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There is considerable controversy over the nature of geophysically recognized low-velocity-high-conductivity zones (LV-HCZs) within the Tibetan crust, and their role in models for the development of the Tibetan Plateau. Here we report petrological and geochemical data on magmas erupted 4.7-0.3 Myr ago in central and northern Tibet, demonstrating that they were generated by partial melting of crustal rocks at temperatures of 700-1,050°C and pressures of 0.5-1.5 GPa. Thus Pliocene-Quaternary melting of crustal rocks occurred at depths of 15-50 km in areas where the LV-HCZs have been recognized. This provides new petrological evidence that the LV-HCZs are sources of partial melt. It is inferred that crustal melting played a key role in triggering crustal weakening and outward crustal flow in the expansion of the Tibetan Plateau.

Geophysical data illustrate that the Indian continental lithosphere has northward subducted beneath the Tibet Plateau, reaching the Bangong–Nujiang suture in central Tibet. However, when the Indian continental lithosphere started to subduct, and whether the Indian continental crust has injected into the mantle beneath southern Lhasa block, are not clear. Here we report new results from the Quguosha gabbros of southern Lhasa block, southern Tibet. LA-ICP-MS zircon U–Pb dating of two samples gives a ca. 35 Ma formation age (i.e., the latest Eocene) for the Quguosha gabbros. The Quguosha gabbro samples are geochemically characterized by variable SiO2 and MgO contents, strongly negative Nb–Ta–Ti and slightly negative Eu anomalies, and uniform initial 87Sr/86Sr (0.7056–0.7058) and εNd(t) (− 2.2 to − 3.6). They exhibit Sr–Nd isotopic compositions different from those of the Jurassic–Eocene magmatic rocks with depleted Sr–Nd isotopic characteristics, but somewhat similar to those of Oligocene–Miocene K-rich magmatic rocks with enriched Sr–Nd isotopic characteristics. We therefore propose that an enriched Indian crustal component was added into the lithospheric mantle beneath southern Lhasa by continental subduction at least prior to the latest Eocene (ca. 35 Ma). We interpret the Quguosha mafic magmas to have been generated by partial melting of lithospheric mantle metasomatized by subducted continental sediments, which entered continental subduction channel(s) and then probably accreted or underplated into the overlying mantle during the northward subduction of the Indian continent. Continental subduction likely played a key role in the formation of the Tibetan plateau at an earlier date than previously thought.

Little is known about the detailed processes associated with the transition from oceanic to continental lithosphere subduction in the Gangdese Belt of southern Tibet (GBST). Here, we report zircon U–Pb age, major and trace element and Sr–Nd–Hf isotopic data for Late Cretaceous–Early Oligocene (~ 91–30 Ma) intermediate-acid intrusive rocks in the Chanang–Zedong area immediately north of the Yarlung–Tsangpo suture zone. These rocks represent five magmatic episodes at ~ 91, ~ 77, ~ 62, ~ 48, and ~ 30 Ma, respectively. The 91–48 Ma rocks have slightly lower initial 87Sr/86Sr (0.7037 to 0.7047), and higher εNd(t) (+ 1.8 to + 4.3) and εHf(t) (+ 3.5 to + 14.7) values in comparison with those (0.7057 to 0.7062, − 3.3 to − 2.5 and + 2.2 to + 6.6) of the ~ 30 Ma intrusive rocks. The ~ 91, ~ 62 and ~ 30 Ma rocks are geochemically similar to slab-derived adakites. The ~ 91 Ma Somka adakitic granodiorites were likely derived by partial melting of the subducting Neo-Tethyan oceanic crust with minor oceanic sediments, and the ~ 91 Ma Somka dioritic rocks with a geochemical affinity of adakitic magnesian andesites likely resulted from interactions between adakitic magmas and overlying mantle wedge peridotite. The ~ 77 Ma Luomu diorites were probably generated by partial melting of juvenile basaltic lower crust. The ~ 62 Ma Naika and Zedong adakitic diorites and granodiorites were likely generated mainly by partial melting of thickened juvenile mafic lower crust but the source region of the Zedong adakitic rocks also contained enriched components corresponding to Indian continental crust. The ~ 48 Ma Lamda granites were possibly generated by melting of a juvenile basaltic crust. The younger (~ 30 Ma) Chongmuda adakitic quartz monzonites and minor granodiorites were most probably derived by partial melting of Early Oligocene northward-subducted Indian lower crust beneath the southern Lhasa Block. Taking into account the regional tectonic and magmatic data, we suggest that the Gangdes

Cenozoic adakitic rocks in the Lhasa block (southern Tibet) have been widely used to trace the lateral extent of crustal thickening. However, their petrogenesis remains controversial. Here, we report geochronological and geochemical data for the Napuri intrusive rocks in the core area of the Quxu batholith, southern Lhasa. Zircon U–Pb dating suggests that they were generated at approximately 48 Ma. The studied samples show significant geochemical variations, manifested by the coexistence of three types of igneous rocks. Groups I and II rocks exhibit variable and high SiO2 (66.4–73.9 wt.%), high Al2O3 (14.0–17.4 wt.%), K2O (3.9–5.3 wt.%), Sr (273–718 ppm) and Sr/Y (18.3 to 81.3) values, and low Y (3.6 to 16 ppm), heavy rare earth element (REE) (e.g., Yb = 0.48 to 1.8 ppm), MgO (0.4–1.0 wt.%), Cr (2.9–7.4 ppm) and Ni (1.6–4.5 ppm) contents, which are similar to those of thickened lower crust-derived adakitic rocks. The Group I rocks show higher Sr/Y (77.5–81.3) ratios and lower total REE (55.5–63.2 ppm) contents with clearly positive Eu and Sr anomalies, whereas the Group II rocks have relatively lower Sr/Y (18.3–65.7) ratios and higher total REE (115–375 ppm) contents with negligible or slightly negative Eu and Sr anomalies. Group III rocks have the highest SiO2 (74.5–76.0 wt.%), Y (17.0–23.7 ppm) and Yb (2.91–3.30 ppm) contents, and the lowest Al2O3 (12.5–13.2 wt.%), Sr (81.3–141 ppm) and Sr/Y (4.8–5.9) values with distinctly negative Eu and Sr anomalies. Compared with the Jurassic–Cretaceous granitoids in southern Lhasa, the relative enrichment in Sr–Nd–Hf isotopic compositions ((87Sr/86Sr)i = 0.7049–0.7055, εNd(t) = − 0.3 ± 0.7 and εHf(t)zircon = + 3.6 ± 11.4) for the Napuri intrusive rocks indicates that they likely contained Indian continental components. The Group I and Group II rocks most probably originated from thickened mafic lower crust (amphibolite eclogites or garnet amphibolites) with garnet + rutile ± plagioclase as residual minerals in the source at >

At more than 500 km in length, the mainly Jurassic–Early Eocene Gangdese batholith is one of the most important constituents of the southern Lhasa sub-block and provides an ideal site for study of Tibetan orogenesis. Recent studies on Gangdese intermediate-felsic intrusive rocks, mainly granites, demonstrate that remarkable crustal growth as well as an early Late Cretaceous (ca. 100–80 Ma) magmatic “flare-up” event occurred in southern Tibet. However, the mechanism that drove this magmatic event and its relationship to crustal growth event are not yet clear. Here, we report detailed petrological, geochronological, geochemical and Sr–Nd–Hf isotopic data for recently identified norites and hypersthene-bearing hornblendites in the Milin area, southern Lhasa sub-block. These mafic rocks are dated at early Late Cretaceous (ca. 93 Ma), and are characterized by relatively uniform Sr–Nd–Hf isotopic compositions ((87Sr/86Sr)I = 0.7042 to 0.7047, ((87Sr/86Sr)i = 0.7042 to 0.7047, εNd(t) = + 2.9 to + 3.6 and εHf(t)zircon = + 10.9 to + 17.0), suggesting that they evolved from similar parental magmas.The Milin norites and hornblendites are likely to be the products of mineral fractionation and accumulation from a common parental magma during the early and late stages of the magma evolution, respectively. Thermometric calculations indicate that pyroxenes from the Milin norites have high crystallization temperatures (1240–1349 °C). The parental magmatic compositions calculated from pyroxene trace element compositions in the Milin norites show slightly flat to enriched light rare earth element (LREE) patterns ([La/Yb]N = 2.9–3.4; [La/Gd]N = 2.1–2.9) with variable negative Nb anomalies ([Nb/La]N = 0.18–0.81), indicating their dual or hybrid geochemical characteristics. We suggest that their parental magmas may have been generated by the interaction of upwelling asthenospheric and metasomatized lithospheric mantle. Taking into account the spatial and temporal distribution of the Meso

Rapid Mesozoic–Early Cenozoic crustal growth in the Gangdese area, southern Tibet, has commonly been, attributed to pre-collisional and syn-collisional underplating of mantle-derived magmas. Here, we report on, adakitic magnesian charnockites (i.e., hypersthene-bearing diorites and granodiorites) near Milin, in eastern, Gangdese, that provide new insights into the crustal growth process of the region. Zircon U–Pb analyses of' seven charnockite samples indicate that they were generated in the Late Cretaceous (100–89 Ma). They exhibit variable SiO2 (53.9 to 65.7 wt.%) contents, high Na2O/K2O (1.6 to 14.4) and Sr/Y (27.2 to 138.7) ratios, low Y (6.5 to 18.5 ppm), heavy rare earth element (e.g., Yb = 0.6 to 1.6 ppm) and Th (0.20–2.39 ppm) contents and Th/La (0.02–0.23) ratios, with relatively high Mg# (46 to 56) and MgO (2.0 to 4.5 wt.%) values. They are characterized isotopically by high and slightly variable εNd(t) (+ 2.4 to + 4.0) and εHf(t) (+ 10.1 to + 15.8) values with relatively low and consistent (87Sr/86Sr)i (0.7042 to 0.7043) ratios.Their pyroxenes have high crystallization temperatures (876 to 949 °C). The Milin charnockites were most probably produced by partial melting of subducted Neo-Tethyan oceanic crust that was followed by adakitic melt–mantle interaction, minor crustal assimilation and fractional crystallization of amphibole + plagioclase. The upwelling asthenosphere, triggered by the roll-back of subducted Neo-Tethyan oceanic lithosphere, provided the heat for slab melting. Therefore, we suggest that, in addition to pre-collisional and syn-collisional underplating of mantle-derived magmas, the recycling of subducted oceanic crust has also played an important role in continental crustal growth in southern Tibet.

Stimulus-responsive shape-memory materials have attracted tremendous research interests recently, with much effort focused on improving their mechanical actuation. Driven by the needs of nanoelectromechanical devices, materials with large mechanical strain, particularly at nanoscale level, are therefore desired. Here we report on the discovery of a large shape-memory effect in bismuth ferrite at the nanoscale. A maximum strain of up to ∼14% and a large volumetric work density of ∼600±90Jcm-3 can be achieved in association with a martensitic-like phase transformation. With a single step, control of the phase transformation by thermal activation or electric field has been reversibly achieved without the assistance of external recovery stress. Although aspects such as hysteresis, microcracking and so on have to be taken into consideration for real devices, the large shape-memory effect in this oxide surpasses most alloys and, therefore, demonstrates itself as an extraordinary material for potential use in state-of-art nanosystems.

This paper reports on a rare magmatic suite of adakitic rocks and associated magnesian and potassium-rich magmatic enclaves and dikes, which occur in the Tunchang–Fengmu area, Hainan Island (Southeast China). LA-ICP-MS zircon U–Pb age data show that they were generated in the late Early Cretaceous (~107 Ma). The adakitic rocks, consisting mainly of granodiorites and biotite granites, are high-K calcalkaline and have low Mg# values (0.27–0.50). They are geochemically similar to slab-derived adakites, e.g., with high SiO2, Al2O3, Sr, Sr/Y and La/Yb values, low Y and Yb contents, and negligible Eu and positive Sr anomalies. They also have relatively uniform (87Sr/86Sr)i (0.7086–0.7096), (206Pb/204Pb)i (18.50–18.61), (207Pb/204Pb)i (15.56–15.64) and (208Pb/204Pb)i (38.17–38.44) isotope ratios, with slightly variable εNd(t) (-3.85 to -6.55) and zircon in situ εHf(t) (-4.7 to +1.7) values. The mafic enclaves and dikes display disequilibrium textures (e.g., multiple-zoned clinopyroxene with low-MgO rims in contact with perthite and quartz microcrystals). They are high-K calc-alkaline and shoshonitic, and all but one sample have high Mg# (0.63–0.72) values. These mafic rocks are characterized by light rare earth element enrichment and heavy rare earth element (REE) depletion, negligible Eu and Sr and positive Pb anomalies, and Nb and Ta depletion. They have slightly more variable initial 87Sr/86Sr isotope ratios (0.7064–0.7086), εNd(t) (-5.1 to +0.1) values, and (206Pb/204Pb)i (18.35–18.50), (207Pb/204Pb)i (15.45–15.59) and (208Pb/204Pb)i (38.18–38.70) ratios.One mafic dike sample has zircon in situ εHf(t) values (-4.94 to -2.42) similar to those of adakitic rocks (-4.7 to +1.7) in the area. We suggest that the adakitic rocks were most likely generated by partial melting of newly underplated basaltic lower crust with arc-like geochemical characteristics, and the primitive compositions of the mafic enclaves and dikes likely originated from lithospheric + asthenospheric mantl

SIGMOD 2008 was the first database conference that offered to test submitters' programs against their data to verify the repeatability of the experiments published. Given the positive feedback concerning the SIGMOD 2008 repeatability initiative, SIGMOD 2009 modified and expanded the initiative with a workability assessment.

SIGMOD 2008 was the first database conference that offered to test submitters' programs against their data to verify the repeatability of the experiments published. Given the positive feedback concerning the SIGMOD 2008 repeatability initiative, SIGMOD 2009 modified and expanded the initiative with a workability assessment.

In order to efficiently support a large number of on-line analytical processing (OLAP) queries, a data warehouse needs to precompute or materialise some of such OLAP queries. One of the important issues is how to select such a set of materialised views in order to minimise the total processing cost,for OLAP queries. The maintenance-cost view-selection problem is to select a set of materialised views under a maintenance cost constraint (such as maintenance time), in order to minimise the total query processing cost for a given set of queries. This problem is more difficult than the view selection problem under a disk-space constraint, because a selected view may make the previously selected views less beneficial, due to the fact that the total maintenance cost for a set of views may decrease when more views are materialised while the maintenance cost always increases under disk-space constraint. The problem has recently received significant attention. Several greedy/heuristic algorithms were proposed. However the quality of the greedy/heuristic algorithms has not been well analysed. In this paper, in a multidimensional data warehouse environment, we re-examine the greedy/heuristic algorithms in various settings, and provide users with insights on the quality of these heuristic algorithms.

In order to efficiently support a large number of on-line analytical processing (OLAP) queries, a data warehouse needs to precompute or materialise some of such OLAP queries. One of the important issues is how to select such a set of materialised views in order to minimise the total processing cost,for OLAP queries. The maintenance-cost view-selection problem is to select a set of materialised views under a maintenance cost constraint (such as maintenance time), in order to minimise the total query processing cost for a given set of queries. This problem is more difficult than the view selection problem under a disk-space constraint, because a selected view may make the previously selected views less beneficial, due to the fact that the total maintenance cost for a set of views may decrease when more views are materialised while the maintenance cost always increases under disk-space constraint. The problem has recently received significant attention. Several greedy/heuristic algorithms were proposed. However the quality of the greedy/heuristic algorithms has not been well analysed. In this paper, in a multidimensional data warehouse environment, we re-examine the greedy/heuristic algorithms in various settings, and provide users with insights on the quality of these heuristic algorithms.

In order to efficiently support a large number of on-line analytical processing (OLAP) queries, a data warehouse needs to precompute or materialise some of such OLAP queries. One of the important issues is how to select such a set of materialised views in order to minimise the total processing cost,for OLAP queries. The maintenance-cost view-selection problem is to select a set of materialised views under a maintenance cost constraint (such as maintenance time), in order to minimise the total query processing cost for a given set of queries. This problem is more difficult than the view selection problem under a disk-space constraint, because a selected view may make the previously selected views less beneficial, due to the fact that the total maintenance cost for a set of views may decrease when more views are materialised while the maintenance cost always increases under disk-space constraint. The problem has recently received significant attention. Several greedy/heuristic algorithms were proposed. However the quality of the greedy/heuristic algorithms has not been well analysed. In this paper, in a multidimensional data warehouse environment, we re-examine the greedy/heuristic algorithms in various settings, and provide users with insights on the quality of these heuristic algorithms.