Time filter

Source Type

Zhou J.-L.,China University of Geosciences | Shao S.,China University of Geosciences | Shao S.,China Aerospace Geophysical Survey and Remote Sensing Center for Land and Resources | Luo Z.-H.,China University of Geosciences | Rasoamalala V.,Directorate of Geology
Precambrian Research | Year: 2015

Tectonic setting of the ca. 840-760Ma Imorona-Itsindro Suite throughout central Madagascar is critical to understanding Madagascar-India correlation in pre-Gondwana time and the paleogeography of the rifting Rodinia. Here, we present new geochronological and geochemical data for gabbros of this suite from the Ambatondrazaka area in east-central Madagascar. SIMS U-Pb zircon dating reveals that the gabbros emplaced between ca. 797 and 772Ma. They define a typical tholeiitic trend on the AFM and FeOT/MgO vs. SiO2 plots, which is confirmed by the occurrence of layered Fe-Ti-V oxide mineralization. Owing to the high-K nature, they were previously misinterpreted as a "calc-alkaline" association produced in a mature continental arc. Indeed, it implies in return an intra-plate affinity for tholeiitic rocks. Their high Zr/Y, La/Y and Ti/V ratios differ from those of typical arc and back-arc mafic suites but are compatible with an intra-plate setting. Additionally, they are characterized by low AlZ/TiO2 ratios in clinopyroxene, further supporting an intra-plate environment. The negative e{open}Nd(t) (-8.4 to -5.1) and zircon e{open}Hf(t) (-6.84 to -3.08) values, together with enriched trace element signatures, indicate their derivation from an enriched lithospheric mantle source. Considering the initial 87Sr/86Sr ratios (0.705409-0.706892) and Nd modal ages (~2.1-2.4Ga), we postulate that this mantle reservoir has EM1-type isotopic characteristics and was enriched by a Late Neoarchean "super accretion event". Taken together, our results question the existence of the Betsimisaraka Suture but support the proposal that the Malagasy Shield and the Dharwar Craton of India are parts of the same entity - the Greater Dharwar Craton. Within this framework, the widely cited hypothesis that an extensive Andean-type arc was developed along the northwestern margin of the rifting Rodinia is challenged, at least that the magmatic arc did not extend to the Malagasy Shield. © 2014 Elsevier B.V. Source

Song R.,CAS Institute of Remote Sensing | Song R.,University of Chinese Academy of Sciences | Guo H.,CAS Institute of Remote Sensing | Liu G.,CAS Institute of Remote Sensing | And 2 more authors.
IEEE Geoscience and Remote Sensing Letters | Year: 2014

The Goldstein filter is one of the most commonly used synthetic aperture radar (SAR) interferogram filters. This letter proposes a new method to find filter parameters of the Goldestein filter based on noise level derived by the empirical mode decomposition (EMD) method. The filtering parameter determined by this method has a definite physical meaning.We used bidimensional empirical mode decomposition (BEMD) to extract features of an interferometric phase image into multiple scales of spatial frequencies, called intrinsic mode functions (IMF). We constructed a pseudo-SNR (signal-to-noise ratio) with the given IMF component, then the new parameter was applied to the Goldstein filtering method in place of the original fixed value ascertained artificially. The results from simulation and real data show that the performance of the new algorithm outperforms the original Goldstein filter, and its enhanced version, the Baran filter. The quantitative evaluation also shows that modification based on the EMD proposed in our paper minimizes the loss of phase while still reducing the level of noise in an interferogram. © 2013 IEEE. Source

Luo M.F.,China University of Geosciences | Mo X.X.,China University of Geosciences | Yu X.H.,China University of Geosciences | Li X.W.,China University of Geosciences | And 2 more authors.
Acta Petrologica Sinica | Year: 2014

A large number of granites are widely distributed in the East Kunlun Orogen. Previous work indicates that the granites are mainly formed in the Late Permian-Middle Triassic and Late Triassic two periods. In this paper, we reporter Xiangride intrusion located in the eastern part of the East Kunlun orogen, which is composed of monzogranites and granodiorites, The LA-ICPMS U-Pb analyses suggest that the formation ages of granodiorites and monzogranites are 223.2 ± 1.7Ma and 220.6 ± 1.5Ma respectively. Granodiorites and monzogranites are characterized by enrichment of large lithophile elements(LILE, such as Rb, Th and K) and light rare earths element(LREE), significant negative anomalies of HFSE (eg. Nb, Ta, Ti and P), relatively high ISr values(0.70820 ∼ 0.71148), low εNd(t) values (-6.4 ∼ -3.8), and the older Nd isotopic model ages(the t2DM values are 1.5 ∼ 1.7Ga). The geochemical characteristics of the granites indicate that Xiangride intrusion is originated from partial melting of ancient crust which is resulted from magma underplating. Since the Late Hercynian mantle-derived basaltic magma underplated bottom of lower crust constantly and made it thickened, finally, the thickened crust occurred delamination in the Late Triassic. The subduction of the A'nimaque paleo-ocean was lasting up to the Early Triassic, and the Late Triassic witnessed the intracontinental collision. The systematic discrepancies between the Late Triassic granites and the Late Permian-Middle Triassic granites, in terms of the abundance of MMEs and magma mixing, can be explained by the different contribution from mantle materials and the diverse paths of the experienced MASH processes. Source

Li L.,China Aerospace Geophysical Survey and Remote Sensing Center for Land and Resources
Proceedings - 2010 2nd WRI World Congress on Software Engineering, WCSE 2010 | Year: 2010

Based on the principle of spectral responses of remote sensing, using multi-phases TM data and measured points as basic data, the main methods are correlation analysis on spectral data, regression analysis and fitting inversion in the study area of Zhabuye salt lake that lies in Tibet autonomous region. This paper had achieved distributions of the salt content in the lake, meanwhile, generated their contour maps reflecting salt content with method of dual inline encryption. By the method of principal component analysis, extracted salt information on the basis of 3-D salt index. Among those components, the first component is the one reflecting salt content. At last, the paper established salt content model for the salt lake, which is proved to be quadratic polynomial fitting. At last, inverse the salt content models by colors slice. Compare between inversion results and measured data on the aspects of salt contour map, it proved that inversion effect meet the distribution of measured date. © 2010 IEEE. Source

Chen W.,Wuhan University | Chen W.,Key Laboratory of Disaster Reduction | Li X.,Wuhan University | Wang Y.,State Key Laboratory of Biogeology and Environmental Geology | And 2 more authors.
Environmental Earth Sciences | Year: 2013

The objective of this study is to map landslide susceptibility in Zigui segment of the Yangtze Three Gorges area that is known as one of the most landslide-prone areas in China by using data from light detection and ranging (LiDAR) and digital mapping camera (DMC). The likelihood ratio (LR) and logistic regression model (LRM) were used in this study. The work is divided into three phases. The first phase consists of data processing and analysis. In this phase, LiDAR and DMC data and geological maps were processed, and the landslide-controlling factors were derived such as landslide density, digital elevation model (DEM), slope angle, aspect, lithology, land use and distance from drainage. Among these, the landslide inventories, land use and drainage were constructed with both LiDAR and DMC data; DEM, slope angle and aspect were constructed with LiDAR data; lithology was taken from the 1:250,000 scale geological maps. The second phase is the logistic regression analysis. In this phase, the LR was applied to find the correlation between the landslide locations and the landslide-controlling factors, whereas the LRM was used to predict the occurrence of landslides based on six factors. To calculate the coefficients of LRM, 13,290,553 pixels was used, 29.5 % of the total pixels. The logical regression coefficients of landslide-controlling factors were obtained by logical regression analysis with SPSS 17.0 software. The accuracy of the LRM was 88.8 % on the whole. The third phase is landslide susceptibility mapping and verification. The mapping result was verified using the landslide location data, and 64.4 % landslide pixels distributed in "extremely high" zone and "high" zone; in addition, verification was performed using a success rate curve. The verification result show clearly that landslide susceptibility zones were in close agreement with actual landslide areas in the field. It is also shown that the factors that were applied in this study are appropriate; lithology, elevation and distance from drainage are primary factors for the landslide susceptibility mapping in the area, while slope angle, aspect and land use are secondary. © 2012 Springer-Verlag Berlin Heidelberg. Source

Discover hidden collaborations