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

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

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

Quantifying Model Complexity via Functional Decomposition for Better Post-Hoc Interpretability

Post-hoc model-agnostic interpretation methods such as partial dependence plots can be employed to interpret complex machine learning models. While these interpretation methods can be applied regardless of model complexity, they can produce misleading and verbose results if the model is too complex, especially w.r.t. feature interactions. To quantify the complexity of arbitrary machine learning models, we propose model-agnostic complexity measures based on functional decomposition: number of features used, interaction strength and main effect complexity. We show that post-hoc interpretation of models that minimize the three measures is more reliable and compact. Furthermore, we demonstrate the application of these measures in a multi-objective optimization approach which simultaneously minimizes loss and complexity

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

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

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华北克拉通北缘晚中生代火山岩Sr-Nd-Pb同位素填图及其构造意义

辽宁西部广泛分布着晚中生代火山岩，横跨华北克拉通和兴> 蒙造山带两大构造单元，一般认为它们是以在这一地区发育的两条主要断裂———西拉木伦河断裂和赤峰> 开源断裂为界。这些火山作用曾被认为是中生代伊泽奈崎板块西向或西北向消减作用的结果。在岩性上它们主要以中酸性岩石为主，玄武岩等中基性岩石较少。为查明下伏岩石圈对这些岩浆作用成因的影响，对其中的SiO2 含量 开源断裂两侧为界，两侧火山岩的同位素特征存在显著区别。南区有明显的EMI 特征并具EMI-PM 混合趋势，而北区则显示了原始或略亏损的特征。南北两区之间的过渡带（介于西拉木伦河断裂和赤峰> 开源断裂之间）则表现了同位素组成上相应的过渡特征。这一地球化学观测与已有的地质和地球物理资料颇为吻合。基于新生代幔源岩石化学反演的中国东部陆下地幔化学区划研究揭示了克拉通下(subcratonic)岩石圈地幔与EMI 存在着密切关系。本研究所提供的地球化学证据说明了采用中生代中基性岩类作为类似研究途径的可行性，并进一步提出对华北克拉通边缘中生代火山作用成因另一种可能的解释，即古消减带物质的活化有可能对华北北缘火山岩源区物质组成产生重要影响。Late Mesozoic volcanic rocks are extensively spread on both sides of northern margin of the North China Craton (NCC), where is the boundary between an Archean craton to the south and a Paleozoic orogenic belt, Xing an- Mongolia Orogenic Belt (XMOB), to the north. Two major east- west trending faults, Kaiyuan- Chifeng Fault (KCF) and Xar Moron He Fault (XHF) develop in this margin zone as a boundary between two tectonic domains. The volcanism has been thought to be the magmatic response to the west- , or no...published_or_final_versio

Ethanol extract of Hedyotis diffusa willd. induction of apoptosis via PI3K/Akt and XIAP pathways in human leukemic THP-1 cells

Hedyotis diffusa (H. diffusa) Willd. is known to induce apoptosis in cancer cells. However, the molecular mechanism of its anti-cancer activity has not been fully elucidated. In this study, we found that the ethanol extract of H. diffusa Willd. (EEHDW) reduced cell viability and induced apoptosis in a dose- and time-dependent manner in human leukemic THP-1 cells. The induction of apoptosis was also accompanied by the down regulation of PI3K/Akt and the inhibitor of apoptosis protein (IAP) family proteins. Moreover, we observed that EEHDW treatment resulted in activation of caspase-3, which may partly explain the anti-cancer activity of EEHDW.Key words: Hedyotis diffusa Willd., THP-1, apoptosis, caspase

Flux jumps in ring-shaped and assembled bulk superconductors during pulsed field magnetization

Abstract Bulk (RE)BCO, where RE is a rare-earth element or yttrium, superconductors fabricated in the form of rings are potentially useful for a variety of solenoidal-type applications, such as small, high field nuclear magnetic resonance and electromagnetic undulators. It is anticipated that the practical exploitation of these technologically important materials will involve pulse field magnetization (PFM) and, consequently, it is important to understand the behavior of ring-shaped samples subjected to the PFM process. Macroscopic flux jumps were observed in PFM experiments on ring-shaped bulk samples when the peak applied field reaches a threshold magnitude, similar to behavior reported previously in cylindrical samples. Magnetic flux jumps inward when the thermal instability is triggered, however it subsequently flows outwards from the sample, resulting in a relatively low trapped field. This behavior is attributed to a variety of effects, including the inhomogeneity of the material, which may lead to the formation of localized hot spots during the PFM process. In order to further elucidate this phenomena, the properties of a structure consisting of a bulk superconducting ring with a cylindrical superconductor core were studied. We observe that, although a flux jump occurs consistently in the ring, a critical state is established at the boundary of the ring-shaped sample and the core. We provide a detailed account of these experimental observations and provide an explanation in terms of the current understanding of the PFM process.This work was supported by the Engineering and Physical Sciences Research Council (grant number: EP/P00962X/1) and the State Key Laboratory of Traction Power at Southwest Jiaotong University (TPL-1709)