Palaeogeography and clay mineralogy of mid-Cretaceous flysches in the Gibraltar Arc area     

A. Lpez-Galindo  A. Martín-Algarra 《Cretaceous Research》1992,13(5-6)

A combined sedimentological and mineralogical study of several mid-Cretaceous sequences of the western Betic Cordillera and northern Rif has lead to the distinction of three main palaeogeographic areas. The basins of these areas received influxes of terrigenous sediments from different source areas. The southern Iberian margin was fed from the Iberian palaeocontinent and its clay-mineral association is characterized by a high content of well crystallized illite and kaolinite; the distal part of this margin was locally starved of continental sedimentation, but contains a considerable clayey contribution, probably oceanic in origin, made up mainly of smectites, illite and palygorskite. The sediments in the North African margin and the southern part of the North African Flysch Trough came from the African continent, the typical Aptian-Albian clay-mineral association being well crystallized illite, illite-smectite mixed layers, kaolinite, chlorite and lesser quantities of vermiculite. The terrigenous supply to the Mauritanian Realm of the North African Flysch Trough came from the Meso-Mediterranean terrane, and its usual Aptian-Albian clay association is illite, vermiculite, illite-smectite mixed layers and kaolinite. A significant change in the clay mineralogy occurred during the late Albian-early Cenomanian in the two former areas, consisting of a decrease in the detrital supply and a concomitant increase in smectites and palygorskite.The sedimentological and mineralogical evolution of this area was controlled by a combination of tectonic, eustatic and climatic changes in the westernmost Tethys during the mid-Cretaceous.  相似文献   

福建漳州复式岩体磁铁矿的成因矿物学特征   总被引：6，自引：0，他引：6  

严炳铨 《福建地质》1993,12(1):1-16

漳州花岗岩岩基共分两期七次(Ⅰ-Ⅶ)侵入,是中国东南沿海燕山晚期有代表性的大型复式岩体。笔者对区内各类花岗岩磁铁矿作了较深入的矿物学工作,包括晶出产状、晶体形态、X射线衍射、红外谱学、化学成分及稀土元素地球化学等方面的研究。本文重点论述磁铁矿的标型特征及成因意义,并提出区分不同成因花岗岩类岩石磁铁矿矿物学的判别标志,结合副矿物组合及岩石化学特点,对区内早、晚两期花岗岩类的成因分别判别为I型和A型花岗岩。  相似文献   

江华河路口黄玉的宝石学特征研究     

陈志强 《湖南地质》1993,12(2):98-101

本文介绍了研究区黄玉产出的地质环境及其颜色、形态、硬度、比重、折射率、多色性、包裹体、红外光谱、重量分布、可用率、加工方法等宝石学特征。  相似文献   

Differences of granitic weathering at the northern and southern feet of Dabie Mountains,Central China: Implication for tectonic and climatic environments   总被引：2，自引：0，他引：2  

续海金  马昌前  刘凡  杨坤光 《中国科学D辑(英文版)》2003,46(7):641-651

Previous studies of weathering generally started with geochemistry[1—8] and mineralogy[9—12], and have been focused on chemical weathering rates[1—3], removability-enrichment of elements[3—6] during chemical weathering, and the age of weathering profi…  相似文献   

纳米科技与粘土矿物学研究的思考   总被引：2，自引：0，他引：2  

杨献忠 《岩石矿物学杂志》2003,22(2):204-208

纳米科技已在地学领域取得了重要研究成果。粘土矿物学在材料科学中占有重要的地位,有必要建立“纳米粘土矿物学”这一学科,其研究手段与纳米科技一致,研究内容主要包括：纳米粘土矿物微粒矿物学、纳米粘土矿物体系物理学、纳米粘土矿物化学、纳米粘土矿物材料学和纳米粘土矿物加工学。本文进一步对纳米粘土矿物的检测方法和检测标准、聚合物／纳米粘土矿物复合材料的产业化提出了思考。  相似文献   

Paleohydrology of Andean saline lakes from sedimentological and isotopic records, Northwestern Argentina     

Blas Valero-Garcés  Antonio Delgado-Huertas  Norma Ratto  Ana Navas  Larry Edwards 《Journal of Paleolimnology》2000,24(3):343-359

The paleohydrological evolution of several high altitude, saline lakes located in the southernmost Altiplano (El Peinado and San Francisco basins, Catamarca province, NW Argentina) was reconstructed applying sedimentological, geochemical and isotopic techniques. Several playa lakes from the San Francisco basin (26° 56 S; 68° 08 W, 3800-3900 m a.s.l.) show evidence of a recent raise in the watertable that led to modern deposition of carbonate and diatomaceous muds. A 2 m - long core from El Peinado Lake (26° 29 59 S, 68°05 32 W, 3820 m a.s.l.) consists of calcitic crusts (unit 3), overlaid by an alternation of macrophyte-rich and travertine clast- rich, laminated muds (unit 2), and topped by travertine facies (unit 1). This sedimentary sequence illustrates a paleohydrological evolution from a subaerial exposure (unit 3) to a high lake stand (unit 2), and a subsequent smaller decrease in lake level (unit 1). The ¹³C_{organic matter}record also reflects the lake transgression between units 3 and 2. Although there is a general positive correlation between ¹⁸O_carbonate and salinity proxies (Na, Li and B content), the large data dispersion indicates that other factors besides evaporation effects control chemical and isotopic composition of lakewater. Consequently, the oxygen isotopic composition cannot be interpreted exclusively as an indicator of salinity or evaporation ratio. The degassing of CO₂ during groundwater discharge can explain the enriched ¹³C values for primary carbonates precipitated. The carbon budget in these high altitude, saline lakes seems to be controlled by physical rather than biological processes.The Altiplano saline lakes contain records of environmental and climatic change, although accurate ¹⁴C dating of these lacustrine sediments is hindered by the scarcity of terrestrial organic material, and the large reservoir effects. Sedimentologic evidence, a ²¹⁰Pb-based chronology, and a preliminary U/Th chronology indicate a very large reservoir effect in El Peinado, likely as a result of old groundwaters and large contributions of volcanic and geothermal ¹⁴C-free CO₂ to the lake system. Alternative chronologies are needed to place these paleorecords in a reliable chronological framework. A period of increased water balance in the San Francisco basin ended at about 1660 ± 82 yr B.P. (calendar yr U/Th age), and would correlates with the humid phase between 3000 and 1800 yr B.P detected in other sites of the southern Altiplano. Both, ²¹⁰Pb and preliminary U/Th dating favor a younger age for the paleohydrological changes in El Peinado. The arid period reflected by subaerial exposure and low lake levels in unit 3 would have ended with a large increase in effective moisture during the late 17th century. The increased lake level during deposition of unit 2 would represent the period between AD1650 - 1900, synchronous to the Little Ice Age. This chronological framework is coherent with other regional records that show an abrupt transition from more arid to more humid conditions in the early 17th century, and a change to modern conditions in the late 19th century. Although there are local differences, the Little Ice Age stands as a significant climatic event in the Andean Altiplano.  相似文献   

Mineralogical and geochemical study of a newly discovered mafic granulite, northwest China: Implications for tectonic evolution of the Altay Orogenic Belt   总被引：5，自引：0，他引：5  

Han-Lin  Chen  Zi-Long  Li  Shu-Feng  Yang  Chuan-Wan  Dong  Wen-Jiao  Xiao  Yoshiaki  Tainosho 《Island Arc》2006,15(1):210-222

Abstract A mafic granulite body was newly discovered in the Altay Orogenic Belt, northwest China. The rocks comprise a suite of coarse‐grained and fine‐grained granulites. Orthopyroxenes (hypersthenes) in the rocks have high X_Mg and low Al₂O₃ contents, whereas clinopyroxenes have low TiO₂ and Al₂O₃ contents. Amphiboles and biotites have a high Mg/(Mg + Fe²⁺) ratio and low contents of F and Cl. The peak metamorphic pressure–temperature (P–T) conditions are estimated as 750–780°C and 6–7 kbar, and retrograde P–T conditions are in the range of 590–620°C and 2.3–3.7 kbar, indicating significant decompression. Metamorphic reactions and P–T estimates define a clockwise P–T path. Geochemically, the rocks are high in Mg/(Mg + Fe) and Al₂O₃, depleted in U, Th, K and Rb, and characterized by light rare earth element enrichment and a weak positive Eu anomaly. The Altay mafic granulite shows depleted Nb, P and Ti contents in the mid‐oceanic ridge basalt normalized spider diagram. The geochemical characteristics suggest that the protolith of the Altay mafic granulite was calc‐alkaline basalt and andesite with an island‐arc affinity. The rock has a high ¹⁴³Nd/¹⁴⁴Nd ratio with ?Nd(0) > 0, indicating derivation from a mantle‐depleted source. In the present study, a two‐stage model for the evolution of the Altay mafic granulite is proposed: an early stage in which calc‐alkaline basalt and andesite with island‐arc affinity were subducted into a deeper level of the crust and subjected to granulite‐facies metamorphism generating the mafic granulite, followed by the later stage exhumation of the system into the upper crust by the late Paleozoic thrusting.  相似文献   

嫩江组二段底部标志层岩石矿物学特征与成片套损因素新认识   总被引：1，自引：0，他引：1  

刘合卓胜广  高合明刘建东吴恩成  金岩松 《地质论评》2006,52(4):532-538

大庆油田嫩江组二段底部与嫩江组一段顶部成片套损严重，从前一直认为泥岩吸水膨胀、蠕变是导致成片套损的主要因素。成片套损位置研究发现，嫩江组二段底部与嫩江组一段顶部成片套损实际集中于嫩江组二段底部标志层内，而嫩江组二段底部标志层岩石矿物学特征综合研究结果表明，其不含遇水膨胀的蒙脱石，且粘土矿物含量也低于其上下相邻岩石，表明其遇水膨胀与蠕变较弱，岩石遇水膨胀与蠕变不会构成成片套损的主要原因。嫩江组二段底部标志层岩石岩心观察描述、镜下鉴定、矿物成分综合测试和岩石强度性质研究发现，嫩江组二段底部标志层泥岩为富含长英质的质地坚硬岩石，含粘土矿物较少，不含蒙脱石，岩石吸水能力差、膨胀与蠕变能力弱；标志层中存在多个化石富集带，化石沿岩石层理分布形成沿层理方向的区域性力学薄弱面；沿化石层层理的抗张强度与抗剪强度远低于其他层位和垂直于层理方向的强度性质。因此，一旦注入水进入嫩江组二段底部标志层，富含化石的岩石沿岩石层理优先发生破坏，并迅速扩展，形成成片套损现象。  相似文献   

中太平洋WX海山富钴结壳磷酸盐矿物学研究及成因类型分析   总被引：2，自引：0，他引：2  

汪在聪李胜荣  刘鑫施娘华  初凤友佟景贵 《岩石矿物学杂志》2007,26(5):441-448

大洋富钴结壳普遍发生磷酸盐化,磷酸盐化对富钴结壳的各种属性存在显著影响,而磷酸盐的成因问题一直没有得到很好解决。中太平洋WX海山富钴结壳老壳层中发育着两期磷酸盐化事件所产生的上下两层磷酸盐,本文运用反光显微镜、扫描电子显微镜、电子探针、微量粉晶X衍射等手段分别对其进行了矿物学特征观察和测试,研究了老壳层上下两层磷酸盐特征并探讨其可能成因。上层磷酸盐由大量形态结构清楚的磷酸质有孔虫和超微化石以及非生物碳氟磷灰石(CFA)组成,成分均一,杂质少,表现出生物成因和原生自沉积特点;下层磷酸盐变化复杂,具有特征的交代结构,混杂较高的Si、Al、K、Fe成分,显示以磷酸盐交代碳酸盐成因为主。这表明不同磷酸盐化期形成的磷酸盐有不同的成因类型。  相似文献   

南京栖霞山铅-锌-银矿银的工艺矿物学研究     

蔡劲宏 《矿产与地质》2007,21(2):196-199

研究了南京栖霞山铅-锌-银矿银的工艺矿物学特征,分析了矿石的化学组成,对矿石中银矿物的种类、成份、粒度、嵌布特征进行测定和统计,并进行了矿石中银的物相分析和银的平衡配分。根据银的工艺矿物学研究结果,提出了提高银的选矿回收率的建议。  相似文献