莺歌海盆地DF1-1-11井有孔虫生物地层与沉积环境研究

结合ODP184航次及2008年国际地层表等研究成果,对莺歌海盆地基准井DF1-1-11井岩屑地层(630～3508 m)的有孔虫定量分析资料进行研究,建立可靠的生物地层及年代地层格架,并通过对钻井中有孔虫丰度、分异度、浮游比例、组合特征及古水深估算分析,讨论了DF1-1一11井中中新世以来的沉积环境演化.研究结果...     

Cenozoic volcanic rocks in the Belog Co area, Qiangtang, northern Tibet, China： Petrochemical evidence for partial melting of the mantle-crust transition zone

Neogene volcanic rocks in the Belog Co area, Qiangtang, northern Tibet, are represented by a typical intermediate-basic and intermediate alkaline rock association, with latite-trachyte as the main rock type. The results of chemical analysis are: SiO2=52%–62%, Al2O3>15%, Na2O/K2O>1 and MgO<3.30%. In addition, the volcanic rocks are LREE-enriched with LREE/HREE=10–13, (La/Yb)N=15–19, and show a weak negative Eu anomaly with δEu=0.71–0.89. The close relationship between Mg# and SiO2 and the co-variation of the magmatophile elements and ultra-magmatophile elements such as La/Sm-La and Cr-Tb indicate that this association of volcanic rocks is the product of comagmatic fractional crystallization. The rock association type and lower Sm/Yb values (Sm/Yb=3.23–3.97) imply that this association of volcanic rocks should have originated from partial melting of spinel lherzolite in the lithospheric mantle. On the other hand, the weak negative Eu anomaly and relative depletion in Nb, Ta and Ti reflect the features of terrigenous magma. So the Neogene Belog Co alkaline volcanic rocks should be the result of partial melting of the special crust-mantle transition zone on the Qinghai-Tibet Plateau.     

<Superscript>40</Superscript>Ar/<Superscript>39</Superscript>Ar chronology and geochemistry of high-K volcanic rocks in the Mangkang basin,Tibet

Our two newly obtained high-quality ⁴⁰Ar/³⁹Ar ages suggest that the high-K volcanic rocks of the Lawuxiang Formation in the Mangkang basin, Tibet were formed at 33.5 ± 0.2 Ma. The tracing of elemental and Pb-Sr-Nd isotopic geochemistry indicates that they were derived from an EM2 enriched mantle in continental subduction caused by transpression. Their evidently negative anomalies in HFSEs such as Nb and Ta make clear that there is an input of continental material into the mantle source. The high-K rocks at 33.5 ± 0.2 Ma in the Mangkang basin may temporally, spatially and compositionally compare with the early one of two-pulse high-K rocks in eastern Tibet distinguished by Wang J. H. et al., implying that they were formed in the same tectonic setting.     

Palynostratigraphy of the Erkovtsy field of brown coal (the Zeya-Bureya sedimentary basin)

The Erkovtsy brown coal field in the northwestern Zeya-Bureya sedimentary basin (129°–130° E, 46°–47° N) is structurally confined to southern flank of the Mesozoic-Cenozoic Belogor’e depression. The verified stratigraphic scheme of the coalfield sedimentary sequence is substantiated by palynological data on core samples from 18 boreholes sampled in the course of detailed prospecting and by paleobotanical analysis of sections in the Yuzhnyi sector of the coalfield (data of 1998 by M.A. Akhmetiev and S.P. Manchester). Sections of the Erkovtsy, Arkhara-Boguchan, and Raichikha brown-coal mines are correlated. Stratigraphic subdivisions distinguished in the studied sedimentary succession are the middle and upper Tsagayan subformations (the latter incorporating the Kivda Beds), Raichikha, Mukhino, Buzuli, and Sazanka formations.     

柴达木盆地东部新生代盆地结构与演化

本文对柴达木盆地东部新生代盆地结构和构造演化进行了研究.地震剖面揭示柴达木盆地东部新生界分别向南、北盆地边缘变薄和尖灭,盆地北部被欧龙布鲁克山和埃姆尼克山隆起强烈改造.通过对新生代地层厚度横向变化以及地层剖面分析,确定欧北断裂自中新世晚期开始向北逆冲,导致欧龙布鲁克山发生隆升和德令哈凹陷的形成.埃北断裂从上新世开始活动,与欧北断裂同时向北逆冲,导致德令哈凹陷进一步沉降,形成厚度达2600 m的狮子沟组.埃南断裂在第四纪开始大规模向南逆冲,不仅造成其北侧的欧龙布鲁克山和埃姆尼克山隆起强烈抬升和向南推覆,而且导致南侧霍布逊凹陷的形成,成为柴达木盆地第四纪沉积中心.早期提出的前陆盆地和背驮式盆地模型显然不能解释柴达木盆地东部新生代构造格架和演化历史.本次研究认为柴达木盆地东部的形成是强烈的水平挤压作用导致地壳发生大规模褶皱的结果,即柴达木盆地东部新生代是一个大规模向斜.该向斜盆地模型很好地解释了新生代地层向盆地边缘减薄以及沉积中心主要位于盆地中部等现象.了解柴达木盆地东部构造发展对了解青藏高原侧向扩展具有重要意义.     

塔里木盆地中新生代海侵和海相地层研究的新进展

中新生代海侵是塔里木盆地地质发展史上的重要事件之一。通过对新近发现的古生物化石和海相地层资料研究，本文提出了早白垩世、晚白垩世、古近纪的海侵范围的新认识。同时，依据露头和钻井资料提出了中新世海水分布的新范围。这些新成果对厘定塔里木盆地中新生代地层时代，建立整个盆地中新生代地层格架和油气远景分析具有重要意义。     

Early Cretaceous volcanic rocks and Early Cenozoic extrusions of Cape Mary, Schmidt Peninsula, north Sakhalin: Geochemical study

The Early Cretaceous volcanic rocks of the Mariisky sequence and Early Cenozoic extrusive-vent rocks of Cape Mary are exposed at the northwestern extremity of Schmidt Peninsula, north Sakhalin. In chemical composition, all the rocks are subdivided into four groups. Three groups include the volcanic rocks of the Mariisky sequence, which consists, from bottom to top, of calc-alkaline rocks, transitional calc-alkaline-tholeiite rocks, and incompatible element-depleted tholeiites. These rocks show subduction geochemical signatures and are considered as a fragment of the Moneron-Samarga island arc system. Trace-element modeling indicates their derivation through successive melting of garnet-bearing mantle and garnet-free shallower mantle sources containing amphibole; pyroxene; and, possibly, spinel. The mixed subduction and within-plate characteristics of the extrusive vent rocks of Cape Mary attest to their formation in a transform continental margin setting.     

Late Cenozoic Stratigraphy and Paleomagnetic Chronology of the Zanda Basin, Tibet, and Records of the Uplift of the Qinghai-Tibet Plateau

The characteristics of Late Cenozoic tectonic uplift of the southern margin of the Qinghai- Tibet Plateau may be inferred from fluvio-lacustrine strata in the Zanda basin, Ngari, Tibet. Magnetostratigraphic study shows that the very thick fluvio-lacustrine strata in the basin are 5.89- 0.78 Ma old and that their deposition persisted for 5.11 Ma, i.e. starting at the end of the Miocene and ending at the end of the early Pleistocene, with the Quaternary glacial stage starting in the area no later than 1.58 Ma. Analysis of the sedimentary environment indicates that the Zanda basin on the southern Qinghai-Tibet Plateau began uplift at -5.89 Ma, later than the northern Qinghai-Tibet Plateau. Presence of gravel beds in the Guge and Qangze Formations reflects that strong uplift took place at -5.15 and -2.71 Ma, with the uplift peaking at -2.71 Ma.     

阿尔金断裂新生代活动方式及其与柴达木盆地的耦合分析

位于青藏高原北缘的阿尔金左旋走滑断裂是世界上规模最大也是最重要的线性构造之一,其新生代以来的活动方式是限定高原生长机制的重要边界条件.本文在对阿尔金山中不同方向隆起构造进行分析的基础上,综合前人资料论证了阿尔金断裂在晚始新世-中中新世时以基底剪切为主,大规模地表走滑则发生在中中新世以后.对柴达木盆地内近东西向和北西向断裂系统的分布、形态、活动时间进行了详细的分析,发现它们是在不同时间、不同区域、不同控制条件下形成的两套断裂系统,与阿尔金断裂的两阶段活动方式存在很好的耦合关系.柴达木盆地西北侧的沉积和构造特征表明阿尔金山的隆升幅度和范围在中中新世达到最大,随后则逐渐减小,这种变化也与阿尔金断裂从基底剪切到地表走滑的转换非常吻合.     

新生代增温情景下自然火历史的研究

自然火是地球系统的重要组成部分,与气候、植被关系紧密。全球增温情景下,自然火的演化规律和控制因素已经成为学术界的研究热点,通过整理分析自然火实际监测记录、模型模拟结果以及古记录反映的自然火历史,发现还存在一些亟待解决的问题：全球不同增温情景下自然火增多还是减少?其控制因素如何改变?本文选取距今最近的地质历史时期新生代中的典型增温期"中中新世气候适宜期"和"全新世大暖期",对其自然火研究进行分析总结,归纳得出温度是增温情景下自然火的重要控制因素,但是不同地区自然火控制因素有所不同,雨热条件的季节分配、植被类型的演替、雷电和火山活动等因素也对自然火有重要影响。季风区气候变幅大、植被类型丰富,其自然火演化及控制因素具有复杂性,是自然火研究的重要区域,建议在今后研究中,在东亚季风区选择涵盖未来百年可能增温幅度的理想沉积记录,对其记录的自然火历史、增温幅度、植被演替进行系统研究,进而探讨未来增温情景下自然火的演化规律和控制因素。