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1.
Partitioning of Ni2+, Co2+, Fe2+, Mn2+ and Mg2+ between olivine and silicate melts: compositional dependence of partition coefficient 总被引:1,自引:0,他引:1
Eiichi Takahashi 《Geochimica et cosmochimica acta》1978,42(12):1829-1844
Partitioning of Ni2+, Co2+, Fe2+, Mn2+ and Mg2+ between olivine and silicate melts has been determined near the join (Mg0.5·-Fe0.5)2SiO4-K2O 4SiO2 and for seven different basaltic compositions. The experiments were made at 1 atm total pressure, 1500-1100°C, and under moderate to reducing oxygen fugacities. The concentration factor, defined as KMO = (MO)ol/(MO)liq (molar ratio), increases markedly for all the cations studied as the olivine component of the liquid decreases. Much of the increase in KMO is considered as due to the compositional effect of the coexisting liquid: the temperature effect on KMO is probably opposite to the compositional effect (KMO decreases as temperature decreases).The partition coefficient KMO-MgO = (MO/MgO)ol/(MO/MgO)liq for the reaction, Mol2+ + Mgliq2+ = Mliq2+ + Mgol2+. is relatively constant over a wide range of SiO2 content of the liquid, except in the case of Ni2+. The partition coefficients have similar ranges both in synthetic and natural rock systems: KNiO-MgO = 1.8–3.0, KCoO-MgO = 0.6–0.8, KFeO-MgO = 0.27–0.38, and KMnO-MgO = 0.23–0.32. There is a systematic variation in the partition coefficient KMO-MgO with the composition of liquid; KMO-MgO increases with increasing SiO2 content of melt. The partition coefficients for Co2+, Fe2+ and Mn2+ are useful to test the equilibration of olivine with magma of a wide compositional range. 相似文献
2.
Initial 87Sr/86Sr ratios, major and trace element compositions have been determined for the Paleogene granitic rocks in the Tsukuba district, Japan. Isotopic ages strongly suggest that the granitic rocks (seven units) were continuously emplaced and solidified during a short time interval. Initial 87Sr/86Sr ratios for seven granitic units vary from 0.7082 to 0.7132, while sedimentary and metasedimentary country rocks have ratios at the time of granitic magma emplacement ranging from 0.7149 to 0.7298. Continuous linear arrays for the granitic rocks in the diagrams of initial 87Sr/86Sr ratios versus some chemical parameters can be explained by either of following two processes. One is the assimilation — fractional crystallization (AFC) process between the parental magma (SiO2 of 68% and initial ratio of 0.7078) and sedimentary country rocks, and the other is magma mixing process between above parental magma and sediment derived acidic magma (melt) (SiO2 of 75%). The high initial ratios (0.7078–0.7098) for basic rocks such as gabbro or diorite in the Tsukuba district and the similar characteristics observed in the rocks of Ryoke belt (SW Japan) suggest that the parental magma had the same source region as the basic rocks, probably the lower crustal source. 相似文献
3.
4.
Yangting Lin Ahmed El Goresy Sen Hu Jianchao Zhang Philippe Gillet Yuchen Xu Jialong Hao Masaaki Miyahara Ziyuan Ouyang Eiji Ohtani Lin Xu Wei Yang Lu Feng Xuchao Zhao Jing Yang Shin Ozawa 《Meteoritics & planetary science》2014,49(12):2201-2218
Two petrographic settings of carbonaceous components, mainly filling open fractures and occasionally enclosed in shock‐melt veins, were found in the recently fallen Tissint Martian meteorite. The presence in shock‐melt veins and the deuterium enrichments (δD up to +1183‰) of these components clearly indicate a pristine Martian origin. The carbonaceous components are kerogen‐like, based on micro‐Raman spectra and multielemental ratios, and were probably deposited from fluids in shock‐induced fractures in the parent rock of Tissint. After precipitation of the organic matter, the rock experienced another severe shock event, producing the melt veins that encapsulated a part of the organic matter. The C isotopic compositions of the organic matter (δ13C = ?12.8 to ?33.1‰) are significantly lighter than Martian atmospheric CO2 and carbonate, providing a tantalizing hint for a possible biotic process. Alternatively, the organic matter could be derived from carbonaceous chondrites, as insoluble organic matter from the latter has similar chemical and isotopic compositions. The presence of organic‐rich fluids that infiltrated rocks near the surface of Mars has significant implications for the study of Martian paleoenvironment and perhaps to search for possible ancient biological activities on Mars. 相似文献
5.
Shinya Iwasaki Kozo Takahashi Yusuke Ogawa Seiichiro Uehara Christoph Vogt 《Journal of Oceanography》2014,70(3):241-249
Accurate knowledge of the extent of biogenic opal preservation in marine sediment cores is important for paleoceanographic reconstructions. The alkaline leaching method is widely employed for %biogenic opal analysis due to its ease and speed. In this study, a revised method for measuring %biogenic opal in sediment from arctic coring expedition samples was suggested. The studied middle Eocene sediments from the central Arctic Ocean presented a problem in insufficiently leaching biogenic opal with a Na2CO3 solution. Based on XRD analysis, it was suggested that such an alkaline resistance results from slight diagenesis of biogenic opal. In order to solve this problem, an alkaline leaching method utilizing a 2 M NaOH solution was suggested for the accurate measurement of %biogenic opal in the Eocene sediments from the central Arctic. Furthermore, dissolution rates from lithogenic matter by NaOH solution were measured in order to correct the %biogenic opal values. 相似文献
6.
Akihiro Hachikubo Oleg Khlystov Masato Kida Hirotoshi Sakagami Hirotsugu Minami Satoshi Yamashita Nobuo Takahashi Hitoshi Shoji Gennadiy Kalmychkov Jeffrey Poort 《Geo-Marine Letters》2012,32(5-6):419-426
This study reports measurements of the Raman spectra of Lake Baikal gas hydrates and estimations of the hydration number of methane-rich samples. The hydration number of gas hydrates retrieved from the southern Baikal Basin (crystallographic structure I) was approx. 6.1. Consistent with previous results, the Raman spectra of gas hydrates retrieved from the Kukuy K-2 mud volcano in the central Baikal Basin indicated the existence of crystallographic structures I and II. Measurements of the dissociation heat of Lake Baikal gas hydrates by calorimetry (from the decomposition of gas hydrates to gas and water), employing the hydration number, revealed values of 53.7–55.5?kJ?mol–1 for the southern basin samples (structure I), and of 54.3–55.5?kJ?mol–1 for the structure I hydrates and 62.8–64.2?kJ?mol–1 for the structure II hydrates from the Kukuy K-2 mud volcano. 相似文献
7.
Shinya Magome Tomohiro Yamashita Takeshi Kohama Atsushi Kaneda Yuichi Hayami Satoru Takahashi Hidetaka Takeoka 《Journal of Oceanography》2007,63(5):761-773
Jellyfish patch formation is investigated by conducting a drifter experiment combined with aerial photography of a sustained
patch of the moon jellyfish in Hokezu Bay, Japan. Jellyfish patches are aggregations of individuals that are caused by a combination
of swimming (active influence) and advection by currents (passive influence). The drifter experiment involved the injection
of 49 drifters around a distinct surface patch of jellyfish within an area of approximately 300 m × 300 m. The drifters’ motion,
caused only by the passive influence, was recorded in a series of 38 aerial photographs taken over approximately 1 h. The
ambient uniform current field larger than the patch scale was estimated from the movement of the centroid position of drifters,
while the distribution of horizontal divergence and relative vorticity around the patch was estimated from the time-derivative
in areas of triangles formed by the drifters. The centroid positions of both drifters and patches moved stably toward the
bay head at different speeds. The difference vector between the patch and drifter centroids was directed to the sun, and was
opposite to the ambient current. The distributions of vorticity and divergence around patches exhibited inhomogeneity within
the patch scale, and the drifters in this nonuniform current field aggregated near the convergence area within 1 h. The results
suggest that horizontal patch formation is predominantly influenced by passive factors at the surface of Hokezu Bay. Furthermore,
the upward swimming against downwelling may make sustained patch in surface layer. 相似文献
8.
Seawater samples were collected in the North Pacific along 175°E during a cruise of the Northwest Pacific Carbon Cycle Study (NOPACCS) program in 1994. Many properties related to the carbonate system were analyzed. By using well-known ratios to correct for chemical changes in seawater, the CO2 concentration at a given depth was back calculated to its initial concentration at the time when the water left the surface in winter. We estimated sea-surface CO2 and titration alkalinity (TA) in present-day winter, from which we evaluated the degree of air-sea CO2 disequilibrium in winter was. Using a correction factor for air-sea CO2 disequilibrium in winter, we reconstructed sea-surface CO2 in pre-industrial times. The difference between the back-calculated initial CO2 and sea-surface CO2 in pre-industrial times should correspond to anthropgenic CO2 input. Although the mixing of different water masses may cause systematic error in the calculation, we found that the nonlinear effect induced by the mixing of different water masses was negligible in the upper layer of the North Pacific subtropical gyre along 175°E. The results of our improved method of assessing the distribution of anthropogenic CO2 in that region show marked differences from those obtained using the previous back-calculation method. 相似文献
9.
Shuichi Tanahashi Hiroshi Kawamura Toshihiko Matsuura Tomoyuki Takahashi Hiroyuki Yusa 《Journal of Oceanography》2000,56(3):345-358
We have developed an algorithm to estimate the wide-ranging Sea Surface Temperature (SST) data from the GMS-5 (Geostationary Meteorological Satellite) S-VISSR (Stretched-Visible Infrared Spin Scan Radiometer). Better SST estimates are realized by averaging the temporal variation of the VISSR calibration table and decreasing noise of the split-window terms using a spatial filter. The effects of the satellite zenith angle were examined in detail for better estimates, and VISSR-derived SSTs with root-mean-square (rms) error of 0.8 K were achieved using a new algorithm. The accuracy of SST estimates has been improved by using the temporal-spatial average of the split-window terms. Using the new techniques, we demonstrate that the hourly wide-ranging SST image data can be used to study the daily variations of SSTs in the Northern and Southern Pacific Oceans. 相似文献
10.
Strength and deformation behavior of the Shimanto accretionary complex across the Nobeoka thrust 下载免费PDF全文
A rapid reduction in sediment porosity from 60 to 70 % at seafloor to less than 10 % at several kilometers depth can play an important role in deformation and seismicity in the shallow portion of subduction zones. We conducted deformation experiments on rocks from an ancient accretionary complex, the Shimanto Belt, across the Nobeoka Thrust to understand the deformation behaviors of rocks along plate boundary faults at seismogenic depth. Our experimental results for phyllites in the hanging wall and shale‐tuff mélanges in the footwall of the Nobeoka Thrust indicate that the Shimanto Belt rocks fail brittlely accompanied by a stress drop at effective pressures < 80 MPa, whereas they exhibit strain hardening at higher effective pressures. The transition from brittle to ductile behavior in the shale–tuff mélanges lies on the same trend in effective stress–porosity space as that for clay‐rich and tuffaceous sediments subducting into the modern Nankai subduction zone. Both the absolute yield strength and the effective pressure at the brittle–ductile transition for the phyllosilicate‐rich materials are much lower than for sandstones. These results suggest that as the clay‐rich or tuffaceous sediments subduct and their porosities are reduced, their deformation behavior gradually transitions from ductile to brittle and their yield strength increases. Our results also suggest that samples of the ancient Shimanto accretionary prism can serve as an analog for underthrust rocks at seismogenic depth in the modern Nankai Trough. 相似文献