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1.
Rachelle B. Turnier Yaron Katzir Kouki Kitajima Ian J. Orland Michael J. Spicuzza John W. Valley 《Journal of Metamorphic Geology》2020,38(1):53-70
Corundum (Crn), including sapphire, occurs in emery pods surrounded by marble on the island of Naxos, Greece. The emery formed from bauxite deposited in karst that was metamorphosed to 400–700°C at 20–15 Ma. Many of these rocks initially appeared well suited for refractory accessory mineral (RAM) thermometry, which uses oxygen isotope fractionation between a RAM – corundum – and a modally dominant phase with faster diffusion of oxygen – calcite (Cc) – to determine peak metamorphic temperatures. However, previous attempts at oxygen isotope thermometry were confounded by highly variable fractionations (Δ18O) measured at mm-scale and the uncertain calibration of Δ18O(Cc-Crn) versus temperature. Secondary ion mass spectrometry (SIMS) permits in situ analysis of δ18O in corundum and calcite at the 10-μm scale in adjacent grains where textures suggest peak metamorphic equilibrium was attained. SIMS analyses of adjacent mineral pairs in eight rocks yield values of Δ(Cc-Crn) that systematically decrease from 7.2 to 2.9‰ at higher metamorphic grade. Pairing these data with independent temperature estimates from mineral isograds yields an empirical calibration of 1,000 lnα(Cc-Crn) = 2.72 ± 0.3 × 106/T2 (T in K). The new fractionations (2.7‰ at 1,000 K) are significantly smaller than those calculated from the modified increment method (6.5‰ at 1,000 K; Zheng, Geochimica et Cosmochimica Acta, 1991, 55:2299–2307; Zheng, Mineral Mag, 1994, 58A:1000–1001), which yield unreasonably high temperatures of 630 to 1,140°C when applied to the new Naxos data. The new calibration of Δ(Cc-Crn) can be combined with published fractionations to calculate A-factors for corundum versus a range of 14 other minerals. These new fractionation factors can be used for thermometry or to constrain the genesis of corundum. A compilation of gem corundum δ18O values shows that many igneous sapphires, including important deposits of basalt-associated sapphire, are mildly elevated in δ18O relative to the calculated range in equilibrium with mantle values (4.4–5.7‰) and formed from evolved magmas. 相似文献
2.
Akizumi Ishida Kouki Kitajima Ko Hashizume Michael J. Spicuzza Alexander Zaitsev Daniel J. Schulze John W. Valley 《Geostandards and Geoanalytical Research》2023,47(3):569-578
Simultaneous analysis of carbon and nitrogen isotope ratios by SIMS was applied for the first-time to a natural diamond from the Kelsey Lake kimberlite, State Line Distinct, Colorado (UWD-1). This in situ procedure is faster, reduces sample size for analysis, and measures both isotope ratios from a single ~ 10 μm diameter pit, a critical advantage for zoned diamonds. The carbon isotope ratio (expressed as δ13CVPDB) of the bulk UWD-1 crystal, determined by the conventional combustion method in the present study, is -5.9‰ ± 0.2‰ (VPDB, 2s). Nitrogen mass fraction ([N]) and isotope ratio (expressed as δ15NAir) were determined by stepwise combustion and gas-source mass-spectrometry, resulting in 553 ± 64 μg g-1 and -6.7‰ ± 1.1‰ (Air, 2s), respectively. Secondary ions of 12C2-, 12C13C-, 12C14N-, and 12C15N- were simultaneously measured by SIMS using three Faraday cups and one electron multiplier. The spot-to-spot reproducibility of δ13C and δ15N values for the UWD-1 (178 spots on sixteen chips, 10 μm spots), were 0.3‰ and 1.6‰, respectively (2s). While 12C14N-/12C2- ratios, which are an indicator for [N], varied up to 12% among these sixteen chips, such variation did not correlate with either δ13C or δ15N values. We propose that UWD-1 is a suitable reference sample for microscale in situ analysis of δ13C and δ15N values in diamond samples. 相似文献
3.
Fluid generation and evolution during exhumation of deeply subducted UHP continental crust: Petrogenesis of composite granite–quartz veins in the Sulu belt,China 
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下载免费PDF全文 S.‐J. Wang L. Wang M. Brown P. M. Piccoli T. E. Johnson P. Feng H. Deng K. Kitajima Y. Huang 《Journal of Metamorphic Geology》2017,35(6):601-629
Composite granite–quartz veins occur in retrogressed ultrahigh pressure (UHP) eclogite enclosed in gneiss at General's Hill in the central Sulu belt, eastern China. The granite in the veins has a high‐pressure (HP) mineral assemblage of dominantly quartz+phengite+allanite/epidote+garnet that yields pressures of 2.5–2.1 GPa (Si‐in‐phengite barometry) and temperatures of 850–780°C (Ti‐in‐zircon thermometry) at 2.5 GPa (~20°C lower at 2.1 GPa). Zircon overgrowths on inherited cores and new grains of zircon from both components of the composite veins crystallized at c. 221 Ma. This age overlaps the timing of HP retrograde recrystallization dated at 225–215 Ma from multiple localities in the Sulu belt, consistent with the HP conditions retrieved from the granite. The εHf(t) values of new zircon from both components of the composite veins and the Sr–Nd isotope compositions of the granite consistently lie between values for gneiss and eclogite, whereas δ18O values of new zircon are similar in the veins and the crustal rocks. These data are consistent with zircon growth from a blended fluid generated internally within the gneiss and the eclogite, without any ingress of fluid from an external source. However, at the peak metamorphic pressure, which could have reached 7 GPa, the rocks were likely fluid absent. During initial exhumation under UHP conditions, exsolution of H2O from nominally anhydrous minerals generated a grain boundary supercritical fluid in both gneiss and eclogite. As exhumation progressed, the volume of fluid increased allowing it to migrate by diffusing porous flow from grain boundaries into channels and drain from the dominant gneiss through the subordinate eclogite. This produced a blended fluid intermediate in its isotope composition between the two end‐members, as recorded by the composite veins. During exhumation from UHP (coesite) eclogite to HP (quartz) eclogite facies conditions, the supercritical fluid evolved by dissolution of the silicate mineral matrix, becoming increasingly solute‐rich, more ‘granitic’ and more viscous until it became trapped. As crystallization began by diffusive loss of H2O to the host eclogite concomitant with ongoing exhumation of the crust, the trapped supercritical fluid intersected the solvus for the granite–H2O system, allowing phase separation and formation of the composite granite–quartz veins. Subsequently, during the transition from HP eclogite to amphibolite facies conditions, minor phengite breakdown melting is recorded in both the granite and the gneiss by K‐feldspar+plagioclase+biotite aggregates located around phengite and by K‐feldspar veinlets along grain boundaries. Phase equilibria modelling of the granite indicates that this late‐stage melting records P–T conditions towards the end of the exhumation, with the subsolidus assemblage yielding 0.7–1.1 GPa at <670°C. Thus, the composite granite–quartz veins represent a rare example of a natural system recording how the fluid phase evolved during exhumation of continental crust. The successive availability of different fluid phases attending retrograde metamorphism from UHP eclogite to amphibolite facies conditions will affect the transport of trace elements through the continental crust and the role of these fluids as metasomatic agents interacting with the mantle wedge in the subduction channel. 相似文献
4.
Fumio Kitajima Tomoki NakamuraNobuo Takaoka Tatsushi Murae 《Geochimica et cosmochimica acta》2002,66(1):163-172
The degrees of thermal metamorphism of 10 CM chondrites and of the Allende CV3 chondrite were evaluated from the viewpoint of “graphitization” of the carbonaceous macromolecular matter by means of flash pyrolysis-gas chromatography (GC). The unheated chondrites, Yamato- (Y-) 791198, Murray and Cold Bokkeveld, yielded larger amounts and wider varieties of pyrolyzates than the chondrites strongly heated in the parent asteroids, Y-82054, Y-86695, and Belgica- (B-) 7904, and Asuka- (A-) 881334 (more strongly heated than Y-793321, which has been weakly heated, but lesser than the other strongly heated meteorites). The weakly heated chondrites, Y-793321 and A-881458, showed intermediate features. The data indicate that graphitization of the carbonaceous matter is most extreme in the strongly heated chondrites and that during graphitization, the matter has lost its labile portion, which can generate pyrolyzates such as naphthalene. In order to establish a new method for the evaluation of the degree of graphitization of chondritic carbonaceous matter, a diagram was developed to show the relationship between the total amounts of pyrolyzates with retention times later than 5 min (=SRT>5) and the ratio of the amount of naphthalene, a pyrolysis product, to SRT>5 (=SN/SRT>5). The diagram indicates a possible evolutionary pathway of graphitization of the carbonaceous matter in carbonaceous chondrites. 相似文献
5.
Ahmad Ismail Syaizwan Zahmir Zulkifli Ferdius Mohamat Yusuff Usuki Yasuteru Kitajima Sachiko Arizono Koji 《湿地科学》2007,5(4):322-325
This study was conducted to assess the existing concentration of 17β-estradiol(E2)in the surface water samples collected from rivers and lakes around Klang Valley,Malaysia.E2,which is a natural feminizing chemical produced in female organisms,regularly used to compare with other environmental estrogens because they behave similarly and react effectively as a hormone at a very low concentration.It was found that the average concentration of E2 in the aquatic environment of Klang Valley was(14.08 ±3.67)pg/mL,which was 14 times higher than those in the Japanese aquatic environment in this study.The river system had the average concentration of(20.02±5.26)pg/mL while the lake had an average concentration of(5.91±3.39)pg/mL.The E2 concentration was presumed high if the sources occurred nearby the area.Current levels of E2 in the aquatic environment may possess threats to existing aquatic organisms.Since high level of E2 has been discovered in the aquatic environment around Klang Valley,further studies and monitoring of E2 and other EDCs concentrations are needed to determine their levels in Malaysian aquatic environment and help to control these chemicals pollution in the aquatic environment. 相似文献
6.
Strength and deformation behavior of the Shimanto accretionary complex across the Nobeoka thrust 下载免费PDF全文
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
7.
Secondary Ion Mass Spectrometry Bias on Isotope Ratios in Dolomite–Ankerite,Part II: δ13C Matrix Effects 下载免费PDF全文
下载免费PDF全文 Maciej G. Śliwiński Kouki Kitajima Reinhard Kozdon Michael J. Spicuzza John H. Fournelle Adam Denny John W. Valley 《Geostandards and Geoanalytical Research》2016,40(2):173-184
This study is Part II of a series that documents the development of a suite of calibration reference materials for in situ SIMS analysis of stable isotope ratios in Ca‐Mg‐Fe carbonates. Part I explored the effects of Fe2+ substitution on SIMS δ18O bias measured from the dolomite–ankerite solid solution series [CaMg(CO3)2–CaFe(CO3)2], whereas this complementary work explores the compositional dependence of SIMS δ13C bias (calibrated range: Fe# = 0.004–0.789, where Fe# = molar Fe/(Mg+Fe)). Under routine operating conditions for carbonate δ13C analysis at WiscSIMS (CAMECA IMS 1280), the magnitude of instrumental bias increased exponentially by 2.5–5.5‰ (session‐specific) with increasing Fe‐content in the dolomite structure, but appeared insensitive to minor Mn substitution [< 2.6 mole % Mn/(Ca+Mg+Fe+Mn)]. The compositional dependence of bias (i.e., the matrix effect) was expressed using the Hill equation, yielding calibration residual values ≤ 0.3‰ relative to CRM NBS‐19 for eleven carbonate reference materials (6‐μm‐diameter spot size measurements). Based on the spot‐to‐spot repeatability of a drift monitor material that ‘bracketed’ each set of ten sample‐spot analyses, the analytical precision was ± 0.6–1.2‰ (2s, standard deviations). The analytical uncertainty for individual sample analyses was approximated by combining the precision and calibration residual values (propagated in quadrature), suggesting an uncertainty of ± 1.0–1.5‰ (2s). 相似文献
8.
Masayuki Uesugi Ryo Noguchi Tooru Matsumoto Junya Matsuno Takashi Nagano Akira Tsuchiyama Shigenori Harada Kaori Yokoyama Yoshiaki Yodo Noboru Takeda Toru Yada Shogo Yakame Yuzuru Karouji Yukihiro Ishibashi Masanao Abe Tatsuaki Okada Akio Fujimura Mitsuru Ebihara Fumio Kitajima Keisuke Nagao Tomoki Nakamura Hiroshi Naraoka Takaaki Noguchi Ryuji Okazaki Hisayoshi Yurimoto 《Meteoritics & planetary science》2014,49(7):1186-1201
We report the investigation of cutting methods for Hayabusa samples. The purpose of our study is to explore the possibility of applying multiple analyses to a single particle effectively. We investigated the cutting performance of a blade dicing saw, laser, focused ion beam (FIB), and physical breaking by microindenter. Cutting performance was examined by estimating the aspect ratio of the cut slit, i.e., depth over width of the slit. We also investigated the possible contamination and sample damage by cutting. The result of the investigation shows that we can cut the samples from <50 μm to 500 μm using those methods with aspect ratios from 10 to 20, although they would introduce some contamination or damage to the samples. Our investigations also provide an important basis for the analysis of samples obtained by future sample return missions. 相似文献
9.
Ashley K. Russell Kouki Kitajima Ariel Strickland L. Gordon Medaris Jr. Daniel J. Schulze John W. Valley 《Contributions to Mineralogy and Petrology》2013,165(1):103-116
In situ analysis reveals that eclogite-facies garnets are zoned in δ18O with lower values in the core and rims that are ~1.5 to 2.5 ‰ higher. This pattern is present in 9 out of 12 garnets analyzed by SIMS from four orogenic eclogite terranes, and correlates with an increase in the mole fraction of pyrope and Mg/Fe ratio from core to rim, indicating prograde garnet growth. At the maximum temperatures and the time-scales experienced by these garnets, calculated intragranular diffusion distances for oxygen are small (<5 μm), indicating that δ18O records primary growth zoning and not diffusive exchange. The oxygen isotope gradients are larger than could form due to temperature changes during closed-system mineral growth. Thus, gradients reflect the compositions of fluids infiltrating during prograde metamorphism. Values of δ18O in garnet cores range from ?1 to 15 ‰, likely preserving the composition of the eclogite protoliths. Two garnet cores from the Almenningen eclogite in the Western Gneiss Region, Norway, have δ18O ~?1 ‰ and are the first negative δ18O eclogites identified in the region. In contrast with orogenic eclogites, seven high δ18O garnets (>5 ‰) from two kimberlites are homogeneous in δ18O, possibly due to diffusive exchange, which is possible for prolonged periods at higher mantle temperatures. Homogeneity of δ18O in garnets outside the normal mantle range (5–6 ‰) may be common in kimberlitic samples. 相似文献
10.
Tsutomu Ota Atsushi Utsunomiya Yuko Uchio Yukio Isozaki Mikhail M. Buslov Akira Ishikawa Shigenori Maruyama Koki Kitajima Yoshiyuki Kaneko Hiroshi Yamamoto Ikuo Katayama 《Journal of Asian Earth Sciences》2007,30(5-6):666-695
The Gorny Altai region in southern Siberia is one of the key areas in reconstructing the tectonic evolution of the western segment of the Central Asian Orogenic Belt (CAOB). This region features various orogenic elements of Late Neoproterozoic–Early Paleozoic age, such as an accretionary complex (AC), high-P/T metamorphic (HP) rocks, and ophiolite (OP), all formed by ancient subduction–accretion processes. This study investigated the detailed geology of the Upper Neoproterozoic to Lower Paleozoic rocks in a traverse between Gorno-Altaisk city and Lake Teletskoy in the northern part of the region, and in the Kurai to Chagan-Uzun area in the southern part. The tectonic units of the studied areas consist of (1) the Ediacaran (=Vendian)–Early Cambrian AC, (2) ca. 630 Ma HP complex, (3) the Ediacaran–Early Cambrian OP complex, (4) the Cryogenian–Cambrian island arc complex, and (5) the Middle Paleozoic fore-arc sedimentary rocks. The AC consists mostly of paleo-atoll limestone and underlying oceanic island basalt with minor amount of chert and serpentinite. The basaltic lavas show petrochemistry similar to modern oceanic plateau basalt. The 630 Ma HP complex records a maximum peak metamorphism at 660 °C and 2.0 GPa that corresponds to 60 km-deep burial in a subduction zone, and exhumation at ca. 570 Ma. The Cryogenian island arc complex includes boninitic rocks that suggest an incipient stage of arc development. The Upper Neoproterozoic–Lower Paleozoic complexes in the Gorno-Altaisk city to Lake Teletskoy and the Kurai to Chagan-Uzun areas are totally involved in a subhorizontal piled-nappe structure, and overprinted by Late Paleozoic strike-slip faulting. The HP complex occurs as a nappe tectonically sandwiched between the non- to weakly metamorphosed AC and the OP complex. These lithologic assemblages and geologic structure newly documented in the Gorny Altai region are essentially similar to those of the circum-Pacific (Miyashiro-type) orogenic belts, such as the Japan Islands in East Asia and the Cordillera in western North America. The Cryogenian boninite-bearing arc volcanism indicates that the initial stage of arc development occurred in a transient setting from a transform zone to an incipient subduction zone. The less abundant of terrigenous clastics from mature continental crust and thick deep-sea chert in the Ediacaran–Early Cambrian AC may suggest that the southern Gorny Altai region evolved in an intra-oceanic arc-trench setting like the modern Mariana arc, rather than along the continental arc of a major continental margin. Based on geological, petrochemical, and geochronological data, we synthesize the Late Neoproterozoic to Early Paleozoic tectonic history of the Gorny Altai region in the western CAOB. 相似文献