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1.
HAN Ke YANG Xingke CHAO Huixi HE Hujun RUAN Shiqi GAO Yunfeng ZHANG Weisheng ZHU Wei JIN Gang 《《地质学报》英文版》2021,95(2):500-516
A W-Mo mineralized region is located along the northern margin of the South Qinling tectonic belt of China. WMo mineralization occurs mainly in Cambrian–Ordovician clastic and carbonate rocks, and the ore bodies are structurally controlled by NW–SE-and NNE–SSW-striking faults. Evidence for magmatism in the area is widespread and is dominated by intermediate–felsic intrusives or apophyses, such as the Dongjiangkou, Yanzhiba, Lanbandeng, and Sihaiping granitic bodies. Quartz-vein-type mineralization and fault-controlled skarn-type mineralization dominate the ore systems, with additional enrichment in residual deposits. At present, there are few or insufficient studies on(1) the age of mineralization,(2) the relationship between intermediate–felsic granite and W-Mo mineralization,(3) the source of ore-forming materials,and(4) the metallogenic and tectonic setting of the mineralized area. In this paper, we present geochronology results for numerous intrusive granitic bodies in the South Qinling tectonic belt. U-Pb zircon geochronology of the Lanbandeng monzogranite and Wangjiaping biotite monzogranite yields ages of 222.7 ± 2.3 and 201.9 ± 1.8 Ma, respectively. In contrast to the Late Triassic age of the Lanbandeng monzogranite, the age of the newly discovered Wangjiaping biotite monzogranite places it at the Triassic–Jurassic boundary. Re-Os molybdenite geochronology on the Qipangou W-Mo deposit yielded a model age of 199.7 ± 3.9 Ma, indicating the deposit formed in the early Yanshanian period of the Early Jurassic. Granitoid intrusions in the mineralized area are characterized by composite granite bodies that crystallized at ca.240–190 Ma. While there were multiple stages of intrusion, most occurred at 210–220 Ma, with waning magmatic activity at 200–190 Ma. The Re-Os age of molybdenite in the region is ca. 200–190 Ma, which may represent a newly discovered period of W-Mo metallogenesis that occurred during the final stages of magmatism. The heat associated with this magmatism drove ore formation and might have provided additional ore-forming components for metallogenesis(represented by the Wangjiaping biotite monzogranite). Ore materials in the mineralized area were derived from mixed crustal and mantle sources. Enrichment of the region occurred during intracontinental orogenesis in the late Indosinian–Yanshanian, subsequent to the main Indosinian collision. At this time, the tectonic environment was dominated by extension and strike-slip motion. 相似文献
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1931年,Mehl报道的来自Dakota Group的Ignotornis mcconnelli是第一个被广泛接受的中生代鸟类足迹。目前,亚洲、北美洲、欧洲、非洲和南美洲都有白垩纪鸟类足迹的报道,尤其以东亚地区最为丰富。山东诸城张祝河湾恐龙足迹点保存了一枚完整的鸟类足迹,本文对该鸟类足迹进行了详细描述与对比。研究认为,该鸟类足迹区别于以往发现的鸟类足迹,根据其形态建立了新种:玲珑诸城鸟足迹Zhuchengornipes exquisitus。玲珑诸城鸟足迹造迹者可能为滨鸟类,形成于干旱气候下的滨浅湖环境。 相似文献
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本文选择大兴安岭北段诺敏大山地区早白垩世侵入岩进行了锆石U-Pb年代学和地球化学研究,探讨该区域侵入岩成因类型、岩浆来源及构造环境。该区侵入岩岩性主要为正长花岗岩、正长花岗斑岩和似斑状正长花岗岩,对其中正长花岗岩样品进行LA-ICP-MS锆石U-Pb测年表明,正长花岗岩侵位年龄为129.5±0.4 Ma,应为早白垩世岩浆活动的产物,结合区内侵入岩与地层相互接触关系,本区侵入岩形成时代为早白垩世。区内侵入岩具有富硅(SiO2= 67.36%~74.09%)、富碱(K2O+Na2O= 8.88%~9.34%)、高铝(Al2O3= 12.56%~16.15%),低MgO、TiO2、CaO的特点,属于高钾钙碱性岩石系列;铝饱和指数(A/CNK)为0.94~1.31,为准铝质—过铝质岩石。微量元素富集Rb、U、Th、K等大离子亲石元素,强烈亏损Ti、Nb、Sr、P等高场强元素,具有明显的Eu负异常,属于高分异I型花岗岩。岩石Rb/Sr为0.9~2.0,Sr/Y为4.2~7.2,显示出高Sr、低Y的特点,指示岩浆源区为地壳物质的部分熔融。结合区域研究成果,蒙古—鄂霍茨克构造域在早白垩世之前已结束碰撞,诺敏大山地区早白垩世岩浆活动可能发生在蒙古—鄂霍茨克造山后的伸展环境。 相似文献
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川东南—黔北地区下志留统龙马溪组发育富含有机质泥页岩,是华南地区海相地层中的优质烃源岩之一,且分布广泛,厚度大,是有利的页岩气勘探区。通过研究区30条野外露头剖面和12口钻井的资料分析,结合岩性、元素地球化学、测井地球物理及古生物等相标志研究,对川东南—黔北地区下志留统龙马溪组沉积环境、沉积演化及其对烃源岩的影响进行了研究,在川东南—黔北地区龙马溪组识别出泥质深水陆棚、泥质浅水陆棚、砂泥质浅水陆棚、砂质浅水陆棚、灰泥质浅水陆棚、灰质浅水陆棚、浊流沉积、台地边缘浅滩-生物礁浊流等8种沉积类型,其中泥质深水陆棚是龙马溪组烃源岩形成的主要沉积环境。通过对沉积环境的研究,认为龙马溪组底部缺氧的滞留环境和缓慢的沉积速率是龙马溪组优质烃源岩发育的主要因素。研究为区内页岩气勘探开发提供有力保障。 相似文献
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基于腹地划分的中国城市群空间影响范围识别 总被引:6,自引:0,他引:6
城市群空间影响范围的界定是认清城市群内中心城市与腹地、城市与城市间相互关联的基础。采用主成分分析法计算中国287个地级及以上城市的结节性指数,利用累积耗费距离法和k阶数据场,综合测度了交通可达性与空间场能,根据场强"取大"原则对城市腹地进行了划分,依据城市腹地范围界定了城市群的空间影响范围。结果表明:①中国地级以上城市最大和最小结节性指数相差157.53倍,城市平均可达时间为193.43 min,场能平均值为5 412,最大和最小城市腹地相差3 751倍;②23个城市群中,空间影响范围最大的是北疆城市群,空间平均场强最大的是中原城市群;③城市群在空间上呈现为发育程度不同的"11+9+3"的分布格局和逆时针90°旋转的"β"型城市群连绵带发展格局;④基于腹地划分的城市群空间影响范围充分考虑了现实的交通网络和地形地貌特点,实现了对广域空间范围内城市腹地范围和城市群空间影响范围的定量测度。 相似文献
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基于相关分析和自适应遗传算法的盐渍化建模变量和参数优选 总被引:1,自引:0,他引:1
机器学习结合遥感等其他数据反演土壤盐分含量(Soil Salt Content, SSC)较少关注对模型精度影响较大的建模特征变量和模型参数的优选。本文基于自适应遗传算法(Adaptive Genetic Algorithm, AGA)同步优选建模特征变量和模型参数的支持向量回归(Support Vector Regression, SVR)算法反演三工河流域2016年SSC,并分析其在不同土地利用类型的分布特征。建模特征变量和模型参数的同步优选及实验设计如下:首先基于Landsat 8 OLI和SRTM高程数据提取7类共40个盐渍化相关因子,经相关分析初步筛选出候选特征变量,分别代入AGA、遗传算法(Genetic Algorithm, GA)和格网搜索算法(Grid Search, GS)同步优选SVR的建模特征变量和模型参数,并建立盐渍化监测模型(AGA-SVR、GA-SVR、GS-SVR)。结果表明:① AGA-SVR精度最优,GA-SVR次之,GS-SVR最差,相较于GS-SVR,AGA-SVR的R2/RMSE提高了44.65%;② 三工河流域非、轻度、中度、重度盐渍地和盐土的面积占比分别为42.83%、11.02%、15.88%、9.22%、21.05%;③ 草地和未利用地主要以非盐渍地和盐土为主,耕地和林地中非盐渍地分布比例均为最大;不同土地利用类型的SSC均值和标准差均呈现未利用地>草地>耕地>林地的规律。本研究的建模特征变量和模型参数的优选方法可在一定程度上提高盐渍化监测的精度。关键词:盐渍化;遗传算法;机器学习;特征优选;参数优化;土壤盐分含量;土地利用;相关分析 相似文献
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Hongyan Geng Min Sun Chao Yuan Wenjiao Xiao Weisheng Xian Guochun Zhao Lifei Zhang Kenny Wong Fuyuan Wu 《Chemical Geology》2009,266(3-4):373-398
Voluminous granitic intrusions are distributed in the West Junggar, NW China, and they can be classified as the dioritic rocks, charnockite and alkali-feldspar granite groups. The dioritic rocks (SiO2 = 50.4–63.8 wt.%) are calc-alkaline and Mg enriched (average MgO = 4.54 wt.%, Mg# = 0.39–0.64), with high Sr/Y ratios (average = 21.2), weak negative Eu (average Eu/Eu = 0.80) and pronounced negative Nb–Ta anomalies. Their Sr–Nd and zircon Hf isotopic compositions ((87Sr/86Sr)i = 0.7035–0.7042, εNd(t) = 4.5–7.9, εHf(t) = 14.1–14.5) show a depleted mantle-like signature. These features are compatible with adakites derived from partial melting of subducted oceanic crust that interacted with mantle materials. The charnockites (SiO2 = 60.0–65.3 wt.%) show transitional geochemical characteristics from calc-alkaline to alkaline, with weak negative Eu (average Eu/Eu = 0.75) but pronounced negative Nb–Ta anomalies. Sr–Nd and zircon Hf isotopic compositions ((87Sr/86Sr)i = 0.7037–0.7039, εNd(t) = 5.2–8.0, εHf(t) = 13.9–14.7) also indicate a depleted source, suggesting melts from a hot, juvenile lower crust. Alkali-feldspar granites (SiO2 = 70.0–78.4 wt.%) are alkali and Fe-enriched, and have distinct negative Eu and Nb–Ta anomalies (average Eu/Eu = 0.26), low Sr/Y ratios (average = 2.11), and depleted Sr–Nd and zircon Hf isotopic compositions ((87Sr/86Sr)i = 0.7024–0.7045, εNd(t) = 5.1–8.9, εHf(t) = 13.7–14.2). These characteristics are also comparable with those of rocks derived from juvenile lower crust. Despite of the differences in petrology, geochemistry and possibly different origins, zircon ages indicate that these three groups of rocks were coevally emplaced at ~ 305 Ma.A ridge subduction model can account for the geochemical characteristics of these granitoids and coeval mafic rocks. As the “slab window” opened, upwelling asthenosphere provided enhanced heat flux and triggered voluminous magmatisms: partial melting of the subducting slab formed the dioritic rocks; partial melting of the hot juvenile lower crust produced charnockite and alkali-feldspar granite, and partial melting in the mantle wedge generated mafic rocks in the region. These results suggest that subduction was ongoing in the Late Carboniferous and, thus support that the accretion and collision in the Central Asian Orogenic Belt took place in North Xinjiang after 305 Ma, and possibly in the Permian. 相似文献