narrow range, mostly 59-62 Ma, irrespective of intrusive stages, indicating that the magmatic activities in the Tsukuba district occurred during short time interval (less than 3 Ma). Concordance of the Rb-Sr whole rock age and K-Ar mineral ages suggests that the granitic magma cooled rapidly after emplacements.

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Three samples of interstratified mica/smectite were found in the argillized veins in the hydrothermally altered tuff and andesite in the Ten-ei district Fukushima Prefecture. The types of interstratifications of these minerals are g=2, g=3 and g ?? 3, and the proportions of the expandable layers are approximately 30%, 5% and 2%, respectively. Chemical analyses for these minerals, argillized rocks including these minerals and their wall rocks show the chemical compositions of these minerals considerably differ, with respect to Si/Al ratio in the tetrahedral layer, number of Fe in the octahedral layer and Na in the interlayer, and these differences of chemical compositions seem to be not related to those of their wall rocks. This result probably suggests the variations of the chemical compositions were influenced by those of hydrothermal solutions during the formation processes of these minerals.

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Use of spread sheet program is strongly advocated for many geological calculations such as mineral formula and CIPW norm because of the ease of programming and ability of performing “what if” calculations without reentering all the data.

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