Xu Shijin

A neural network algorithm to retrieve nearsurface air temperature from landsat ETM+ imagery over the hanjiang river basin, china

An algorithm based on a BP neural network for retrieval of near-surface daily mean, maximum and minimum air temperature from remotely sensed data was developed in this paper. The algorithm was tested to map air temperature by integrating Landsat Enhanced Thematic Mapper Plus (ETM+) derived surface information with GIS provided meteorological parameters with a BP neural network over the upstream Basin of the Hanjiang River, Southwestern China. The parameters involved in the training of the BP neural network for inversion of air temperature can be subdivided into six groups, each was used to represent different data sources for testing the sensitivity of these variables on the near-surface air temperature retrieved. These parameters are remotely sensed albedo, NDVI, layered meteorological data of station observed daily mean, maximum and minimum are temperature provided by GIS as well as the DEM of the study site. Five criterions, namely Mean Error (ME), Mean Absolute Error (MAE), Root Mean Squared Error (RMSE), Mean Relative Error (MRE) and correlation coefficient (R2) were utilized to evaluate the performance of the proposed algorithm by comparing the retrieved and the observed air temperature quantitatively. Systematic analyses suggested that the satisfied retrieval of daily mean and maximum near-surface air temperature can be achieved with MRE of 3.02% and 2.23% and RMSE of 0.93 and 0.9 respectively. However, only when all the parameters including daily mean and maximum near- surface air temperature were used for training the BP neural network, the daily minimum air temperature could be retrieved with the best MRE of 8.31%. From this study, it can be concluded that the BP neural network integrating with surface meteorological observations might be a promising approach for retrieving near-surface air temperature with reliable accuracy.

Oxygen isotope study of the Suzhou granite

Oxygen isotope studies of the Suzhou granite have been made based on drill-hole samples. In the inner part, the δ18O values are less variable either in the whole-rock, quartz or in feldspar. Oxygen isotopic compositions are in equilibrium between coexisting quartz and feldspar. Data points from the inner part are plotted in a small area in the δ18OQ-δ18Of diagram, indicating that this part has not been affected by meteoric hydrothermal fluids. But the whole-rock δ18O values of the marginal part vary greatly. Oxygen isotopic compositions are in extreme disequilibrium between quartz and feldspar. Data points from the marginal part are displayed with a nearly vertical slope in the δ18OQ-δ18Of diagram, implying that rocks of this part are affected by the meteoric hydrothermal fluids. Extreme water-rock interactions lead to mineralizations of rare-elements (Nb, Ta, as well as Zr, Hf, Th) in the marginal part. Source materials of the Suzhou granite are also discussed in this paper.

Tantalite in Suzhou granite: Mineralogy and geological implications

Tantalite, occurring as intergranular tabular crystals, was reported for the first time in the Suzhou granite. Electron microprobe analyses show that it is rich in W and Ti, with a Ta/(Ta + Nb) ratio ranging from 0.5 to 0.73 and a Mn/(Mn + Fe) ratio between 0.20 and 0.40. It is structurally distinct from isomorphic tapiolite by a remarked Ag Raman peak at 880 cm−1. The associated zircon is striking by significant enrichment of Hf, with the HfO2 content amounting up to 35% – 40%. The discovery of tantalite suggests that the Suzhou granite should be classified as a S-type granite instead of A-type as considered previously.

Minerogenesis of Shilu iron ores with special reference to Sm-Nd isotope geochemical characteristics of Shilu Group bimodal volcanic rocks in Hainan Island

Presented in this paper are Sm-Nd isotope and major, trace and rare-earth element analyses of bimodal volcanic rocks of the Shilu Group and other stratigraphic units in northwestern Hainan Island, South China. It is shown that there are some N-MORB-type basalts (spilites) in the western part of the bimodal volcanic belt, in addition to some E-MORB-type and initial rift-type tholeiites (IRT) in the middle and eastern parts. Sm-Nd model ages of these basalts range from 545 Ma to 460 Ma. The other extremes of the bimodal volcanics are porphyritic quartz rhyolites. which are characteristic of crustal material source. Sm-Nd model ages of the rhyolites range from 1562 Ma to 1371 Ma. The bimodal volcanic rocks are almost distributed in rifts or faulted depressions, as well as in the Upper Paleozoic rift of Hainan Island.Tholeiites of the Shilu Group can be compared with Cenozoic basalts in the middle and southern parts of the Red Sea Rift Belt in petrology, elemental geochemistry and Sm-Nd isotope geology. Shilu iron ores are closely associated with N-MORB-type basalts located in the western bimodal volcanic belt. It is very interesting to note that the Shilu Fe-Co-Cu deposit can also be compared with Atlantis II Deep in the Red Sea Rift Belt. Therefore, the present authors believe that the Shilu deposit is a kind of hydrothermal deposit related to ocean volcanic belt, where the geotectonic setting belongs to initial extensional rifts in the oceanic crust. On the other hand, the largest Fe-Co-Cu ore deposit in China used to be influenced by Hercynian granites after mineralization, as is clearly observed on both ε Nd (T)-1/Nd and ε Nd (T)-147Sm/144Nd diagrams.