K-Ar geochronology for hydrothermal K-feldspar within plagioclase in a granitic pluton: constraints on timing and thermal condition for hydrothermal alteration.

This study presents the K-Ar geochronology for hydrothermal K-feldspar in plagioclase alteration, including methodology and application to the Toki granite, in central Japan. Borehole samples from the Toki granite were collected and mechanically and chemically processed to separate plagioclase from the rock and remove bulk impurities. The sample fraction of cleaned plagioclase powder was further processed to a smaller size fraction, allowing separation of the altered K-feldspar from the plagioclase host. The resulting K-feldspar represented the hydrothermal alteration product and was characterized crystallographically as microcline, and its K-Ar ages were measured. The results of the K-Ar dating and petrographic characterization indicated that in this setting, plagioclase alteration occurred through a combination of solid-state replacement and dissolution-precipitation processes. The K-feldspathization age enables constraint of the temporal conditions of the solid-state replacement process to 62.2 ± 1.4 Ma. The time-temperature (t-T) path of the sampling site is an effective tool for determining both the timing and thermal conditions of the hydrothermal microcline formation in plagioclase alteration. The combination of the t-T path and the microcline K-Ar age provides formation temperatures of about 307-325 °C. The timing and thermal conditions of solid-state replacement (62.2 ± 1.4 Ma and 325-307 °C) indicate an older age and a higher temperature than those of dissolution-precipitation (59.2 ± 1.4 Ma and 305-290 °C: Yuguchi et al., 2019A). The plagioclase alteration consists of serial processes from solid-state replacement to dissolution-precipitation. Addition of the thermal conditions and timing into petrography have implications for the sequential phenomenal variation in granite.

Microdiamond in a low-grade metapelite from a Cretaceous subduction complex, western Kyushu, Japan.

Microdiamonds in metamorphic rocks are a signature of ultrahigh-pressure (UHP) metamorphism that occurs mostly at continental collision zones. Most UHP minerals, except coesite and microdiamond, have been partially or completely retrogressed during exhumation; therefore, the discovery of coesite and microdiamond is crucial to identify UHP metamorphism and to understand the tectonic history of metamorphic rocks. Microdiamonds typically occur as inclusions in minerals such as garnet. Here we report the discovery of microdiamond aggregates in the matrix of a metapelite from the Nishisonogi unit, Nagasaki Metamorphic Complex, western Kyushu, Japan. The Nishisonogi unit represents a Cretaceous subduction complex which has been considered as an epidote-blueschist subfacies metamorphic unit, and the metapelite is a member of a serpentinite mélange in the Nishisonogi unit. The temperature condition for the Nishisonogi unit is 450 °C, based on the Raman micro-spectroscopy of graphite. The coexistence of microdiamond and Mg-carbonates suggests the precipitation of microdiamond from C-O-H fluid under pressures higher than 2.8 GPa. This is the first report of metamorphic microdiamond from Japan, which reveals the hidden UHP history of the Nishisonogi unit. The tectonic evolution of Kyushu in the Japanese Archipelago should be reconsidered based on this finding.

The effects of long-term herbal treatment for pediatric AIDS.

This paper presents our long-term (1992-2000) treatment of pediatric Acquired Immune Deficiency Syndrome (AIDS) patients (maximum 100 children, last three years 65) using native herbal remedies in a voluntary medical assistance program in Constanta, Romania. We primarily report the progress of 10 children at a facility called the "House of Tomorrow" and three other facilities. The long-term (8 years and 8 months) treatment contributed to a drop of the amount of Human Immunodeficiency Virus Ribonucleic Acids (HIV-RNA) below the measurable level for 9 out of 10 patients at the "House of Tomorrow." Furthermore, the treatment led to preservation and increase of the cluster of differentiation (CD4) count, a remarkable decrease in mortality rate, as well as the maintenance of a good quality of life. It took one to three years for the beneficial effects of the treatment to emerge. No side-effects were recognized either clinically or biochemically, nor was there any emergence of drug-resistant strains of HIV as seen with anti-HIV chemical treatments. This paper also refers to which herbal remedies were used and their general mechanism of action.