Kuiper带天体的原始分布模拟

用包括太阳、8颗大行星、冥王星和UB313以及无质量实验粒子在内的N体问题的天体动力学模型,取当前观测的天体轨道根数为初始条件,对具有确定轨道根数的551个Kuiper主带内的小天体进行了10亿年的轨道反演数值模拟.结果显示:当前观测的这些Kuiper 天体中的1/3以上在10亿年前就位于该区域,少部分位于海王星轨道之内,其他在5OAU之外;在4.5亿年前,整个Kuiper主带内的天体呈较好的正态分布,海王星3:2共振带内没有像今天这样的天体聚集现象.     

李希霍芬的中国考察及其当代人文-经济地理学价值刍议

德国著名的地质学家和地理学家李希霍芬关于中国的研究成果打开了近代西方国家认识和了解中国的窗口,他命名的“丝绸之路”得到中外学者的广泛认同并沿用至今。国内学界对李希霍芬学术贡献的评述聚焦于他对中国地质和地球科学的贡献，但对其研究成果的人文-经济地理学价值尚缺少深入的总结。本文分析李希霍芬到中国考察的国内外政治经济和文化背景，以《李希霍芬中国旅行日记》为基础文献，梳理李希霍芬于1868~1872年间在中国的历次考察路线和主要考察内容，以及与中国古“丝绸之路”相关的考察计划；从当代人文-经济地理学视角总结分析了李希霍芬对中国研究的学术价值和贡献，如区位分析、“联系”与“流”的分析、农业地域差异分析、人地关系分析、制度与文化因素分析等；最后提出李希霍芬在中国的考察研究对当今“一带一路”建设研究及人文-经济地理学界的启示。     

“一带一路”背景下中欧港口航运网络的演化特征

中国与欧洲位于欧亚大陆的东西两端,中欧的贸易畅通是“一带一路”发展的重要内容。当前,中欧经贸联系仍主要通过海运完成,中欧港口航运网络的连通是贸易畅通的保障,因此,研究中欧港口航运网络的发展演变对于认识和保障中欧贸易的畅通具有重要意义。依据近20 a的3个时间断面(1995、2005、2015年）航运数据,构建中国与欧洲各港口航线联系网络,并通过刻画港口航运网络的复杂性特征,揭示不同港口节点可达性变化的空间分异,进而从中转港体系、网络组织结构两方面探讨中欧航运网络的演化特征。研究表明：① 1995年以来,中欧航线联系的港口节点显著增加,网络覆盖范围明显扩大。2005年和2015年网络均表现出明显的小世界特征和无标度特性;不同港口航线联系的广度、深度和可达性变化差异明显,其中84%的港口可达性增强,地中海和阿拉伯海沿岸少数港口可达性减小。② 中欧航运网络的中转港体系由“V”型转变为“U”型,核心中转港出现分化、中转节点逐渐体系化,中转路径趋于多元化,网络稳定性增强。③ 中欧航运网络的轴—辐组织结构不断优化,网络运行效率明显提升,航线联系更加多元化、复杂化。中欧港口航运网络的轴—辐空间结构经历了“三角型”“均衡哑铃型”和“非均衡哑铃型”3个阶段,最终形成以上海港和鹿特丹港为主枢纽的多层次轴—辐空间组织结构。     

In situ monazite (U–Th)–Pb ages from the Southern Brasília Belt,Brazil: constraints on the high‐temperature retrograde evolution of HP granulites

In the southern sector of the Southern Brasília Belt, late Neoproterozoic arc–passive margin collision resulted in juxtaposition of an arc‐derived nappe (the Socorro–Guaxupé Nappe) over a stack of passive margin‐derived nappes (the Andrelândia Nappe Complex) that lies on top of autochthonous basement of the São Francisco Craton. (U–Th)–Pb monazite ages are reported from the high‐grade nappes of the Andrelândia Nappe Complex to better constrain the high‐temperature retrograde evolution. For residual HP granulites from the uppermost Três Pontas–Varginha Nappe, (U–Th)–Pb ages of c. 662 and 655 Ma from low yttrium monazite inclusions in the rims of, or associated with garnet are interpreted to date the late‐stage close‐to‐peak prograde evolution, whereas an age of c. 648 Ma from a similar low yttrium monazite inclusion is interpreted to record post‐peak recrystallization with melt via factures in garnet. For the same nappe, ages of 640–631 Ma retrieved from higher yttrium areas or cores in monazite grains that occur both as inclusions in garnet and in the matrix are interpreted to record growth of monazite either by local breakdown of garnet (±older monazite) and mass exchange with a matrix melt reservoir along cracks or growth from residual melt in the matrix as it crystallized during high‐pressure, close‐to‐isobaric cooling close to the solidus, the temperature of which, at a given pressure, varies with bulk composition of the residual granulites. (U–Th)–Pb ages in the range 620–588 Ma from lower yttrium areas in these monazite grains and from matrix‐hosted patchy monazite are interpreted to date exhumation, as recorded by close‐to‐isothermal decompression and subsequent close‐to‐isobaric cooling. Older monazite ages in this group are interpreted to record late‐stage interaction with melt close to the solidus whereas younger monazite ages are interpreted to record recrystallization of monazite by dissolution–reprecipitation owing to ingress of alkali fluid from the Carmo da Cachoeira Nappe beneath as fluid was released by crystallization of in‐source melt at the solidus. In the underlying Carmo da Cachoeira Nappe, higher yttrium areas in monazite and one single domain monazite yield chemical ages of 619–616 Ma, which are interpreted to date growth as in‐source melt crystallized close to the solidus along the high‐pressure, close‐to‐isobaric segment of the retrograde P–T evolution. Younger (U–Th)–Pb ages of 600–595 Ma retrieved from lower yttrium areas and one single domain monazite are interpreted to record recrystallization of monazite by dissolution–reprecipitation owing to release of fluid at the solidus during exhumation of this nappe. Monazite from the Carvalhos Klippe, interpreted to be correlative with the uppermost nappe, yields a wide range of (U–Th)–Pb ages: for two zoned grains, c. 619 and c. 614 Ma from higher yttrium cores, and c. 583 and c. 595 Ma from lower yttrium rims; and, 592–580 Ma from single domain grains in one sample, and ages of c. 593 and c. 563 Ma from monazite in a second sample. Ages younger than 605 Ma are interpreted to date a fluid‐induced response to the early stages of orogenic loading associated with terrane accretion in the Ribeira Belt to the southeast. The results reported here demonstrate that ages retrieved from monazite that grew close to the solidus in residual granulites from a single tectonic unit will vary from sample to sample according to differences in the solidus temperatures. Further, we show that monazite inclusions may yield ages that are younger than the host mineral and confirm the propensity of monazite to record evidence of tectonic events that are not always registered by other high‐temperature mineral chronometers.     

郯庐断裂带鲁苏沂沭段对汶川地震波的隔震效应

郯庐断裂带鲁苏沂沭段由几务平行的深大断裂构成。地震波传播通过郯庐断裂带会产生多次的反射与折射,适当的条件下会产生断层隔震效应。本文报告了江苏地区在汶川地震中的人员反应,根据弹性波传播理论分析了江苏境内的汶川地震记录。分析结果表明,郯庐断裂带在嘉山以北为郯庐断裂带鲁苏沂沭段,几条平行的深大断裂有隔震效应,汶川与嘉山南侧的连线形成一条地震动屏蔽线。在此线以北,郯庐断裂带鲁苏沂沭段阻碍了地震波的传播,其东侧,紧邻郯庐断裂带并为郯庐断裂带屏蔽的强震观测台如宿迁台、新沂台和淮安台都没有触发,这表明了郯庐断裂带对地震波的隔震作用。     

Late Carboniferous – Middle Permian arc/forearc‐related basin in Central Asian Orogenic Belt: Insights from the petrology and geochemistry of the Shuangjing Schist in Inner Mongolia,China

The Solonker Suture Zone is thought to record the terminal evolution of the Central Asian Orogenic Belt (CAOB) in Inner Mongolia. However, two contrasting interpretations of the timing of suturing of the Solonker Suture Zone exist: (i) Permian to Early Triassic; and (ii) Middle Devonian or Late Devonian to Carboniferous. The Shuangjing Schist is exposed in the Linxi area along the Xar Moron Fault Zone, which marks the southern boundary of the Solonker Suture Zone in the eastern section of the CAOB, and thus provides insight into the timing of suturing of the Solonker Suture Zone. Detailed and systematic analysis of the petrology and geochemistry of the Shuangjing Schist shows that the Shuangjing Schist developed by greenschist facies prograde metamorphism of a volcanisedimentary rock series protolith. The volcanic parts of the Shuangjing Schist are a calc‐alkaline series with large volumes of intermediate members and subordinate acidic members. Volcanism occurred in a magmatic arc on the continental margin and was induced by subduction‐related magmatism resulting from mantle metasomatism. The sedimentary parts of the Shuangjing Schist reflect a transition from continental shelf to abyssal plain sedimentation. The formation of the Shuangjing Schist is suggested to be related to closure of an arc/forearc‐related ocean basin. The timing is constrained by a laser ablation inductively coupled plasma–mass spectrometry (LA‐ICP–MS) U–Pb magmatic zircon age of 298 ± 2 Ma from a carbonaceous biotite–plagioclase schist that was intruded by granite at 272 ± 2 Ma. In the Linxi area, southward subduction of the arc/forearc basin led to uplift, thickening, collapse, and erosion of the overriding continental crust. Collapse induced extension and widespread magmatism along the volcanic arc at the northern margin of the North China Craton. The closure of the arc/forearc‐related oceanic basin led to the formation of Late Permian to Middle Triassic collisional granites and the subsequent end of the collision of the Solonker Suture Zone.     

SHRIMP dating of magmatism in the Hitachi metamorphic terrane,Abukuma Belt,Japan: Evidence for a Cambrian volcanic arc

Ion microprobe dating of zircon from meta‐igneous samples of the Hitachi metamorphic terrane of eastern Japan yields Cambrian magmatic ages. Tuffaceous schist from the Nishidohira Formation contains ca 510 Ma zircon, overlapping in age with hornblende gneiss from the Tamadare Formation (ca 507 Ma), and meta‐andesite (ca 507 Ma) and metaporphyry (ca 505 Ma) from the Akazawa Formation. The latter is unconformably overlain by the Carboniferous Daioin Formation, in which a granite boulder from metaconglomerate yields a magmatic age of ca 500 Ma. This date overlaps a previous estimate for granite that intrudes the Akazawa Formation. Intrusive, volcanic, and volcaniclastic lithologies are products of a Cambrian volcanic arc associated with a continental shelf, as demonstrated by the presence of arkose and conglomerate in the lowermost Nishidohira Formation. Granitic magmatism of Cambrian age is unknown elsewhere in Japan, except for a single locality in far western Japan with a similar geological context. Such magmatism is also unknown on the adjacent Asian continental margin, with the exception of the Khanka block in far northeastern China. A ‘great hiatus’ in the Paleozoic stratigraphy of the Sino–Korean block also exists in the Hitachi terrane between Cambrian volcanic arc rocks and Early Carboniferous conglomerate, and may indicate a common paleogeographic provenance.     

Relationship between the Ordovician and Carboniferous–Permian collisional events in the southeastern Tunka bald mountains, East Sayan (southwestern framing of the Siberian Platform)

Granites from the Tunka pluton of the Sarkhoi complex, located in the eastern Tunka bald mountains (East Sayan), have been dated at the Middle Ordovician (462.6 ± 7.8 Ma) by LA ICP MS. The granites of the Sarkhoi complex within the studied area cut a foldthrust structure consisting of deformed fragments of the Vendian (Ediacaran)–Early Cambrian cover of the Tuva–Mongolian microcontinent (Upper Shumak metaterrigenous formation, Gorlyk carbonate formation). The red-colored conglomerates and sandstones of the Late Devonian–Early Carboniferous(?) Sagan-Sair Formation overlie the eroded surface of the Tunka pluton granites in the eastern Tunka bald mountains. The Sagan-Sair Formation, in turn, is overlain along a low-angle thrust by a group of tectonic sheets, which comprises the volcanic and carbonate sediments of the Tolta Formation, biotitic schists, and plagiogneisses with garnet amphibolite bodies. Two nappe generations have been revealed on the basis of the described geologic relationships, the Middle Ordovician age of the Tunka pluton granites, and numerous Late Paleozoic Ar–Ar dates of syntectonic minerals from the metamorphic rocks in the area. The first thrusting stage was pre-Middle Ordovician, and the second, Late Carboniferous–Permian. The Lower Paleozoic thrust structure resulted from the accretion of the Tuva–Mongolian microcontinent to the Siberian Platform. The Late Paleozoic nappes resulted from intracontinental orogeny and the reactivation of an Early Paleozoic accretionary belt under the effect of the Late Paleozoic collisional events.     

Late Mesozoic magmatism of the Jiurui mineralization district in the Middle–Lower Yangtze River Metallogenic Belt, Eastern China: Precise U–Pb ages and geodynamic implications

The Middle–Lower Yangtze River metallogenic belt (MLYRMB), extending from Daye in Hubei Province in the west to Zhenjiang in Jiangsu Province in the east, hosts a number of large polymetallic (Cu–Au–Mo, Fe, Zn, Pb, and Ag) deposits and constitutes one of the most important metallogenic belts in China. The Cu–Au–Mo deposits in the Jiurui district are an important component of the MLYRMB. In this study we carried out precise and detailed zircon U–Pb dating for all types of magmatic rocks from the Wushan ore deposit in the Jiurui district. Three samples of Cu–Au–Mo-related porphyries from different ore belts at Wushan were analyzed and yielded zircon U–Pb ages of 148.0 ± 1.0 Ma, 145.4 ± 0.9 Ma and 147.3 ± 0.9 Ma, respectively. A series of dykes were emplaced immediately following the Cu–Au–Mo-related porphyries at Wushan. A dark-colored basic dyke which intruded into the granodiorite porphyry at Wujia gold deposit near Wushan was dated at 144.5 ± 1.2 Ma. Two lamprophyre dykes taken from the north ore belt at Wushan underground mining stops were dated at 143.6 ± 0.9 Ma and 144.3 ± 0.9 Ma, respectively. A late-stage dyke which was also taken from the Wushan north ore belt yielded an age of 142.6 ± 1.0 Ma and might represent the end of magmatism in the Wushan ore deposit. These new geochronological data demonstrate that the time range of magmatism in the Wushan ore deposit is approximately between 148 Ma and 143 Ma, showing that the magmatic activity at Wushan was rapid and intensive. The ages of Cu–Au–Mo-related porphyries from other areas in the Jiurui district, such as the Dongleiwan, Yangjishan and Chengmenba ore deposits, were also measured and yielded zircon U–Pb ages of 141.5 ± 1.7 Ma, 143.4 ± 1.4 Ma and 146.6 ± 1.0 Ma, respectively. Combined with those previously reported zircon U–Pb age results from the Jiurui district, the present age data set demonstrates that extensive magmatism in the Jiurui district was coeval and intensive, marked by a magmatic activity in the age range of 148 to 138 Ma and peaked between 148 Ma and 142 Ma. According to the statistics of all those precise zircon U–Pb ages, the Cu–Au–Mo-related porphyries in the Edong and Tongling districts in the MLYRMB show similar ages, and they have a slightly younger peak age and a longer duration than that of the Jiurui district. The geographic shape of the MLYRMB in the Cretaceous shows an arcuate structure, the Jiurui district is located at the transitional point of the arcuate structure and the Edong and Tongling districts are situated on both sides of the arcuate structure. Considering that the Jiurui district has a slightly older peak age and a shorter duration of magmatic activity than that in the Edong and Tongling districts, it seems that the arcuate structure of the MLYRMB played an important role in the formation of these Cu–Au–Mo-related porphyries. Consequently, we suggest that the genesis of the Late Mesozoic magmatic rocks along the MLYRMB may have been due to a tectonic activity developed from southeast to northwest, which probably has a close relationship with the subduction of the paleo-Pacific plate beneath the Eurasian plate in Mesozoic times.     

广西西江经济带产业园区发展水平综合评价

广西西江经济带是未来我国南方地区开发轴带的重要组成部分,沿江地区产业集聚态势明显,承载产业集聚的产业园区迅速发展,但产业园区无序竞争、产业结构雷同、土地产出率低等问题制约沿江产业园区健康有序发展.通过总结沿江产业园区的发展特点,分析影响沿江产业园区发展的因素,认为区域发展基础、园区发展基础、园区发展潜力和园区发展约束条...