Neoproterozoic adakitic plutons and arc magmatism along the western margin of the Yangtze Block, South China

Neoproterozoic adakitic plutons that crop out along the western margin of the Yangtze Block (South China) from Kangding on the north to Panxi on the south provide constraints on the origin of the giant Jinningian magmatic event of South China. Representative plutons include the Xuelongbao (750 Ma), Datian (760 Ma), and Dajianshan intrusions. The latter two bodies consist mainly of granodiorite with relatively high SiO2 (51.0-73.4 wt%) and Mg#'s (0.36-0.55). They have fractionated rare earth element patterns, with (La/Yb)N ratios ranging from 2.6 to 101.8, and are characterized by high Sr (344-1018 ppm) and low Y (4.3-17.9 ppm), yielding Sr/Y ratios ranging from 27 to 111. On primitive mantle-normalized trace-element diagrams, these rocks show enrichment of large-ion lithophile elements and depletion of high-field-strength elements (Nb, Ta), with positive Zr-Hf and negative Ti anomalies, consistent with an arc-related setting. They have relatively constant initial whole-rock 87Sr/86Sr ratios (0.704308-0.705068) and εNd values (+0.66 to -0.92). From their geochemistry, these plutons are interpreted to have formed in an arc environment. The parental magmas were generated from partial melts of a subducted oceanic slab that were modified by interaction with the overlying mantle wedge. Therefore, we conclude that the western margin of the Yangtze Block was an active magmatic arc during the Neoproterozoic. © 2007 by The University of Chicago. All rights reserved.published_or_final_versio

Melting of newly formed mafic crust for the formation of Neoproterozoic I-type granite in the Hannan region, South China

Neoproterozoic magmatism in the Hannan region at the northwestern margin of the Yangtze Block is characterized by numerous felsic plutons associated with minor mafic-ultramafic intrusions. The felsic plutons are either adakitic or normal-arc granitic in composition. The adakitic plutons are ∼735 Ma in age and are interpreted as having formed by partial melting of a thickened lower mafic crust. Among the normal-arc-related felsic plutons, the Tianpinghe pluton is the largest and has a SHRIMP zircon U-Pb age of 762 ± 4 Ma, older than the adakitic plutons in the region. Rocks from the Tianpinghe pluton have relatively high SiO2 (67.1-70.1 wt%) and K2O+ Na 2O (7.8-8.6 wt%) and relatively low MgO (0.7-1.3 wt%) and Al 2O3 contents (14.5-15.6 wt%), with Al2O 3/(CaO + K2O + Na2O) (A/CNK) values ranging from 0.95 to 1.08. They have arc-affinity trace-element compositions that are characterized by enrichment of large-ion lithophile elements and depletion of high-field-strength elements (Nb, Ta), with strong positive Pb and negative Ti anomalies. They have a narrow range of εNd(t) values (+0.15 to - 1.76) and relatively high zircon eHf values (+0.6 to - 8.3). These geochemical features are typical of I-type granites. The rocks from the Tianpinghe pluton have relatively young single-stage and two-stage Hf model ages (1.01-1.31 and 1.31-2.01 Ga, respectively), suggesting that the pluton was generated by partial melting of newly formed basaltic rocks. On the basis of its arc-related geochemical affinity and its emplacement before voluminous adakitic magmatism but after mafic-ultramafic intrusions, the Tianpinghe pluton is considered to be Neoproterozoic arc granite formed during a period of crustal growth and reworking. Generation of the later adakitic plutons suggests that the crustal thickness increased to more than 50 km by mafic magma underplating. © 2009 by The University of Chicago. All rights reserved.published_or_final_versio

Geochronology and geochemistry of the c. 80 Ma Rutog granitic pluton, northwestern Tibet: Implications for the tectonic evolution of the Lhasa Terrane

The Rutog granitic pluton lies in the Gangdese magmatic arc in the westernmost part of the Lhasa Terrane, NW Tibet, and has SHRIMP zircon U-Pb ages of c. 80 Ma. The pluton consists of granodiorite and monzogranite with SiO2 ranging from 62 to 72 wt% and Al2 O3 from 15 to 17 wt%. The rocks contain 2.33-4.93 wt% K2O and 3.42-5.52 wt% Na2O and have Na2O/K2O ratios of 0.74-2.00. Their chondrite-normalized rare earth element (REE) patterns are enriched in LREE ((La/Yb)n = 15 to 26) and do not show significant Eu anomalies (αEu = 0.68-1.15). On a primitive mantle-normalized trace element diagram, the rocks are rich in large ion lithophile elements (LILE) and poor in high field strength elements (HFSE), HREE and Y. Their Sr/Y ratios range from 15 to 78 with an average of 30. The rocks have constant initial 87Sr/86Sr ratios (0.7045 to 0.7049) and slightly positive εNd(t) values (+0.1 to +2.3), similar to I-type granites generated in an arc setting. The geochemistry of the Rutog pluton is best explained by partial melting of a thickened continental crust, triggered by underplating of basaltic magmas in a mantle wedge. The formation of the Rutog pluton suggests flat subduction of the Neo-Tethyan oceanic lithosphere from the south. Crustal thickening may have occurred in the Late Cretaceous prior to the India-Asia collision. © Cambridge University Press 2008.published_or_final_versio

The characteristics of automobile catalyst-derived platinum group elements in road dusts and roadside soils: A case study in the Pearl River Delta region, South China

The emission of platinum group elements (PGE) from automobile catalytic converters has led to enrichment of PGE in road dusts and roadside soils in urban areas that are well above the natural background levels. This paper evaluates the source of contamination of all the PGE and Au in road dusts and roadside soils in the Pearl River Delta region, including three major cities, Shenzhen, Guangzhou and Hong Kong, South China. Samples were digested using Carius tube and analyzed by isotope dilution ICP-MS; Os was separated by distillation and other PGE by Te-coprecipitation. All samples have elevated PGE concentrations above the background values of uncontaminated soils and contain higher Pt, Pd and Rh than other PGE. The maximum values are 181 ng/g Pt, 514 ng/g Pd, 53 ng/g Rh and 1345 ng/g Au. There are clear positive correlations between Pt and Pd, Pt and Rh, and Pd and Rh, indicating that the main emitted of PGE from automobile catalyst are Pt, Pd and Rh. High concentrations of Au were also found in road dust samples from Hong Kong and Shenzhen. Dust samples with higher Os contents have lower 187Os/ 188Os ratios. Samples from Hong Kong show relatively high Pt/Rh ratios. Positive correlations between Pt and Ru, and Pt and Ir were found in Shenzhen and Hong Kong, but only positive correlations between Pt and Ir were found in Guangzhou. These different characteristics reflect different automobile catalytic systems used in Hong Kong and mainland China. © 2010 The Author(s).published_or_final_versionSpringer Open Choice, 21 Feb 201

Neoproterozoic Mafic-Ultramafic Intrusions from the Fanjingshan Region, South China: Implications for Subduction-Related Magmatism in the Jiangnan Fold Belt

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Elemental and Sr-Nd-Pb isotopic geochemistry of Mesozoic mafic intrusions in southern Fujian Province, SE China: Implications for lithospheric mantle evolution

Abstract Cretaceous mafic dykes in Fujian province, SE China provide an opportunity to examine the nature of their mantle source and the secular evolution of the Mesozoic lithospheric mantle beneath SE China. The mafic rocks have SiO2 ranging from 47.42 to 55.40 wt %, Al2O3 from 14.0 wt % to 20.4 wt %, CaO from 4.09 to 11.7 wt % and total alkaline (K2O+Na2O) from 2.15 wt % to 6.59 wt %. Two types are recognized based on their REE and primitive mantle-normalized trace element patterns. Type-A is the dominant Mesozoic mafic rock type in SE China and is characterized by enrichment of light rare earth elements (LREE) ((La/Yb)n = 2.85-19.0) and arc-like trace element geochemistry. Type-P has relatively flat REE patterns ((La/Yb)n = 1.68-3.43) and primitive mantle-like trace element patterns except for enrichment of Rb, Ba and Pb. Type-A samples show EMII signatures on the Sr-Nd isotopic diagram, whereas type-P rocks have high initial 143Nd/144Nd ratios (0.5126-0.5128) relative to the type-A rocks (143Nd/144Nd = 0.5124-0.5127). The type-A rocks have 207Pb/204Pb ranging from 15.47 to 15.67 and 206Pb/204Pb from 18.26 to 18.52. All the type-A rocks show a negative correlation between 143Nd/144Nd and 206Pb/204Pb ratios and a positive relationship between 87Sr/86 Sr and206Pb/204Pb ratios, indicating mixing of a depleted mantle source and an EMII component. Geochemical modelling shows that the parental magmas were formed by 5-15 % partial melting of a spinel lherzolite, and contaminated by less than 1 % melt derived from subducted sediment. The type-P magmas were derived from a mantle source unmodified by subduction components. The wide distribution of type-A dykes in SE China suggests that subduction-modified lithospheric mantle was extensive beneath the Cathaysia Block. Geochemical differences between Mesozoic and Cenozoic mafic rocks indicate that lithospheric thinning beneath SE China occurred in two episodes: firstly by heterogeneous modification by subducted components in early Mesozoic times, and later by chemical-mechanical erosion related to convective upwelling of the asthenosphere during Cenozoic times. © 2007 Cambridge University Press.published_or_final_versio

Heterogeneous mantle source and magma differentiation of quaternary arc-like volcanic rocks from Tengchong, SE margin of the Tibetan Plateau

The Tengchong volcanic field north of the Burma arc comprises numerous Quaternary volcanoes in the southeastern margin of the Tibetan Plateau. The volcanic rocks are grouped into four units (1-4) from the oldest to youngest. Units 1, 3 and 4 are composed of olivine trachybasalt, basaltic trachyandesite and trachyandesite, and Unit 2 consists of hornblende dacite. The rocks of Units 1, 3, and 4 form a generally alkaline suite in which the rocks plot along generally linear trends on Harker diagrams with only slight offset from unit to unit. They contain olivine phenocrysts with Fo values ranging from 65 to 85 mol% and have Cr-spinel with Cr# ranging from 23 to 35. All the rocks have chondrite-normalized REE patterns enriched in LREE and primitive mantle-normalized trace element patterns depleted in Ti, Nb and Ta, but they are rich in Th, Ti and P relative to typical arc volcanics. Despite minor crustal contamination, 87Sr/ 86Sr ratios (0.706-0.709), εNd values (-3.2 to -8.7), and εHf values (+4.8 to -6.4) indicate a highly heterogeneous mantle source. The Pb isotopic ratios of the lavas ( 206Pb/ 204Pb = 18.02-18.30) clearly show an EMI-type mantle source. The underlying mantle source was previously modified by subduction of the Neo-Tethyan oceanic and Indian continental lithosphere. The present heterogeneous mantle source is interpreted to have formed by variable additions of fluids and sediments derived from the subducted Indian Oceanic lithosphere, probably the Ninety East Ridge. Magma generation and emplacement was facilitated by transtensional NS-trending strike-slip faulting. © 2011 The Author(s).published_or_final_versionSpringer Open Choice, 28 May 201

Cluster Based Term Weighting Model for Web Document Clustering

The term weight is based on the frequency with which the term appears in that document. The term weighting scheme measures the importance of a term with respect to a document and a collection. A term with higher weight is more important than a term with lower weight. A document ranking model uses these term weights to find the rank of a document in a collection. We propose a cluster-based term weighting models based on the TF-IDF model. This term weighting model update the inter-cluster and intra-cluster frequency components uses the generated clusters as a reference in improving the retrieved relevant documents. These inter cluster and intra-cluster frequency components are used for weighting the importance of a term in addition to the term and document frequency components

Geospatial information infrastructures

Manual of Digital Earth / Editors: Huadong Guo, Michael F. Goodchild, Alessandro Annoni .- Springer, 2020 .- ISBN: 978-981-32-9915-3Geospatial information infrastructures (GIIs) provide the technological, semantic,organizationalandlegalstructurethatallowforthediscovery,sharing,and use of geospatial information (GI). In this chapter, we introduce the overall concept and surrounding notions such as geographic information systems (GIS) and spatial datainfrastructures(SDI).WeoutlinethehistoryofGIIsintermsoftheorganizational andtechnologicaldevelopmentsaswellasthecurrentstate-of-art,andreflectonsome of the central challenges and possible future trajectories. We focus on the tension betweenincreasedneedsforstandardizationandtheever-acceleratingtechnological changes. We conclude that GIIs evolved as a strong underpinning contribution to implementation of the Digital Earth vision. In the future, these infrastructures are challengedtobecomeflexibleandrobustenoughtoabsorbandembracetechnological transformationsandtheaccompanyingsocietalandorganizationalimplications.With this contribution, we present the reader a comprehensive overview of the field and a solid basis for reflections about future developments