大别山黄土岭麻粒岩锆石和共生矿物的微量元素分析及其地质意义

对大别山黄土岭麻粒岩中的锆石进行了LA-ICPMS微区微量元素分析.结果表明,黄土岭麻粒岩中锆石的不同区域有不同的微量元素组成,麻粒岩相变质锆石的大多数微量元素含量明显低于岩浆锆石,表明麻粒岩相变质条件下形成的锆石具有较低的微量元素组成.锆石及其共生矿物的微量元素分析结果表明,该麻粒岩中变质锆石Eu负异常是变质锆石形成时长石稳定存在的结果.锆石与石榴子石之间微量元素分配特点表明,变质锆石与石榴子石之间到达了平衡.这些结果表明,该样品的变质锆石形成于麻粒岩相峰期变质阶段,这些变质锆石区域测定的年龄结果对应于麻粒岩相峰期变质作用时间.锆石和共生矿物的微量元素分析对锆石的成因及得到的年龄的解释具有重要的指示意义.锆石与石榴子石之间微量元素的分配特征,不但可以指示锆石与石榴子石之间是否达到平衡,而且可以通过石榴子石这一"桥梁",为锆石的U-Pb年龄提供合理的p-T条件限定.     

最近13万年以来洛川黄土剖面中固定铵态氮的古气候意义

对13万年以来洛川黄土-古土壤序列中固定铵态氮进行了分析.末次间冰期S1古土壤中固定铵态氮含量最高,其次为冰后期S0古土壤,末次冰期形成的马兰黄土最低;而且,固定铵态氮的分布在马兰黄土中也能体现出三次小的低-高值的波动特征.洛川黄土13万年以来固定铵态氮的分布与磁化率和<2μm组分的分布相似.在此基础上,利用马兰黄土中粒度与固定铵态氮的相关关系,计算了S1古土壤中固定铵的分布,并与实测结果进行了对比,推测S1古土壤中固定铵态氮有轻微的损失,尽管如此,S1古土壤中固定铵态氮含量仍然高于黄土.鉴于黄土-古土壤序列中固定铵态氮的分布与粉尘粒度有密切的关系,能与气候变化较好地对应,它可视为反映黄土高原区东亚冬季风强-弱周期性变化较好的替代性指标.     

三沙市南海诸岛底栖海藻区系调查及其与其它相关区系的比较分析

我国海岸线绵长,所属岛屿众多,除了台湾岛和海南岛两个大岛外,还有数以千计的中小沿海岛屿及众多的珊瑚岛,如我国三沙市的南海诸岛—西沙群岛、南沙群岛、东沙群岛和中沙群岛等。根据多年来我国科研人员在该海区的调查研究,对我国三沙市南海诸岛海区的海藻区系进行初步的植物地理学研究,以探讨我国该海域海藻区系的温度性质,以及与邻近海区海藻区系的关系。研究结果表明,我国三沙市南海诸岛底栖海藻区系与北太平洋西部海藻相同种数最多的是区系性质为热带性的南海南区,因此海藻区系的温度性质具有很明显的热带性。另外,三沙市南海诸岛海藻区系与印度洋海藻区系有很多共同成分,两地共有种数高达184种,为南海诸岛海藻总数的63%,进一步证明我国三沙市南海诸岛区系属于暖水性印度—西太平洋区,印—马亚区。     

基于SPOT遥感影像的九段沙潮沟信息提取及分维研究

以长江口九段沙为研究区, 应用灰度形态学提取了九段沙湿地的潮沟信息, 并对提取出的潮沟信息分区域采用网格法进行了分维研究, 得出了九段沙不同区域潮沟的分维值, 并对分维值进行了比较与分析。比较发现, 九段沙不同区域的分维值, 上沙最大, 下沙次之, 中沙最小。而在不同区域的不同岸段中, 处于上沙北部沿岸的潮沟分维值大于上沙其它地区; 处于中沙、下沙西北-东南沿岸的潮沟分维值分别大于中沙、下沙的其它地区。这主要与它们所处地理位置水动力条件不同有关。另外也计算了九段沙南岸与北岸的分维值, 发现南岸的分维值要大于北岸, 这与其发育时间、水动力条件和长江口深水航道工程等有一定联系。     

Geophysical investigations of crust-scale structural model of the Qiongdongnan Basin, Northern South China Sea

Rifting of the Qiongdongnan Basin was initiated in the Cenozoic above a pre-Cenozoic basement, which was overprinted by extensional tectonics and soon after the basin became part of the rifted passive continental margin of the South China Sea. We have integrated available grids of sedimentary horizons, wells, seismic reflection data, and the observed gravity field into the first crust-scale structural model of the Qiongdongnan Basin. Many characteristics of this model reflect the tectonostratigraphic history of the basin. The structure and isopach maps of the basin allow us to reconstruct the history of the basin comprising: (a) The sediments of central depression are about 10 km thicker than on the northern and southern sides; (b) The sediments in the western part of the basin are about 6 km thicker than that in the eastern part; (c) a dominant structural trend of gradually shifting depocentres from the Paleogene sequence (45–23.3 Ma) to the Neogene to Quaternary sequence (23.3 Ma–present) towards the west or southwest. The present-day configuration of the basin reveals that the Cenozoic sediments are thinner towards the east. By integrating several reflection seismic profiles, interval velocity and performing gravity modeling, we model the sub-sedimentary basement of the Qiongdongnan Basin. There are about 2–4 km thick high-velocity bodies horizontal extended for a about 40–70 km in the lower crust (v > 7.0 km/s) and most probably these are underplated to the lower stretched continental crust during the final rifting and early spreading phase. The crystalline continental crust spans from the weakly stretched domains (about 25 km thick) near the continental shelf to the extremely thinned domains (<2.8 km) in the central depression, representing the continental margin rifting process in the Qiongdongnan Basin. Our crust-scale structural model shows that the thinnest crystalline crust (<3 km) is found in the Changchang Sag located in the east of the basin, and the relatively thinner crystalline crust (<3.5 km) is in the Ledong Lingshui Sag in the west of the basin. The distribution of crustal extension factor β show that β in central depression is higher (>7.0), while that on northern and southern sides is lower (<3.0). This model can illuminate future numerical simulations, including the reconstruction of the evolutionary processes from the rifted basin to the passive margin and the evolution of the thermal field of the basin.     

Structural differences between the western and eastern Qiongdongnan Basin: evidence of Indochina block extrusion and South China Sea seafloor spreading

Located at the intersection between a NW-trending slip system and NE-trending rift system in the northern South China Sea, the Qiongdongnan Basin provides key clues for us to understand the proposed extrusion of the Indochina Block along with Red River Fault Zone and extensional margins. In this paper we for the first time systematically reveal the striking structural differences between the western and eastern sector of the Qiongdongnan Basin. Influenced by the NW-trending slip faults, the western Qiongdongnan Basin developed E–W-trending faults, and was subsequently inverted at 30–21 Ma. The eastern sector was dominated by faults with NE orientation before 30 Ma, and thereafter with various orientations from NE, to EW and NW during the period 30–21 Ma; rifting display composite symmetric graben instead of the composite half graben or asymmetric graben in the west. The deep and thermal structures in turn are invoked to account for such deformation differences. The lithosphere of the eastern Qiongdongnan Basin is very hot and thinned because of mantle upwelling and heating, composite symmetric grabens formed and the faults varied with the basal plate boundary. However, the Southern and Northern Uplift area and middle of the central depression is located on normal lithosphere and formed half grabens or simple grabens. The lithosphere in the western sector is transitional from very hot to normal. Eventually, the Paleogene tectonic development of the Qiongdongnan Basin may be summarized into three stages with dominating influences, the retreat of the West Pacific subduction zone (44–36 Ma), slow Indochina block extrusion together with slab-pull of the Proto-South China Sea (36–30 Ma), rapid Indochina block extrusion together with the South China Sea seafloor spreading (30–21 Ma).     

烟台港倾倒区表层沉积物重金属的富集特征及风险评价

分析了2001~2011年烟台港倾倒区表层沉积物中6种重金属的含量及时空分布特征,采用地累积指数(Igeo)和潜在生态风险指数(ERI)对重金属富集现状及潜在生态风险进行评价。结果显示：历次调查重金属含量均较低且空间分布差异小,与黄海背景值相比, Cd和Cu出现一定程度的富集。ERI评价表明2011年倾倒区潜在生态风险性较低,年际变化顺序为：2008年＞2006年＞2009年＞2011年＞2001年, Cd和Hg是近年来的主要风险因子。     

婆罗洲地质构造特征及其对南海南部盆地的影响

南海南部曾母、文莱—沙巴盆地油气资源丰富,已发现一大批油气田及含油气构造。曾母盆地南部与文莱—沙巴盆地油气的生成、运移和聚集与婆罗洲地块息息相关。婆罗洲地块地质特征复杂,自古新世开始,古南海逐渐消失,与婆罗洲地块发生碰撞,中新世开始隆升造山。在这种地质背景下,婆罗洲拉让河和巴兰河为曾母盆地南部与文莱—沙巴盆地的主要物源,发育三角洲相、滨浅海相、浊积扇相、浅海相砂岩储层;同时,压扭型构造发育,不仅形成断块与背斜型油气藏,同时具有良好的油气运移条件。     

内蒙产高烧失低品位硅藻土的提纯及碳化性能

针对内蒙产高烧失低品位硅藻土的提纯,采用水洗[CD*2]焙烧工艺进行了实验。探索了水选次数、焙烧条件等对提纯效果的影响。采用XRD、FTIR、SEM、BET和化学分析等方法对提纯试验获得的产物进行了表征。结果表明:采用水选法可以实现石英、长石和黏土类杂质的去除,有机质的去除采用600 ℃焙烧就可以获得理想的提纯效果。提纯硅藻土SiO₂质量分数达到82.98%以上,比表面积可达44.5 m²/g,堆积体积达21 mL/10g。在隔绝空气条件下焙烧水选提纯土,获得的碳化硅藻土与橡胶相容性好,可替代半补强炭黑。     

An Overview on the Composition and Age of Upper Crust of Proto-Tethyan Lajishan Intra-oceanic Arc, NE Tibet Plateau

Identification and anatomy of oceanic arcs within ancient orogenic belt are significant for better understanding the tectonic framework and closure process of paleo-ocean basin. This article summarizes the geological, geochemical, and geochronological characteristics of upper crust of Proto-Tethyan Lajishan intra-oceanic arc and provides new data to constrain the subduction evolution of the South Qilian Ocean. The intra-oceanic arc volcanic rocks, including intermediate–mafic lava, breccia, tuff, and minor felsic rocks, are distributed along southern part of the Lajishan ophiolite belt. Geochemical and isotopic compositions indicate that the intermediate–mafic lava were originated from depleted mantle contaminated by sediment melts or hydrous fluids, whereas the felsic rocks were likely generated by partial melting of juvenile mafic crust in intra-oceanic arc setting. Zircons from felsic rocks yield consistent and concordant ages ranging from 506 to 523 Ma, suggesting these volcanic rocks represent the relicts of upper crust of the Cambrian intra-oceanic arc. Combined with the Cambrian forearc ophiolite and accretionary complex, we suggest that the Cambrian intra-oceanic arc in the Lajishan ophiolite belt is belonging to the intra-oceanic arc system which was generated by south-directed subduction in the South Qilian Ocean at a relatively short interval between approximately 530 and 480 Ma.