从洋壳俯冲到陆壳俯冲和碰撞：来自羌塘中西部地区榴辉岩和蓝片岩地球化学的证据

羌塘中部晚三叠世低温/高压变质带是目前青藏高原内部延伸规模最大的高压变质带,但大量关键高压变质岩石出露地区地球化学资料匮乏,严重制约了对高压变质带原岩建造以及构造演化的全面认识。本文以羌塘中西部地区尚无地球化学资料的果干加年山榴辉岩和红脊山蓝片岩为研究对象,进行了系统的地球化学以及原岩恢复工作。研究表明,果干加年山榴辉岩呈透镜状产于围岩石榴石多硅白云母片岩和少量大理岩中,其原岩为亚碱性玄武岩,具有较低的稀土总量(∑REE=51.19×10-6~59.43×10-6)和轻稀土亏损的特征[(La/Yb)N=0.59~0.70],不具有Nb、Ta、Ti的亏损,与典型的N-MORB特征一致,暗示其原岩可能来源于亏损的地幔源区,形成于洋中脊环境。红脊山地区基性蓝片岩的原岩为碱性玄武岩-亚碱性玄武岩,具有高的TiO2(2.97%~4.14%)和P2O5(0.29%~0.48%)含量,富集轻稀土元素[(La/Yb)N=6.10~11.6]和高场强元素,地球化学特征类似于OIB。但是这些基性蓝片岩与大量的陆源碎屑岩伴生产出,且具有明显的硅铝质上地壳物质混染的特征,与南羌塘地区二叠纪大陆板内基性岩墙的产出特征以及地壳混染特征一致,可能是其俯冲消减的产物。通过本文研究结果并结合区域内已识别出的E-MORB型洋壳和洋岛/海山物质深俯冲的证据,我们认为羌塘中部晚三叠世高压变质带以洋壳物质深俯冲为主,同时亦保留了部分陆壳物质俯冲的证据,暗示大洋向北俯冲消减结束之后,又牵引至少一部分南羌塘北缘陆壳物质经历了随后的俯冲过程。     

Correlation analysis and partial least square modeling to quantify typical minerals with Chang＇E-3 visible and near-infrared imaging spectrometer＇s ground validation data

In 2013, Chang＇E-3 program will develop lunar mineral resources in-situ detection. A Visible and Near-infrared Imaging Spectrometer （VNIS） has been selected as one payload of CE-3 lunar rover to achieve this goal. It is critical and urgent to evaluate VNIS＇ spectrum data quality and validate quantification methods for mineral composition before its launch. Ground validation experiment of VNIS was carried out to complete the two goals, by simulating CE-3 lunar rover＇s detection environment on lunar surface in the laboratory. Based on the hyperspectral reflectance data derived, Correlation Analysis and Partial Least Square （CA-PLS） algorithm is applied to predict abundance of four lunar typical minerals （pyroxene, plagioclase, ilmenite and olivine） in their mixture. We firstly selected a set of VNIS＇ spectral parameters which highly correlated with minerals＇ abundance by correlation analysis （CA）, and then stepwise regression method was used to find out spectral parameters which make the largest contri- butions to the mineral contents. At last, functions were derived to link minerals＇ abundance and spectral parameters by partial least square （PLS） algorithm. Not considering the effect of maturity, agglutinate and Fe~, we found that there are wonderful correlations between these four minerals and VNIS＇ spectral parameters, e.g. the abundance of pyroxene correlates positively with the mixture＇s absorption depth, the value of absorption depth added as the in- creasing of pyroxene＇s abundance. But the abundance of plagioclase correlates negatively with the spectral parame- ters of band ratio, the value of band ratio would decrease when the abundance of plagioclase increased. Similar to plagioclase, the abundance of ilmenite and olivine has a negative correlation with the mixture＇s reflectance data, if the abundance of ilmenite or olivine increase, the reflectance values of the mixture will decrease. Through model validation, better estimates of pyroxene, plagioclase and ilmenite＇s abundances are given. It is concluded that VNIS has the capability to be applied on lunar minerals＇ identification, and CA-PLS algorithm has the potential to be used on lunar surface＇s in-situ detection for minerals＇ abundance prediction.     

Studies on the Coral Reefs of the South China Sea: From Global Change to Oil-Gas Exploration

Studies on the coral reefs of the South China Sea (SCS) was the theme of the 6th Session of the 3rd Conference on Earth System Science (CESS) in Shanghai, 2014. This session discussed the most recent study developments on the SCS coral reefs, including coral reefs’ responses to global changes, coral reefs’ records on past climatic variations, and the activities about constructions and oil gas explorations in the coral reefs areas of the SCS. Disturbed by intensive anthropogenic activities and global climate warming, coral reefs in the SCS have declined dramatically, reflecting the up to 80% decrease of living coral cover and many areas having less than 20% of living coral cover. Geochemical data of SCS coral skeletons clearly show that since the Industry Revolution, the pollution situation of the SCS have dramatically increased and the seawater pH values have been continuously lowering, i.e. oceanic acidification. All these environmental phenomenon are further stressing the healthy development of the coral reef ecosystem in the SCS. Meanwhile, the poor coral reef ecosystems in the SCS are facing more anthropogenic disturbances such as coastal developments and engineering constructions. Obviously, the SCS coral reefs will be faced with more environmental challenges in the coming future. We therefore suggest that the policy makers should realize the extreme importance and the fragile of the coral reef ecosystems, and scientifically and with great cautions design construction project when in coral reef areas. We initiated the concept of “green engineering” for future developments in coral reef areas. Coral reefs are widely spreading in the whole SCS, and most of them developed since Miocene. Variations in coral reef structures provide good future oil-gas exploration. Because the SCS coral reefs have a long-developing history and a wide spatial distribution, they provide great potential in recording past environmental changes.     

大兴安岭地区古生代构造格架重建:来自俯冲增生杂岩研究进展

大兴安岭地区古生代处于古亚洲洋闭合阶段,其间发育众多的弧盆系和蛇绿岩带,笔者等在大兴安岭地区1: 1 000 000地质编图和野外地质调研基础上,应用“洋板块地质”学术思想在大兴安岭地区元古宙、古生代地质体中划分出一系列“俯冲增生杂岩”、地块基底残块、岛弧、弧前盆地、弧后盆地等构造单元,结合陆(地)块和岩浆弧、弧前盆地、弧后盆地和“俯冲增生杂岩”的时空展布,划分出9条俯冲增生杂岩带,其中新识别出3条俯冲增生杂岩带。俯冲增生杂岩带主要分布于兴蒙造山带内部各地块之间和地块与大型岛弧带之间,相当于地块间及地块与岛弧带间的缝合带。依据俯冲增生杂岩带两侧对应的陆(地)块、岛弧带等构造级别,归并出5条结合带。俯冲增生杂岩带的展布方向以北东向为主,时代自北向南依次变新,从早奥陶世演化到中—晚二叠世,暗示古亚洲洋洋盆向大兴安岭地区陆(地)块俯冲作用最早发生在北部额尔古纳一带,逐渐向南后撤,不断形成新的洋壳和产生俯冲增生作用,相应的活动陆缘从北部额尔古纳地块向南逐渐增生,配套弧盆系时代也逐渐向南变新。早—中三叠世至西拉木伦一带发生陆-陆拼贴,完成华北板块与西伯利亚板块的对接。通过对大兴安岭地区古生代“俯冲增生杂岩”的研究,重建了大兴安岭地区古生代构造格架,提高了古亚洲洋东段洋-陆转换的研究程度。     

早古生代古亚洲洋俯冲作用:来自新疆哈尔里克侵入岩的锆石U-Pb年代学、岩石地球化学和Sr-Nd同位素证据

新疆哈尔里克造山带的形成时间(早古生代/晚古生代)及其构造属性(岛弧/弧后盆地)一直是有争议的问题。本文选择位于哈尔里克带内的奥尔达乌台克侵入体,对其成因及所揭示的地质意义进行了探讨。奥尔达乌台克岩体由一套成份连续的岩石组合构成,包括辉长岩、辉长闪长岩、闪长岩和花岗闪长岩。对闪长岩及其内部暗色包体进行的LA-ICP-MS锆石U-Pb定年结果显示两者同时形成于~450Ma,为晚奥陶世岩浆活动的产物。岩石学和地球化学证据反映奥尔达乌台克岩体普遍具有富H2O、高fO2的湿岩浆性质,富集LREE、Sr、Ba等大离子亲石元素(LILE)而亏损Nb、Ta、Ti等高场强元素(HFSE),与典型的岛弧岩浆岩类似。高放射成因Nd(εNd(t)=+4.4~+5.9)和低初始Sr(0.7032~0.7044)同位素组成表明偏基性的岩浆很可能起源于年轻的俯冲带岩石圈地幔,生成的镁铁质岩浆一部分与壳源长英质熔体发生混合形成各类岩浆,另一部分则是经历演化后(分离结晶)直接添加到地壳中。因此,壳幔岩浆混合作用和幔源物质的直接加入是古亚洲洋俯冲阶段陆壳增生的两种主要方式。Sr-Nd同位素模拟排除了区内存在古老前寒武纪陆壳的可能,陆壳主体应该是年轻的古生代大洋岛弧和洋壳。哈尔里克早古生代岛弧的确立改变了该带是泥盆纪岛弧或弧后盆地的原有认识,将古亚洲洋俯冲作用的时间追溯至奥陶纪。     

《甘肃政务专用图集》的设计与编制

《甘肃政务专用图集》是一本为政务应用提供地图保障服务的综合性地图集。本文主要介绍了该图集的设计思路、规格、编制内容、编制的技术流程以及编绘方法等,并总结了图集编制的特点和意义。     

政府规划约束下的城市空间增长多智能体模拟模型

构建政府规划约束下的包含多种类型智能体和环境因素的城市空间增长多智能体模拟模型,通过居民、开发商和政府三类智能体之间以及智能体与环境之间的相互作用模拟了城市空间增长情况。模型将城市建设用地规划区纳入政府的土地利用政策,探讨了政府规划因素对城市建设用地增长的影响,并根据土地集约利用的原则对模拟结果进行了优化。在Repast和ArcGIS的实验环境下,以南京市中心城区(长江以南)为研究区设置了四组土地利用情景,模拟了2001-2007年研究区的城市建设用地增长情况,对比不同情景下模型的模拟精度,说明正确合理的政府规划引导对城市空间增长的重要作用以及对模拟结果进行优化的必要性。该模型有助于揭示城市空间增长机制,为政府宏观调控政策和规划制定提供参考。     

Response and recovery of the Comanche carbonate platform surrounding multiple Cretaceous oceanic anoxic events,northern Gulf of Mexico

The ubiquity of carbonate platforms throughout the Cretaceous Period is recognized as a product of high eustatic sea-level and a distinct climatic optimum induced by rapid sea-floor spreading and elevated levels of atmospheric carbon-dioxide. Notably, a series of global oceanic anoxic events (OAEs) punctuate this time-interval and mark periods of significantly reduced free oxygen in the world's oceans. The best records of these events are often from one-dimensional shelf or basin sections where only abrupt shifts between oxygenated carbonates and anoxic shales are recorded. The Comanche Platform of central Texas provides a unique opportunity to study these events within a well-constrained stratigraphic framework in which their up-dip and down-dip sedimentologic effects can be observed and the recovery of the platform to equilibrium states can be timed and understood. Stable isotope data from whole cores in middle Hauterivian through lower Campanian mixed carbonate-siliciclastic strata are used to construct a 52-myr carbon isotope reference profile for the northern Gulf of Mexico. Correlation of this composite curve to numerous global reference profiles permits identification of several anoxic events and allows their impact on platform architecture and facies distribution to be documented. Oceanic anoxic events 1a, 1b, 1d, and 2 occurred immediately before, after, or during shale deposition in the Pine Island Member, Bexar Member, Del Rio Formation, and Eagle Ford Group, respectively. Oceanic anoxic event 3 corresponds to deposition of the Austin Chalk Group. Platform drowning on three occasions more closely coincided with globally recognized anoxic sub-events such as the Fallot, Albian-Cenomanian, and Mid-Cenomanian events. This illustrates that the specific anoxic event most affecting a given carbonate platform varied globally as a function of regional oceanographic circumstances.Using chemo- and sequence-stratigraphic observations, a four-stage model is proposed to describe the changing facies patterns, fauna, sedimentation accumulation rates, platform architectures, and relative sea-level trends of transgressive-regressive composite sequences that developed in response to global carbon-cycle perturbations. The four phases of platform evolution include the equilibrium, crisis, anoxic, and recovery stages. The equilibrium stage is characterized by progradational shelf geometries and coral-rudist phototrophic faunal assemblages. Similar phototrophic fauna typify the crisis stage; however, incipient biocalcification crises of this phase led to retrogradational shelf morphologies, transgressive facies patterns, and increased clay mineral proportions. Anoxic stages of the Comanche Platform were coincident with back-ground deposition of organic-rich shale on drowned shelves and heterotrophic fauna dominated by oysters or coccolithophorids. Eustatic peaks of this stage were of moderate amplitude (∼30 m), yet relative sea-level rises were greatly enhanced by reduced sedimentation rates. In the recovery stage, heterotrophic carbonate factories re-established at the shoreline as progradational ramp systems and sediment accumulation rates slowly increased as dysoxia diminished. Full recovery to equilibrium conditions may or may not have followed. Geochemical and stratigraphic trends present in the four stages are consistent with increased volcanism along mid-ocean ridges and in large-igneous provinces as primary drivers of Cretaceous OAEs and the resulting transgressive-regressive composite sequences.     

浙江中部芙蓉山花岗斑岩及包体岩石地球化学研究

花岗岩的源区、温压条件及与其他岩石的共生组合的研究可以限定其形成构造背景,了解其形成的深部动力学过程.本文对浙江中部中生代芙蓉山花岗斑岩及其暗色包体开展了全岩主微量元素、锆石U-Pb年代学和Hf同位素、Ti温度计和全岩Sr—Nd同位素研究,探讨芙蓉山花岗斑岩的成因类型、源区特征及其与镁铁质包体之间的关系,并进一步限定其...     

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