Complex Semblance and Its Application Abstract Semblance, a measure of multi-trace coherence, has been used extensively in seismic data processing and interpretation such as velocity analysis and fault detection. The traditional algorithm has a difficulty at zero-crossings of seismic recordings. This problem is alleviated by applying a smoothing window at the cost of losing vertical resolutions. In this paper, we improve the algorithm by computing semblance from complex traces. Our initial results show that the complex semblance is smooth at zero-crossings. Because the smoothing time window becomes unnecessary, the higher vertical resolution can be achieved by using small windows or none. Some geological features, like faults and unconformities, appear clearer and easier to identify with the complex semblance. As the advantages are obvious and the implementation is straight-forward with the Hilbert transform, this new algorithm may replace the traditional one in future applications.

Differentiation of Continental Subduction Mode: Numerical Modeling Abstract The convergence of the multi-layered continental lithospheres with variable and complex thermal and rheological properties results in various modes of continental collision with distinct deformation behavior of the lithospheric mantle. Using high-resolution thermo-mechanical numerical models, we systematically investigated the effects of crustal rheological strength and the convergence rate on the continental subduction mode. The model results reveal three basic modes of continental subduction, including slab break-off, steep subduction and continental flat-slab subduction. Whether lithospheric mantle of the overriding plate retreats or not during convergence enables the division of the first two modes into two sub-types, which are dominated by the crustal rheological strength. The mode of slab break-off develops under the conditions of low/moderate rheological strength of the continental crust and low convergence rate. In contrast, continental flat-slab subduction favors the strong crust and the high convergence rate. Otherwise, continental steep subduction occurs. The numerical results provide further implications for Geodynamics conditions and physical processes of different modes of continental collision that occur in nature.

Enhanced Degradation of Methyl Parathion in the Ligand Stabilized Soluble Mn(III)-Sulfite System Abstract The ligand-stabilized soluble Mn(III) recognized as active intermediate can potentially mediate the attenuation of contaminants. In this study, the abiotic degradation behaviors of methyl parathion in the ligand stabilized Mn(III)-sulfite system were investigated. The results showed that the yield of soluble Mn(III) produced from the redox reaction of MnO2 and oxalic acid was dependent linearly on the dosage of MnO2 and caused the decomposition of methyl parathion up to 50.1% in Mn(III)-sulfite system after 30 minutes. The fitted pseudo-first-order reaction constants of methyl parathion degradation increased with the increasing of the amount of produced Mn(III) but was not effected linearly by the addition of sulfite. Other ligands, including pyrophosphate and oxalic acid, acted as effective complexing agents to stabilize soluble Mn(III), and exhibited competitive effect on methyl parathion degradation with sulfite. The formation of Mn(III)-sulfite complexes is the critical step in the system to produce abundant reactive oxygen species identified as SO3•- to facilitate methyl parathion degradation. The hydrolysis and oxidation of methyl parathion were acknowledged as two primary transformation mechanisms in Mn(III)-sulfite system. These findings indicate that naturally ligands-stabilized soluble Mn(III) can be generated and could oxidatively decompose organophosphate pesticides such as methyl parathion.

Geochemical and Mineralogical Investigation on Different Types of Cenozoic Basalts in the Sanshui Basin: Implications for Magma Mixing Processes Abstract Two kinds of basalts with different chemical compositions were obtained in the Sanshui Basin, they share the same eruption period. Although they have significant differences in major and trace element concentrations, their isotopic ratios suggest a similar magma source. Based on mineral geochemical analysis, orthopyroxene with reaction rim and zoned clinopyroxene are observed in Zidong (ZD) basalts, but not found in Wangjiegang (WJG) basalts. Linear scanning of these minerals suggests compositional variation between within-plate tholeiite and within-plate alkali-basalt. Presence of a double-layer magma chamber under the Sanshui Basin, and occurrence of magma mixing between upper and lower chambers is proposed. This magma mixing leads to different chemical composition and mineral constitution of two kinds of basalts, as well as reaction rim and compositional variation of minerals in ZD basalts.

Timing of Lithospheric Extension in Northeastern China: Evidence from the Late Mesozoic Nianzishan A-Type Granitoid Complex Abstract New zircon U-Pb dates obtained by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), whole-rock geochemical data and Sm-Nd and Rb-Sr isotopic data are presented for miarolitic alkaline granites, porphyritic syenite and rhyolites of the Nianzishan A-type granitoid complex (NAGC) in the Great Xing’an Range-Songliao Basin in Northeast (NE) China. New crystallization ages of 112.95±0.93 and 114.1±1.71 Ma for granite and 118.6±0.51 Ma for porphyritic syenite were determined by high-precision LA-ICP-MS. The εNd(t) of the rocks range from +1.85 to +2.06, with Nd model ages (TDM1) from 671 to 821 Ma, indicating that the NAGC originated from juvenile source rocks and exhibits geochemical characteristics of A1- and AA-type granite which formed in an extensional setting. We attribute the magmatism to regional extension and lithospheric thinning caused by the subduction of the western Pacific Plate about 120 to 100 Ma.

Parallel Seismic Modeling Based on OpenMP+AVX and Optimization Strategy Abstract This paper describes parallel simulation of the memory/computation-intensive acoustic wave equation with CPU template buffer optimization. Considering the 8-core CPU shared storage platform as an example, we obtain a one-time speed-up ratio of 6.7× compared with the serial program by using a coarse-grained OpenMP parallel scheme. Then, data is vectorized on the template buffer using the single instruction-multiple data (SIMD) technique to further exploit the computing potential of the CPUs. We apply an 8-channel parallel vector to simulate seismic wavefields with the 256-bit advanced vector extensions (AVX) instruction set. This increases the computing bandwidth, thus eliminating a significant volume of the computing instructions and obtaining a secondary speed-up ratio of 3–7×. In addition, we use 32-byte data alignment, shortest data direction vectorization, and loop tiling optimization algorithm to achieve faster program execution. Finally, we analyze the factors affecting the secondary speed-up of AVX through three-dimensional modeling experiments with the salt model. The results indicate that the memory, cache, and register can better cooperate with each other and the speed-up is increased by optimizing the AVX algorithm.

Identification of Concealed Faults in a Grassland Area in Inner Mongolia, China, Using the Temperature Vegetation Dryness Index Abstract Fault identification in vegetated area (e.g., grassland) is a major challenge compared to that in outcrop areas. To identify concealed faults in a grassland covered area, a hybrid method combining the temperature vegetation dryness index (TVDI) and the singularity index was proposed in this paper to extract TVDI anomalies associated with concealed fractures in the Sonid Left Banner Grassland, Inner Mongolia, North China. In the triangle space of LST/NDVI (land surface temperature/normalized difference vegetation index), scattered points were concentrated in the areas of partial and full cover, while few data points were in the areas of bare soil with low values of NDVI and high values of LST; this result is consistent with the semiarid grassland landscape of the study area. Although TVDI imaging shows an obvious linear pattern with an NE-NNE trend, which indicates the existence of concealed faults, the surrounding background weakened and reduced the significance of the anomalies. To better delineate the concealed faults, the singularity index was employed to remove the influence of the background and enhance the TVDI anomalies associated with the concealed faults. The TVDI imaging and singularity index mapping showed NNE and NE orientations; this finding is consistent with the regional tectonic framework. Geological mapping footprints showed that the hybrid method is useful to identify concealed faults in covered areas of grassland.

Diabase Sills in the Outer Zone of the Emeishan Large Igneous Province, Southwest China: Petrogenesis and Tectonic Implications Abstract Compositionally and texturally zoned diabase dykes and sills occur in the outer zone of the Emeishan large igneous province (ELIP) in the southern Guizhou Province, Southwest China. Based on the detailed petrology, whole rock geochemistry, zircon U-Pb geochronology and Hf isotopes and clinopyroxene mineral compositions studies, we investigate a representative diabase sill in the Luodian region with a view to understanding its petrogenesis and tectonic implications. Formed as composite zoned sub-volcanic intrusion, the diabase sill is characterized by gabbros and diabases in the inner zone and amygdaloidal diabases sporadically in the chilled zone within the upper sill margin. The diabasic and gabbroic rocks are composed of quartz-free and quartz-bearing groups. The quartz-free group rocks have low SiO2 (45.7 wt.%–49.5 wt.%), moderate MgO (5.66 wt.%–7.88 wt.%), high TiO2 (2.54 wt.%–3.65 wt.%), and Ti/Y values (536–747), corresponding to high-Ti type rocks. The quartz-bearing group rocks have higher SiO2 (49.8 wt.%–51.7 wt.%) and lower MgO (4.23 wt.%–4.74 wt.%), higher TiO2 (3.16 wt.%–3.63 wt.%), but lower Ti/Y values (399–419) than the quartz-free group ones, and thus belong to the low-Ti type. Both groups of rocks are enriched in LREE and LILE with negative Nb-Ta anomalies, and show broad tholeiitic affinity. The precursor magma of the high-Ti rocks might have originated from a source composed of mantle plume and subcontinental lithosphere mantle components, with minor crustal contamination during ascending. The magma of the low-Ti rocks was produced by mingling of the high-Ti diabasic rocks with minor injected intermediate-acidic magma plugs or blebs, suggesting magma mingling as one of the effective ways to change the high-Ti to low-Ti rocks of the ELIP. The diabasic sill underwent a rapid cooling event probably in response to a rapid tectonic uplift event, which probably occurred in the waning stage of ELIP during transition between the Middle and Late Permian after the domal uplift induced by the mantle-plume or in the Late Jurassic.

Formation Mechanism of Beach Rocks and Its Controlling Factors in Coral Reef Area, Qilian Islets and Cays, Xisha Islands, China Abstract Beach rock, which forms at the intertidal zone, is a natural barrier to protect beach and island from wave erosion. The formation mechanism of beach rocks is significant in the study of surface carbonate diagenesis and protection of island. Beach rocks in Qilian Islets and Cays were formed about 500–700 a BP, neither its composition nor sedimentary structure experienced intense post-reformation. Beach rocks in Qilian Islets and Cays are mainly composed of reef-building skeletal fragments and bioclasts without terrigenous sediments. This study focused on the types and morphologies of cements in beach rocks of Qilian Islets and Cays, and its cementation mechanisms and influencing factors. Biological activities, such as micritization caused by microbial activities and algae binding action, play an important role in the initial stage of bioclast transformation and promote the subsequent early marine and early meteoric cementation. Acicular aragonite induced by early marine cementation is well developed in beach rocks, especially in those samples from Medium Islet. Early meteoric cementation is not common as marine cementation, generally presenting granular and meniscus cements. The main factors affecting the formation and development of beach rocks in Qilian Islets and Cays include sediment source, hydrodynamic condition, climate, sea level change and anthropogenic impacts.

An Upper Crustal Ophiolite Remnant within the Feather River Ultramafic Belt, California: Tectonomagmatic Origins and Implications for Its Evolution Abstract The 150-km-long Feather River ultramafic belt (FRB) of the northern Sierra Nevada, California, consists of serpentinized ultramafic rocks, gabbroic rocks, with lesser amounts of amphibolitic rocks. The gabbroic rocks contain metagabbro and dikes within it. Based on the electron microprobe analyses, the metagabbro consists of typical igneous composition for clinopyroxene and early hornblende, indicating that they bear low grade metamorphism. The gabbroic rocks show Nb and Ta depletion in primitive-mantle normalized plots that is similar to typical island arc rocks. We present that the metagabbro within the ultramafic rocks is forming in the suprasubduction zone setting. Tectonic models are presented for the metagabbro and amphibolitic rocks in FRB. The low P burial metamorphism of the upper plate metagabbro and the high grade amphibolitic rocks are typical of relationships of upper plate ophiolites to metamorphic soles. The amphibolitic rocks record as metamorphic sole forming during subduction initiation beneath the ultramafic rocks and metagabbro. The unusual and protracted tectonic history of the FRB is similar to other ophiolite belts of the Cordillera of California but differs in the lack of crustal rocks.