We present oxygen and carbon isotope ratios and the morphological structure of the cultured freshwater pearl mussel (Hyriopsis sp., Unionidae) shell and pearl. The number of first-order fluctuations of δ18O of the outer shell layer along the maximum growth axis was consistent with the number of cultured years. The dominant factor
controlling annual δ18O fluctuations was water temperature with a minor contribution from the variation in δ18O of ambient water, especially during the rainy season. The δ13C values were approximately constant throughout the life of the mussel, suggesting that the contributions of body size to
δ13C of the shell were minor. We observed nine distinct disturbance rings on the outer surface of the shell. Five rings coincided
with the five winter peaks of the δ18O profile, indicating winter growth cessation below approximately 10°C, probably because of either inactive growth at low
water temperatures or reproduction. Summer disturbance rings were not observed in all years. Moreover, some summer rings showed
discontinuity in the inner structure. These findings suggest that summer growth cessation may be caused by occasional events
such as heavy rains, as the decrease of dissolved oxygen concentration. The δ18O profile and shell structures indicated that shell aragonite was precipitated at close to equilibrium conditions with respect
to the oxygen isotope composition of the ambient water. Hyriopsis sp. shells can potentially be used for reconstruction of past hydrologic conditions. The δ18O of a pearl indicated that calcification occurred over a temperature range of at least 13–23°C. The optimal temperature for
pearl calcification in this species is lower than that for marine pearl calcification. 相似文献
To clarify the beneficial roles of naturally occurring organic ligands on the growth of phytoplankton in newly upwelled water,
phytoplankton culture experiments using disphotic zone water were conducted to discriminate between the effects of EDTA in
the detoxification of certain toxic metal ions and increasing the availability of essential metals. Culture media were prepared
by adding EDTA and Chelex-100, separately or in combination, to disphotic zone water samples. Our proposed working hypothesis
is that phytoplankton growth can be enhanced by removing toxic metal ions from culture media by Chelex-100 and by detoxification
of toxic metal ions or increasing the availability of essential metals by EDTA. A shortening of the lag period and an increase
of the specific population growth rate were clearly observed after the addition of Chelex-100; nd EDTA. The effects of EDTA
were more considerable than those of Chelex-100; a 17 to 44% in shortening the lag period and a 35 to 56% increase in the
growth rate, when comparing the effects of Chelex-100 with those of EDTA. The similar effects of removing toxic metal ion
by Chelex-100 as those of detoxification by EDTA suggested that EDTA has a role not only of detoxification but also of increasing
the availability of essential metals. The present study suggests that the low productivity in newly upwelled water observed
by Barber and Ryther (1969) can be ascribed to both toxic metal ions and a lack of available forms of essential metals because
of their low contents of free natural organic ligands. 相似文献
The regional and local variations in the composition of the wolframite series associated with the ilmeniteseries and magnetite-series granitoids in the Inner Zone of SW Japan were investigated using X-ray diffraction and microprobe analyses. It is concluded that the variation in Mn/Fe ratios in the source materials (granitic magmas in most cases) is the dominant factor controlling the regional variation in the wolframite compositions, while, as exemplified by the Kaneuchi mine, Kyoto Prefecture, the wallrock chemistry and pH of ore fluids are responsible for the local variation within a single vein system. Within a fresh euhedral crystal from the mine, only slight compositional variation of less than 3 mole% MnWO4 is found in the form of oscillatory zoning. This study, combined with the fluid inclusion research, indicates that the wolframite compositions (Mn/Fe ratios) cannot be used as a geothermometer. 相似文献
A corundum-bearing mafic rock in the Horoman Peridotite Complex, Japan, was derived from upper mantle conditions to lower crustal conditions with surrounding peridotites. The amphiboles found in the rock are classified into 3 types: (1) as interstitial and/or poikilitic grains (Green amphibole), (2) as a constituent mineral of symplectitic mineral aggregates with aluminous spinel at grain boundary between olivine and plagioclase (Symplectite amphibole) and (3) as film-shaped thin grains, usually less than 10 μm in width, at grain boundary between olivine and clinopyroxene (Film-shaped amphibole). The Film-shaped amphibole is rarely associated with orthopyroxene extremely low in Al2O3, Cr2O3 and CaO (Low-Al OPX). These minerals were formed by infiltration of SiO2- and volatile-rich fluids along grain boundaries after the rock was recrystallized at olivine-plagioclase stability conditions, i.e. the late stage of the exhumation of the Horoman Complex.
Chondrite-normalized rare earth element patterns and primitive mantle-normalized trace-element patterns of the Green amphibole and clinopyroxene are characterized by LREE-depleted patterns with Eu positive and negative anomalies of Zr and Hf. These geochemical characteristics of the constituent minerals were inherited from original whole-rock compositions through a reaction involving both pre-existing clinopyroxene and plagioclase. We propose that the fluids were originally rich in a SiO2 component but depleted in trace-elements. Dehydration of the surrounding metamorphic rocks in the Hidaka metamorphic belt, probably related to intrusion of hot peridotite body into the Hidaka crust, is a plausible origin for the fluids. 相似文献
Infrared spectroscopy and ion micro-probe measurements showed that the major constituent minerals of eclogites from the Kokchetav massif, which have been subducted to 180 km depths, contain significant amounts of water up to 870 ppm H2O (by weight) in omphacite, 130 ppm H2O in garnet and 740 ppm H2O in rutile. Omphacite shows three hydroxyl absorption bands at 3440–3460, 3500–3530 and 3600–3625 cm− 1, garnet has a single band at 3580–3630 cm− 1 and rutile has a single sharp band at 3280 cm− 1. The hydroxyl absorbance at these wavenumbers changes with the crystal orientation in polarized infrared radiation, indicating that the water is structurally incorporated in these minerals. The water contents in omphacite and garnet increase systematically with the metamorphic pressure of the host eclogites. The partitioning coefficient of the water content between coexisting garnet and omphacite is similar in different eclogites, DGrt/Omp0.1–0.2, but decreases slightly at high pressure. Based on the mineral proportions of the eclogites, we estimate bulk-rock water content in the eclogites ranging from 3070 to 300 ppm H2O (by weight). Although hydrous minerals are absent in the diamond-grade eclogite (60 kbar and 1000 °C), trace amounts of water are incorporated in the nominally anhydrous minerals such as omphacite and garnet. The presence of significant water in these minerals implies that the subducting oceanic crust can transport considerable amounts of water into the deep upper mantle beyond the stability of hydrous minerals. Such water may be stored in the deep upper mantle and have an important influence on dynamics in the Earth's interior. 相似文献
The oxygen three-isotope systematics of 36 chondrules from the Allende CV3 chondrite are reported using high precision secondary ion mass spectrometer (CAMECA IMS-1280). Twenty-six chondrules have shown internally homogenous Δ17O values among olivine, pyroxene, and spinel within a single chondrule. The average Δ17O values of 19 FeO-poor chondrules (13 porphyritic chondrules, 2 barred olivine chondrules, and 4 chondrule fragments) show a peak at −5.3 ± 0.6‰ (2SD). Another 5 porphyritic chondrules including both FeO-poor and FeO-rich ones show average Δ17O values between −3‰ and −2‰, and 2 other FeO-poor barred olivine chondrules show average Δ17O values of −3.6‰ and 0‰. These results are similar to those for Acfer 094 chondrules, showing bimodal Δ17O values at −5‰ and −2‰. Nine porphyritic chondrules contain olivine grains with heterogeneous Δ17O values as low as −18‰, indicating that they are relict olivine grains and some of them were derived from precursors related to refractory inclusions. However, most relict olivine grains show oxygen isotope ratios that overlap with those in homogeneous chondrules. The Δ17O values of four barred olivine chondrules range from −5‰ to 0‰, indicating that not all BO chondrules plot near the terrestrial fractionation line as suggested by previous bulk chondrule analyses. Based on these data, we suggest the presence of multiple oxygen isotope reservoirs in local dust-rich protoplanetary disk, from which the CV3 parent asteroid formed.A compilation of 225 olivine and low-Ca pyroxene isotopic data from 36 chondrules analyzed in the present study lie between carbonaceous chondrite anhydrous mineral (CCAM) and Young and Russell lines. These data define a correlation line of δ17O = (0.982 ± 0.019) × δ18O − (2.91 ± 0.10), which is similar to those defined by chondrules in CV3 chondrites and Acfer 094 in previous studies. Plagioclase analyses in two chondrules plot slightly below the CCAM line with Δ17O values of −2.6‰, which might be the result of oxygen isotope exchange between chondrule mesostasis and aqueous fluid in the CV parent body. 相似文献