Mapping lithospheric boundaries using Os isotopes of mantle xenoliths: An example from the North China Craton   总被引：5，自引：0，他引：5  

Jingao Liu  Roberta L. Rudnick  Shan Gao  Philip M. Piccoli  Wen-liang Xu 《Geochimica et cosmochimica acta》2011,75(13):3881-6182

The petrology, mineral compositions, whole rock major/trace element concentrations, including highly siderophile elements, and Re-Os isotopes of 99 peridotite xenoliths from the central North China Craton were determined in order to constrain the structure and evolution of the deep lithosphere. Samples from seven Early Cretaceous-Tertiary volcanic centers display distinct geochemical characteristics from north to south. Peridotites from the northern section are generally more fertile (e.g., Al₂O₃ = 0.9-4.0%) than those from the south (e.g., Al₂O₃ = 0.2-2.2%), and have maximum whole-rock Re-depletion Os model ages (T_RD) of ∼1.8 Ga suggesting their coeval formation in the latest Paleoproterozoic. By contrast, peridotites from the south have maximum T_RD model ages that span the Archean-Proterozoic boundary (2.1-2.5 Ga). Peridotites with model ages from both groups are found at Fansi, the southernmost locality in the northern group, which likely marks a lithospheric boundary. The Neoarchean age of the lithospheric mantle in the southern section matches that of the overlying crust and likely reflects the time of amalgamation of the North China Craton via collision between the Eastern and Western blocks. The Late Paleoproterozoic (∼1.8 Ga) lithospheric mantle beneath the northern section is significantly younger than the overlying Archean crust, indicating that the original lithospheric mantle was replaced in this region, either during a major north-south continent-continent collision that occurred during assembly of the Columbia supercontinent at ∼1.8-1.9 Ga, or from extrusion of ∼1.9 Ga lithosphere from the Khondalite Belt beneath the northern Trans-North China Orogen, during the ∼1.85 Ga continental collision between Eastern and Western blocks. Post-Cretaceous heating of the southern section is indicated by high temperatures (>1000 °C) recorded in peridotites from the 4 Ma Hebi suite, which are significantly higher than the temperatures recorded in peridotites from the nearby Early Cretaceous Fushan suite (<720 °C), and likely reflects significant lithospheric thinning after the Early Cretaceous. Combining previous Os isotope results on mantle xenoliths from the eastern North China Craton with our new data, it appears that lithospheric thinning and replacement may have evolved from east to west with time, commencing before the Triassic on the eastern edge of the craton, occurring during the Jurassic-Cretaceous within the interior, and post-dating 125 Ma on the westernmost boundary.  相似文献   

The sagging deep-seated gravitational movements on the eastern side of Mt. Amiata (Tuscany,Italy)     

Mauro Coltorti  Andrea Brogi  Lorenzo Fabbrini  Dario Firuzabadì  Lapo Pieranni 《Natural Hazards》2011,59(1):191-208

The eastern side of the Mt. Amiata volcano is affected by a series of deep-seated gravitational slope deformations (DsGSDs). The San Piero and the Podere Mezzavia DsGSDs affect the lower part of the slope. The main escarpments are located on the outer edges of the lava flows, but the landslides mostly affect the pre-volcanic Ligurian Terrains. A deeper movement, possibly exceeding 100 m in thickness, is evidenced by a long trench at the base of the main escarpment that indicates a sagging type movement. This deeper movement is responsible for the activation of a series of superficial rock and mud flows that show evidence of ongoing activity. The most likely location of the sliding surface is the tectonized contact between the Santa Fiora and Argille a Palombini Fms within the Ligurian units, although the superficial landslides prevent our determining with certainty if a clear-cut sliding surface already developed connecting the upper and the lower parts of the slope. These DsGSDs were activated along the flanks of a larger movement that affects the lava flow units cropping out in the middle slope of the volcano. A long main escarpment, secondary escarpments, trenches and borehole data suggest that the thickness could locally exceed 200 m and generate another sagging type movement. Up-slope and up-movement-facing counterscarps indicate the existence of a listric elongated spoon-shaped compound embryonic sliding surface. This sagging, which hosts the towns of Abbadia San Salvatore and Piancastagnaio, appears to be in a quiescent stage, according to preliminary monitoring with a global positioning system (GPS) network. The downcutting of the river network along the softer Pliocene terrains of the Radicofani basin is enhanced by the general uplift of the Apennines and seems to be the major factor in the activation of these DsGSDs.  相似文献   

GSD‐1G and MPI‐DING Reference Glasses for In Situ and Bulk Isotopic Determination     

Klaus Peter Jochum  Steven A. Wilson  Wafa Abouchami  Marghaleray Amini  Jérome Chmeleff  Anton Eisenhauer  Ernst Hegner  Linda M. Iaccheri  Bruno Kieffer  Joachim Krause  William F. McDonough  Regina Mertz‐Kraus  Ingrid Raczek  Roberta L. Rudnick  Denis Scholz  Grit Steinhoefel  Brigitte Stoll  Andreas Stracke  Sonia Tonarini  Dominique Weis  Ulrike Weis  Jon D. Woodhead 《Geostandards and Geoanalytical Research》2011,35(2):193-226

This paper contains the results of an extensive isotopic study of United States Geological Survey GSD‐1G and MPI‐DING reference glasses. Thirteen different laboratories were involved using high‐precision bulk (TIMS, MC‐ICP‐MS) and microanalytical (LA‐MC‐ICP‐MS, LA‐ICP‐MS) techniques. Detailed studies were performed to demonstrate the large‐scale and small‐scale homogeneity of the reference glasses. Together with previously published isotopic data from ten other laboratories, preliminary reference and information values as well as their uncertainties at the 95% confidence level were determined for H, O, Li, B, Si, Ca, Sr, Nd, Hf, Pb, Th and U isotopes using the recommendations of the International Association of Geoanalysts for certification of reference materials. Our results indicate that GSD‐1G and the MPI‐DING glasses are suitable reference materials for microanalytical and bulk analytical purposes.  相似文献   

Preliminary Results on the Solar Photospheric Dynamics Observed with Vamos     

Oliviero  M.  Moretti  P.F.  Severino  G.  Straus  Th.  Magrì  M.  Tripicchio  A. 《Solar physics》2002,209(1):21-35

The intensity and velocity fluctuations, observed simultaneously, are a powerful diagnostic tool of the dynamics of the solar atmosphere. The phase relation between the fluctuations can improve our knowledge of the solar background, its relation with the acoustic sources, and its interaction with the solar acoustic oscillations. Furthermore, the opposite asymmetries observed along the p-mode line profiles in the intensity and velocity power spectra contain information about the source of the solar acoustic oscillations. For these reasons, it is relevant to study the height dependence of the asymmetries and phases in the solar atmosphere. In this paper, we present the results from the analysis of observations performed by the VAMOS instrument in the potassium 769.9 nm line and Na i D lines, and compare the measured phases with those obtained at different layers in the solar atmosphere by different instruments, spanning from the base of the photosphere to the low chromosphere.  相似文献   

Technical guidelines for the assessment of earthquake induced liquefaction hazard at urban scale     

Lai  C. G.  Bozzoni  F.  Conca  D.  Famà  A.  Özcebe  A. G.  Zuccolo  E.  Meisina  C.  Bonì  R.  Bordoni  M.  Cosentini  R. M.  Martelli  L.  Poggi  V.  Viana da Fonseca  A.  Ferreira  C.  Rios  S.  Cordeiro  D.  Ramos  C.  Molina-Gómez  F.  Coelho  C.  Logar  J.  Maček  M.  Oblak  A.  Ozcep  F.  Bozbey  I.  Oztoprak  S.  Sargin  S.  Aysal  N.  Oser  C.  Kelesoglu  M. K. 《Bulletin of Earthquake Engineering》2021,19(10):4013-4057

Bulletin of Earthquake Engineering - Microzonation for earthquake-induced liquefaction hazard is the subdivision of a territory at a municipal or submunicipal scale in areas characterized by the...  相似文献   

Megazonation of earthquake-induced soil liquefaction hazard in continental Europe     

Bozzoni  F.  Bonì  R.  Conca  D.  Lai  C. G.  Zuccolo  E.  Meisina  C. 《Bulletin of Earthquake Engineering》2021,19(10):4059-4082

Bulletin of Earthquake Engineering - Mapping large territories for earthquake-induced soil liquefaction hazard may sound like an oxymoron since soil liquefaction is by itself a spatially highly...  相似文献   

Annual and spatial variations of chemical and physical properties in the Ross Sea surface waters (Antarctica)     

Serena Massolo  Roberta Messa  Paola Rivaro  Riccardo Leardi 《Continental Shelf Research》2009

Temperature, salinity, meltwater percentage, water column stability, dissolved oxygen and nutrients were measured in seawater samples collected at three fixed depths (0, 20, 100 m) in 104 stations located in three different areas of the Ross Sea (Antarctica), during four Italian Antarctic surveys carried out between 1998 and 2006. Nutrient data were used to quantify the nutrient removal, which appears particularly high in 2006, especially in polynya area. The N:P and Si:N disappearance ratios were studied to estimate the dominant phytoplanktonic community. No significant differences in the nutrient drawdown ratio were observed, in fact the N:P ratio was always below the Redfield standard ratio.  相似文献   

Active faulting and continental slope instability in the Gulf of Patti (Tyrrhenian side of NE Sicily,Italy): a field,marine and seismological joint analysis     

F. Cultrera  G. Barreca  P. Burrato  L. Ferranti  C. Monaco  S. Passaro  F. Pepe  L. Scarfì 《Natural Hazards》2017,86(2):253-272

The Gulf of Patti and its onshore sector represent one of the most seismically active regions of the Italian Peninsula. Over the period 1984–2014, about 1800 earthquakes with small-to-moderate magnitude and a maximum hypocentral depth of 40 km occurred in this area. Historical catalogues reveal that the same area was affected by several strong earthquakes such as the Mw = 6.1 event in April 1978 and the Mw = 6.2 one in March 1786 which have caused severe damages in the surrounding localities. The main seismotectonic feature affecting this area is represented by a NNW–SSE trending right-lateral strike-slip fault system called “Aeolian–Tindari–Letojanni” (ATLFS) which has been interpreted as a lithospheric transfer zone extending from the Aeolian Islands to the Ionian coast of Sicily. Although the large-scale role of the ATLFS is widely accepted, several issues about its structural architecture (i.e. distribution, attitude and slip of fault segments) and the active deformation pattern are poorly constrained, particularly in the offshore. An integrated analysis of field structural geology with marine geophysical and seismological data has allowed to better understand the structural fabric of the ATLFS which, in the study area, is expressed by two major NW–SE trending, en-echelon arranged fault segments. Minor NNE–SSW oriented extensional structures mainly occur in the overlap region between major faults, forming a dilatational stepover. Most faults display evidence of active deformation and appear to control the main morphobathymetric features. This aspect, together with diffused continental slope instability, must be considered for the revaluation of the seismic and geomorphological hazard of this sector of southern Tyrrhenian Sea.  相似文献   

Tracking the lithium isotopic evolution of the mantle using carbonatites     

Ralf Halama  William F. McDonough  Roberta L. Rudnick  Keith Bell 《Earth and Planetary Science Letters》2008,265(3-4):726-742

Carbonatites are mantle-derived, intraplate magmas that provide a means of documenting isotopic variations of the Earth's mantle through time. To investigate the secular Li isotopic evolution of the mantle and to test whether Li isotopes document systematic recycling of material processed at or near the Earth's surface into the mantle, we analyzed the Li isotopic compositions of carbonatites and spatially associated mafic silicate rocks. The Li isotopic compositions of Archean (2.7 Ga) to Recent carbonatites (δ⁷Li = 4.1 ± 1.3 (n = 23, 1σ)) overlap the range typical for modern mantle-derived rocks, and do not change with time, despite ongoing crustal recycling. Thus, the average Li isotopic composition of recycled crustal components has not deviated greatly from the mantle value (~ + 4) and/or Li diffusion is sufficiently fast to attenuate significant heterogeneities over timescales of 10⁸ years. Modeling of Li diffusion at mantle temperatures suggests that limited δ⁷Li variation in the mantle through time reflects the more effective homogenization of Li in the mantle compared to radiogenic isotope systems. The real (but limited) variations in δ⁷Li that exist in modern mantle-derived magmas as well as carbonatites studied here may reflect isotopic fractionation associated with shallow-level processes, such as crustal assimilation and diffusive isotopic fractionation in magmatic systems, with some of the scatter possibly related to low-temperature alteration.  相似文献   

(137)Cs baseline levels in the Mediterranean and Black Sea: a cross-basin survey of the CIESM Mediterranean Mussel Watch programme     

Thébault H  Rodriguez Y Baena AM  Andral B  Barisic D  Albaladejo JB  Bologa AS  Boudjenoun R  Delfanti R  Egorov VN  El Khoukhi T  Florou H  Kniewald G  Noureddine A  Patrascu V  Pham MK  Scarpato A  Stokozov NA  Topcuoglu S  Warnau M 《Marine pollution bulletin》2008,57(6-12):801-806

The common mussel Mytilus galloprovincialis was selected as unique biomonitor species to implement a regional monitoring programme, the CIESM Mediterranean Mussel Watch (MMW), in the Mediterranean and Black Seas. As of today, and upon standardization of the methodological approach, the MMW Network has been able to quantify (137)Cs levels in mussels from 60 coastal stations and to produce the first distribution map of this artificial radionuclide at the scale of the entire Mediterranean and Black Seas. While measured (137)Cs levels were found to be very low (usually < 1 Bq kg(-1) wet wt) (137)Cs activity concentrations in the Black Sea and North Aegean Sea were up to two orders of magnitude higher than those in the western Mediterranean Basin. Such effects, far from representing a threat to human populations or the environment, reflect a persistent signature of the Chernobyl fallout in this area.  相似文献