新疆东天山十里坡自然铜矿化区马头滩组玄武岩锆石LA-ICPMS U-Pb年龄及其意义

新疆北部东天山十里坡地区近年来新发现了与玄武岩有关的自然铜矿化这一新类型。自然铜的赋矿地层-马头滩组中的赋矿玄武岩锆石 LA-ICPMS 年龄为307±4Ma,对应于晚石炭世,显示该套赋矿地层属于上石炭统。从该区自然铜赋矿火山岩所限定的时间看,成矿背景应属于后碰撞环境。东天山十里坡地区自然铜矿化的构造背景、成矿系统和矿化类型与峨眉山玄武岩自然铜矿化和美国基威诺铜矿床均存在差异,自然铜矿化的成因可能也存在差异。     

三峡引水工程秦巴段输水隧洞稳定性分析

三峡引水工程秦巴段隧洞总长占线路总长的80%。为了分析隧洞施工及运营中可能发生的工程地质问题,在地质调查、地应力测量和岩石力学参数测试的基础上,利用Ansys有限元软件对引水工程北部不同深度、不同截面形态的隧洞围岩的应力重分布情况进行了模拟计算,得到了圆形隧洞、城门形隧洞和马蹄形隧洞围岩的应力分布结果。利用Hoek-Brown强度准则,得到了隧洞围岩的强度/应力比值,进而对不同深度、不同截面形态的隧洞围岩的稳定性进行了分析。初步认为:隧洞埋深小于1000m时,应优先考虑圆形隧洞和马蹄形隧洞;埋深大于1000m时,应优先考虑城门形隧洞。这项研究成果为引水工程深埋隧洞的设计提供了参考依据。     

青海南部杂多地区超镁铁质-镁铁质岩石的特征及Ar—Ar定年

通过野外地质研究和室内岩相学、岩石地球化学研究,在位于青藏高原中部的青海杂多地区的双湖-澜沧江结合带中发现了一套超镁铁质岩、镁铁质岩。该超镁铁质岩、镁铁质岩沿北西—南东向区域构造线多呈岩脉状侵入在早石炭世杂多群中,局部呈构造透镜体分布在断裂带中或呈包体分布在白垩纪花岗岩中,出露规模不大,局部侵入体具有层状侵入杂岩体的特征。主要岩石类型为辉石橄榄岩、辉长岩、辉长辉绿岩,岩石地球化学具高Ti、Fe、Al、Ga和LREE中等富集的特征。橄榄岩中角闪石的~(40)Ar/~(39)Ar同位素测年得到275.3Ma±1.9Ma的坪年龄,表明这套超镁铁—镁铁质岩石可能为早、中二叠世弧后盆地拉张的产物。     

成都经济区农业生态系统土壤镉通量研究

以四川成都经济区农业生态系统中的重金属Cd为对象,对其在土壤中的输入输出通量进行初步探索。综合各方面的因素,确定以大气干湿沉降、灌溉水、化肥为输入途径和农作物为输出途径进行研究。经过计算,经济区大气干湿沉降通量平均值为17.76g/hm2·a,灌溉水和化肥通量明显较低,三者对土壤Cd污染的贡献率分别为86%、10%和4%。对于6个不同的地区,三者比例略有差别,大气干湿沉降所占比例最高达94%,最低也达到了77%。Cd通过农作物收割输出的量相对较小。土壤Cd年净增量主要受大气干湿沉降的制约,因此大气环境质量应是重点监控的对象。以耕作土体为研究介质,经估算,当前的Cd年平均通量可引起土壤Cd的质量分数升高0.006mg/kg。     

Evolution of the Mesozoic Granites in the Xiong''ershan-Waifangshan Region,Western Henan Province,China,and Its Tectonic Implications

Based on the new data of isotopic ages and geochemical analyses, three types of Mesozoic granites have been identified for the Xiong'ershan-Waifangshan region in western Henan Province: high-Ba-SrⅠ-type granite emplaced in the early stage (～160 Ma),Ⅰ-type granite in the middle stage (～130 Ma) and anorogenic A-type granite in the late stage (～115 Ma). Geochemical characteristics of the high-Ba-SrⅠ-type granite suggest that it may have been generated from the thickened lower crust by partial melting with primary residues of amphibole and garnet. Gradual increase of negative Eu anomaly and Sr content variations reflect progressive shallowing of the source regions of these granites from the early to late stage. New 40Ar/39Ar plateau ages of the early-stage Wuzhangshan granite (156.0±1.1 Ma, amphibole) and middle-stage Heyu granite (131.8±0.7 Ma, biotite) are indistinguishable from their SHRIMP U-Pb ages previous published, indicating a rapid uplift and erosion in this region. The representative anorogenic A-type granite, Taishanmiao pluton, was emplaced at～115 Ma. The evolution of the granites in this region reveals a tectonic regime change from post-collisional to anorogenic between～160 Ma and～115 Ma. The genesis of the early- and middle-stageⅠ-type granites could be linked to delamination of subducted lithosphere of the Qiniing orogenic belt, while the late-stage A-type granites represent the onset of extension and the end of orogenic process. In fact, along the Qiniing -Dabie-Sulu belt, the Mesozoic granitoids in western Henan, Dabieshan and Jiaodong regions are comparable on the basis of these temporal evolutionary stages and their initial 87Sr/86Sr ratios, which may suggest a similar geodynamic process related to the collision between the North China and Yangtze cratons.     

陆相沉积的天文地层研究方法简介——以井下地层为例

通过对我国大陆三十余口井的测井资料研究成果,归纳出对陆相地层进行天文地层研究的方法。介绍了所用的新的天文周期理论值、测井资料的选取及预处理方法,重点说明谱分析的数据点数的选定、不同参数(自然伽玛、自然电位和岩屑)的测井资料谱分析结果的对比,以实例说明如何选定主要优势旋回和AR值,以及FIR数字滤波器的基本性质和数字滤波结果,小波分析的特点和通过小波图进行调频的方法,并介绍了地层单位的延续时间计算和年龄确定方法。     

东营凹陷牛庄地区沙三段层序地层分析

山东济阳坳陷东营凹陷牛庄地区沙三段层序地层分析是在三级层序划分的基础上,通过对沉积体系发育特征和气候旋回单元的识别和解剖,建立了高精度层序地层单元的基本构型。气候旋回包含了从干旱枯水期到潮湿湖泛期的完整过程,沉积响应为受湖平面变化、沉积物供给等因素控制的多种方式叠置的湖底扇和前积体等,多期气候旋回叠合构成了湖泊层序的基本面貌。通过气候旋回的识别,可以对不同级别层序间的包含关系,以及高精度层序的内部构成进行分析和讨论。     

五大连池近代火山老黑山火烧山火山喷发过程的考察研究

作者在已有工作的基础上,以当代火山学的研究思路和观点,为恢复五大连池两个近代火山,老黑山火烧山的喷发历史过程进行了野外考察研究工作。老黑山火山锥是由三套不同的碎屑堆积物组成。在锥体的南侧、东侧和西侧以及北测和北西侧有５个熔岩溢出口,按它们形成先后关系,认为有早、中、晚三期熔岩流。本文还对老黑山火山锥上的寄生火山、结壳熔岩与渣状熔岩的分布、流动特点及形成的控制因素进行了分析讨论。最后得出结论：老黑山火山是经多期次喷发活动形成的。火烧山火山锥是一碎屑化泡沫化程度很低的浮岩块和熔岩碎块组成,同老黑山有明显区别。     

The Characteristics of Spinels in Mantle-derivedXenoliths in Cenozoic Basalts from Eastern Chinaand Their Thermal States

The colours and chemical composition variations of 160 spinels in peridotite and pyroxenite xenoliths from Cenozoic basalts in eastern China and their petrogeneses have been studied in detail. The relationships between major elements of spinels are discussed. The equilibrium temperatures, pressures and oxygen fugacities of spinels and their coexisting olivines, orthopyroxenes and clinopyroxenes have been determined using the Brey-kohler' s T-P calculation methods (1990) and Ballhaus' fo2 calculation method (1991). The relationships betweenthe composition and the equilibrium temperatures, pressures or oxygen fugacities of spinels in peridotite xenoliths from the basalts and the stable field of the spinels in the upper mantle have been shown.     

Distribution Patterns of Pentacyclic TriterpenoidHydrocarbons in Low-Mature Source Rocksfrom Eastern China

Four typical distribution patterns of pentacyclic triterpenoid hydrocarbons (types A-D) are distinguished in the low-mature source rocks from eastern China. Type A has a relatively high content of pentacyclic triterpenes. It exists in immature sediments and the distribution and abundance of triterpenes vary with the maturity of the sediments. An unknown C30 triterpene (UCT2) has also been detected in very shallow sediments. This compound is very unstable and disappears rapidly with the increase of depth. Type B is characterized by a relatively high amount of 17α(H), 21β(H)-30-homohopane. This kind of distribution pattern is common in coals and terrestrial sediments of low maturity. Type C has a relatively high content of diahopane and neohopane series. The analysis shows that this distribution pattern may have an indirect relationship with the input of higher plants despite its microbial source. There are C30-unconfirmed triterpane (UCT2) and a relatively high content of C35 hopane in type D. The dist