Hf-Nd isotope evidence for contemporaneous subduction processes in the source of late Archean arc lavas from the Superior Province, Canada   总被引：2，自引：0，他引：2  

Ali Polat  Carsten Münker 《Chemical Geology》2004,213(4):403-429

Volcanic suites from Wawa greenstone belts in the southern Superior Province comprise an association of typical late Archean arc volcanic rocks including adakites, magnesian andesites (MA), niobium-enriched basalts (NEB), and ‘normal’ tholeiitic to calc-alkaline basalts to rhyolites. The adakites represent melts from subducted oceanic crust and all other suites were derived from the mantle wedge above the subducting oceanic lithosphere. The magnesian andesites are interpreted to be the product of hybridization of adakite melts with arc mantle wedge peridotite. The initial ?_Hf values of the ∼2.7 Ga Wawa adakites (+3.5 to +5.2), magnesian andesites (+2.6 to +5.1), niobium-enriched basalts (+4.4 to +6.6), and ‘normal’ tholeiitic to calc-alkaline arc basalts (+5.3 to +6.4) are consistent with long-term depleted mantle sources. The niobium-enriched basalts and ‘normal’ arc basalts have more depleted ?_Hf values than the adakites and magnesian andesites. The initial ?_Nd values in the magnesian andesites (+0.4 to +2.0), niobium-enriched basalts (+1.4 to +2.4), and ‘normal’ arc tholeiitic to calc-alkaline basalts (+1.6 to +2.9) overlap with, but extend to lower values than, the slab-derived adakites (+2.3 to +2.8). The lower initial ?_Nd values in the mantle-wedge-derived suites, particularly in the magnesian andesites, are attributed to recycling of an Nd-enriched component with lower ?_Nd to the mantle wedge. As a group, the slab-derived adakites plot closest to the 2.7 Ga depleted mantle value in ?_Nd versus ?_Hf space, additionally suggesting that the Nd-enriched component in the mantle wedge did not originate from the 2.7 Ga slab-derived melts. Accordingly, we suggest that the enriched component had been added to the mantle wedge at variable proportions by recycling of older continental material. This recycling process may have occurred as early as 50-70 Ma before the initiation of the 2.7 Ga subduction zone. The selective enrichment of Nd in the sources of the Superior Province magmas can be explained by experimental studies and geochemical observations in modern subduction systems, indicating that light rare earth elements (e.g., La, Ce, Sm, Nd) are more soluble than high field strength elements (e.g., Zr, Hf, Nb, Ta) in aqueous fluids that are derived from subducted slabs. As a corollary, we suggest that the recycled Nd-enriched component was added to the mantle source of the Wawa arc magmas by dehydration of subducted sediments.  相似文献   

Iron isotope fractionation during planetary differentiation   总被引：4，自引：0，他引：4  

Stefan Weyer  Ariel D. Anbar  Carsten Münker  Alan B. Woodland 《Earth and Planetary Science Letters》2005,240(2):251-264

The Fe isotope composition of samples from the Moon, Mars (SNC meteorites), HED parent body (eucrites), pallasites (metal and silicate) and the Earth's mantle were measured using high mass resolution MC-ICP-MS. These high precision measurements (δ⁵⁶Fe ≈ ± 0.04‰, 2 S.D.) place tight constraints on Fe isotope fractionation during planetary differentiation.Fractionation during planetary core formation is confined to < 0.1‰ for δ⁵⁶Fe by the indistinguishable Fe isotope composition of pallasite bulk metal (including sulfides and phosphides) and olivine separates. However, large isotopic variations (≈ 0.5‰) were observed among pallasite metal separates, varying systematically with the amounts of troilite, schreibersite, kamacite and taenite. Troilite generally has the lightest (δ⁵⁶Fe ≈ − 0.25‰) and schreibersite the heaviest (δ⁵⁶Fe ≈ + 0.2‰) Fe isotope composition. Taenite is heavier then kamacite. Therefore, these variations probably reflect Fe isotope fractionation during the late stage evolution and differentiation of the S- and P-rich metal melts, and during low-temperature kamacite exsolution, rather than fractionation during silicate-metal separation.Differentiation of the silicate portion of planets also seems to fractionate Fe isotopes. Notably, magmatic rocks (partial melts) are systematically isotopically heavier than their mantle protoliths. This is indicated by the mean of 11 terrestrial peridotite samples from different tectonic settings (δ⁵⁶Fe = + 0.015 ± 0.018‰), which is significantly lighter than the mean of terrestrial basalts (δ⁵⁶Fe = + 0.076 ± 0.029‰). We consider the peridotite mean to be the best estimate for the Fe isotope composition of the bulk silicate Earth, and probably also of bulk Earth. The terrestrial basaltic mean is in good agreement with the mean of the lunar samples (δ⁵⁶Fe = + 0.073 ± 0.019‰), excluding the high-Ti basalts. The high-Ti basalts display the heaviest Fe isotope composition of all rocks measured here (δ⁵⁶Fe ≈ + 0.2‰). This is interpreted as a fingerprint of the lunar magma ocean, which produced a very heterogeneous mantle, including the ilmenite-rich source regions of these basalts.Within uncertainties, samples from Mars (SNC meteorites), HED (eucrites) and the pallasites (average olivine + metal) have the same Fe isotope compositions as the Earth's mantle. This indicates that the solar system is very homogeneous in Fe isotopes. Its average δ⁵⁶Fe is very close to that of the IRMM-014 standard.  相似文献   

Late Cretaceous eclogite in the Eastern Rhodopes (Bulgaria): evidence for subduction under the Sredna Gora magmatic arc     

Miladinova  Irena  Froitzheim  Nikolaus  Nagel  Thorsten J.  Janák  Marian  Georgiev  Neven  Fonseca  Raúl O. C.  Sandmann  Sascha  Münker  Carsten 《International Journal of Earth Sciences》2018,107(6):2083-2099

International Journal of Earth Sciences - The Rhodopes in Bulgaria and Greece represent a nappe stack of high-grade units with polymetamorphic history. Constraining the time of metamorphism in...  相似文献   

Dating the initiation of Piemonte-Liguria Ocean subduction: Lu–Hf garnet chronometry of eclogites from the Theodul Glacier Unit (Zermatt-Saas zone,Switzerland)     

Sebastian Weber  Sascha Sandmann  Irena Miladinova  Raúl O. C. Fonseca  Nikolaus Froitzheim  Carsten Münker  Kurt Bucher 《Swiss Journal of Geoscience》2015,108(2-3):183-199

  相似文献   

Geochemical constraints on the petrogenesis of arc picrites and basalts,New Georgia Group,Solomon Islands   总被引：2，自引：0，他引：2  

Stephan?SchuthEmail author  Arno?Rohrbach  Carsten?Münker  Chris?Ballhaus  Dieter?Garbe-Sch?nberg  Cromwell?Qopoto 《Contributions to Mineralogy and Petrology》2004,148(3):288-304

Island arc picrites are restricted to a few localities including the Lesser Antilles, Japan, Vanuatu and the Solomon Islands. The picrite occurrences appear to be linked to the subduction of young, hot oceanic crust and anomalous geotherms. At the Solomon arc, the Australian plate is presently subducted beneath the Pacific plate. A particular feature of the Solomon arc is the subduction of a spreading center (Woodlark Ridge). In the Solomon Islands, picrites only occur in the New Georgia archipelago, located above or close to the subducting Woodlark Ridge. These picrites contain between 12 and 30 wt% MgO, the associated primitive basalts show MgO contents from 11.5 to 13.6 wt%. Linear trends defined by Cr, Ni and other trace elements vs. MgO indicate that the picritic bulk compositions originate from mixing between a basaltic-picritic melt and a Mg- and Cr-rich endmember, rather than from fractional crystallization of extremely Mg-rich magmas. Major and trace element modeling identify mantle wedge peridotite as the most likely mixing endmember. Trace element abundances in the Solomon arc picrites indicate a mantle source enrichment by subduction components and a large depletion of Nb and Ta that is typical for island arc volcanic rocks. Most incompatible trace element patterns of the New Georgia picrites and basalts are parallel, supporting a cogenetic evolution of these rocks by mixing processes. ⁸⁷Sr/⁸⁶Sr and Nd values in the basalts and picrites range from 0.7033 to 0.7043 and +5.8 to +8.0, respectively. These values partially overlap with compositions of the Indian MORB field. Alternatively, subducted sediment and fluids from altered MORB may have displaced the Sr isotope composition to more radiogenic ⁸⁷Sr/⁸⁶Sr. Hf values range from +12.2 to +14.6 and show in combination with Nd that the picrites were most likely generated within the Indian mantle domain.This revised version was published online September 2004 with a correction to Table 2.  相似文献   

末次间冰期大西洋中层水突然变暖对温盐环流减缓的响应     

张光威 《海洋地质前沿》2003,19(11):15-16

气候模拟研究预示 ,虽然全球气候仍在变暖以及水动力循环也在加强 ,但人类活动引起的温室气体浓度的增加 ,可导致大西洋经向倒转环流 (温盐环流 ,THC)的减弱甚至关闭(Cubasch等 ,2 0 0 1 )。因此 ,这是控制大西洋温盐环流得以持续的根本所在。但是 ,现今THC的实际观测还不足以说明其环流的强度是在变化的。气候模型显示 ,THC减缓的结果导致赤道大西洋中层水的显著且快速增温 ,表明大西洋中等深度的水体温度变化可作为THC的示踪剂。对大洋循环模型采用不同的边界条件 ,选择现今和冰川气候条件来演示大西洋中层水是如何响应的。中层水的…  相似文献   

Analysis of the IR and sub-MM emission of four post-AGB stars     

Carsten Kömpe  Joachim Gürtler  Thomas Henning 《Astrophysics and Space Science》1995,224(1-2):353-356

The goal of this work is to derive the physical properties of dust envelopes around post-AGB stars by means of radiative transfer calculations. The model spectral energy distributions (SEDs) have been compared with observational data of the post-AGB stars IRAS 10215-5916, 16342-3814, 17150-3224, and 19500-1709 in the wavelength range from 0.4 to 1300µm. The match between our model SEDs and the observational data is very satisfactory. As a result, we have obtained estimates of the inner and outer radii, the density, the temperature, and the mass of the envelopes of the four objects.  相似文献   

Bottom-current control on sedimentation in the western Bellingshausen Sea, West Antarctica   总被引：1，自引：0，他引：1  

Carsten Scheuer  Karsten Gohl  Gleb Udintsev 《Geo-Marine Letters》2006,26(2):90-101

A set of single- and multi-channel seismic reflection profiles provide insights into the younger Cenozoic sedimentation history of the continental rise in the western Bellingshausen Sea, west and north of Peter I Island. This area has been strongly influenced by glacially controlled sediment supply from the continental shelf, interacting with a westward-flowing bottom current. From south to north, the seismic data show changes in the symmetry and structure of a prominent sediment depocentre. Its southernmost sector provides evidence of sediment drift whereas northwards the data show a large channel-levee complex, with a western levee oriented in the opposite direction to that of the drift in the south. This pattern indicates the northward-decreasing influence of a westward-flowing bottom contour current in the study area. Topographic data suggest the morphologic ridges at Peter I Island to be the main features responsible for variable bottom-current influence, these acting as barrier to the bottom current and entrained sedimentary material. West of Peter I Island, the east-orientated Coriolis force remains effective in deflecting the suspended load of the turbidity currents towards the west, thereby promoting growth of the western channel levee. Calculated sediment accumulation rates based on seismic data reveal Depocentre C to consist of younger Cenozoic material supplied by glacial transport and modified by contour currents in the western Bellingshausen Sea. These findings demonstrate that the shape, structure and distribution of sediment mounds and estimates of sediment accumulation rates can be associated to the influence of bottom currents and their long-term evolution in response to tectonic movements, ice-sheet dynamics and deep-water formation.  相似文献   

Estimation of kinetic Monod parameters for anaerobic degradation of benzene in groundwater   总被引：1，自引：0，他引：1  

Stefan Gödeke  Carsten Vogt  Mario Schirmer 《Environmental Geology》2008,55(2):423-431

To date, evidence for the degradation of benzene under anaerobic conditions has been established only in few studies under field and laboratory conditions. Recently, we demonstrated the mineralization of benzene under sulfate-reducing conditions in a large-scale column experiment at a field site by balancing electrons (Vogt et al. in Biodegradation, 2007, in press). Here, from a modelling approach, kinetic Monod parameters are estimated for the degradation of benzene in the columns, Monod kinetics proved useful to simulate benzene concentrations at the column outflow. The uncertainty of the obtained parameters is determined in a sensitivity analysis. A total mass of degraded benzene of 23 g or 80% of the total influx over a period of three months was calculated. The estimated maximum utilization rate was calculated to be around 70 times lower than from aerobic benzene degradation experiments.  相似文献   

The Far‐Infrared Emission of Galaxies     

Carsten Kramer  Albrecht Poglitsch  Jürgen Stutzki  Andreas Eckart 《Astronomische Nachrichten》2005,326(7):523-534

C01 Study of local infrared bright galaxies with HERSHCEL‐PACS C02 PDR modeling of the COBE Far‐Infrared data of the Milky Way C03 MAMBO observations of BzK‐selected vigorous starburst galaxies at z ∼ 2 C04 Starburst galaxies in the far‐infrared. Modelling the line, PAH and dust continuum emission C05 The SED from isothermal clouds C06 PDRs in M83 and M51: The road to HIFI/Herschel and SOFIA C07 Large Scale Mapping of Molecular Gas in the Vicinity of 30 Doradus in the Large Magellanic Cloud C08 Modelling far‐infrared emission from dust in gas‐rich galaxies C09 [CII]/CO(1‐0) Line Ratio at low Metallicities C10 Gas, Stars and Dust in the Spiral Arms of M51 C11 The ISOPHOT 170 micron Serendipity Survey (ISOSS) catalog of optically identified galaxies C12 Spitzer Images of M33: A Probe to Radio‐FIR Correlation C13 Observations of far‐infrared emission from dust in gas‐rich galaxies C14 Dust and Gas in Nearby Galaxies: First Results from SINGS and THINGS C15 Sequential Starburst in Arp220?  相似文献