Two largest indium ore deposits of 5,000 tons In class in China, Dulong and Dachang mines, studied geochemically. The Dulong deposits have 1000In/Zn value of 4.1 in the average, which is milar to 2.6 of the Changpo-Tongkeng orebody and 3.1 of the Longtaoshan orebody of the Dachang Yet the Dulong ores are depleted in silver and antimony, and enriched in tungsten among the ore while the Dachang ores are rich in silver and antimony similarly to the Toyoha ores occurring in volcanogenic Green Tuff belt in Japan. Concentration of indium in sphalerites is homogeneous in the ores but is strongly banded in the Toyoha ores. It is suggested that the Dulong ore deposits were in a plutonic environment related to S-type ilmenite-series granite, while the Dachang deposits formed at shallower level, related to subvolcanic intrusions. A volcanogenic environment is neces
The Shionofuchi-biotite (Sbi) tephra was found from the Middle Miocene Nanatani Formation at Shionofuchi, Sanjo City, Kamo District, Niigata Prefecture. The Sbi tephra is a crystal-rich coarse tuff layer (9 cm thick) intercalated between the basalt to andesite volcaniclastic rocks and light gray massive mudstone of the Nanatani Formation. This tephra contains plagioclase (oligoclase and bytownite in composition), quartz, sanidine, biotite, opaque minerals and a trace amount of zircon and allanite. Fission-track age of Sbi tephra was determined to be 13.8±0.3 Ma (1σ). This age is consistent with the biostratigraphic data. The Kbi tephra that is correlated to the Muro Pyroclastic Flow Deposit in Kii Peninsula is intercalated in the similar horizon to the Sbi tephra. Furthermore, the lithofacies of the Sbi tephra resembles that of the Kbi tephra. However, according to the inconsistency of plagioclase composition, trace heavy mineral assemblage and uranium contents in zircon, the Sbi tephra is not correlated to the Kbi tephra. Therefore, we have to pay attention to correlate these tephras.
Pollen data from Pleistocene sediments in the GS-SB-1 drilling core, obtained from Shobu Town, Japan, provide a basis on which a pollen biostratigraphy for subsurface geology of the central Kanto plain is constructed. In this study, 150 sediment samples were collected at ca. 2 m intervals from the GS-SB-1 core, which consists mainly of marine and fluvial sediments intercalated with two major Pleistocene marker tephras. The Pleistocene sediments in the GS-SB-1 core were divided into 35 local pollen assemblage zones in an informal nomenclature by a distinctive assemblage of taxa, indicating local environmental conditions as a rudimentary biostratigraphic classification. Each of the marker horizons for Upper, Middle and Lower Pleistocene pollen biostratigraphy was discussed. Moreover, stratigraphy of local pollen assemblage zones was established on the basis of magneto-, litho- and tephrostratigraphy. On the other hand, the SB-Pol-9 and SB-Pol-24 zones in the core are currently a barren interval with the significantly low occurrence of tree and shrub pollen grains. Therefore, the pollen biostratigraphic characters of these zones need to be investigated in other cores further.
We implemented a new analysis strategy for the routine GPS data analysis system of the continuous GPS network of the Geological Survey of Japan, AIST when two new continuous GPS observation stations in Shikoku and Kii Peninsula were installed in 2010. We updated the Bernese GPS software package from Version 4 to 5, and implemented some new methods such as estimation of the troposphere delay gradient as well as the zenith total delay. Comparing the result with that of the previous analysis strategy, we found that the repeatability of the GPS station coordinates were reduced especially in summer, which we inferred was due to the reduction of troposphere delay errors caused by the spatial variation of water vapor that dominated in summer season.