伊利石单元粒子及其研究意义

单元粒子是单晶体构成的细小的粘土颗粒,是由一种或多种层状结构的硅酸盐构成的混层粘土的基本单元。多数伊利石单元粒子以混层晶体的"建筑砌块"的形式产出,"砌块"与"砌块"之间,在 a、b方向通过"砌块"的边缘界面相"砌合"而连接,在 c轴方向通过平面界面相"砌合"而连接。还对伊利石单元粒子的生长机理及形成过程中的形态变化、利用伊利石单元粒子的厚度划分成岩作用阶段等方面的研究成果进行了综述。伊利石单元粒子的形成过程有三个阶段：蒙脱石伊利石化过程中2nm厚的伊利石粒子的成核作用阶段、成核作用与生长作用阶段和表面控制生长阶段。伊利石单元粒子生长过程中,伊利石单元粒子呈现从板状体到条状体的生长,而板状颗粒又呈现各种螺旋生长图案,有圆形、残缺的圆形、多边螺旋、平行阶梯状螺旋、交错螺旋等。伊利石单元粒子的厚度分布服从对数正态型,其峰值为10.5nm。单元粒子与纳米科技两者的主要研究内容和所采用的方法基本一致,建议今后将研究单元粒子与研究纳米粘土矿物学有机地结合起来。     

川北阿坝地区三叠系粘土矿物特征及地质意义

分析了川北阿坝地区三叠系泥质岩的岩石矿物组合、粘土矿物类型、伊利石结晶度和镜质体反射率特征,并以此划分成岩演化阶段及变质程度。以成岩作用—极低级变质作用的研究方法,明确了阿坝地区成岩作用及极低级变质作用的上、下界限及区域分布规律:以唐克为中心的地区处于成岩作用晚期阶段,成岩作用温度200～212℃,伊利石结晶度IC≥0.42;周围地区处于极低级变质作用阶段,成岩作用温度212～222℃,伊利石结晶度IC<0.42。镜质体反射率(Ro)也具有同样的演化规律。对该地区域上成岩演化的差异及原因作如下解释:由于构造活动的远近程效应存在差异,该地区的周缘明显受到构造作用的影响,因叠加动力变质而达到极低级变质作用阶段;唐克位于阿坝地块中心,受构造作用的影响相对较小,因而处于成岩作用晚期阶段。     

云南小湾断层泥矿物特征及其构造意义

通过显微镜观察、X射线衍射、红外光谱和化学分析等方法研究云南小湾断层泥中伊利石矿物特征,结果显示:(1)断层泥中的伊利石发育定向排列,其集合体呈扭折褶皱变形,有时呈流状构造充填在碎屑之间;(2)伊利石的X射线衍射特征为△[(002)-(001)]>8°,Ir>1,BB₁<4°,属ISII有序混层,膨胀层约占15%,晶胞参数b₀=8.993Å,1M多型结构;(3)层间阳离子2Ca+Na+K≈1,MgO含量变化1.05%-2.89%,结晶水(H₂O⁺)含量变化4.43%-5.23%。综合上述特征认为,断层泥伊利石不同于其它成因的伊利石,它是断层活动的直接产物,因此,根据它的特征可以推测断层活动机制。     

New findings on the tectono-metamorphic history of the western Rhenish Massif (Germany) by K–Ar dating of metasedimentary illite

Metapelites, clay-rich sandstones and volcanics from Cambrian, Ordovician and Lower Devonian strata of the western Rhenish Massif underwent a complex regional Variscan tectono-thermal evolution, as shown by mineralogical and K–Ar isotopic analyses of the illite to mica components from three NW-SE transects. The metamorphic degree extended from an anchimetamorphic to an epimetamorphic intensity during two major episodes of illite crystallization at 328 ± 6 and 282 ± 12 Ma. A further late orogenic or post-orogenic extensional activity could also be detected, but not precisely, around 270 Ma, probably recorded by the precipitation of illite in new or reactivated extensional faults with upward moving heat flows.     

东南沿海早白垩世火山岩的极低级变质作用研究

中国东南沿海广泛分布的白垩纪火山岩中,发育一套具特殊岩相学特征的火山岩地层,以浙江高坞组和福建南园组为代表,其主体为熔结凝灰岩,以深灰色厚层致密块状、含大量长石和石英晶屑、大面积出露但假流动构造模糊为突出特征,而明显区别于其它白垩纪地层组的熔结凝灰岩,表明其具有独特的成岩过程。伊利石结晶度研究表明,高坞组和南园组火山岩特殊的岩相学特征与其成岩后受到极低级变质作用,从而发生一定程度重结晶有关,这一过程使其岩石结构构造趋于均一化。通过对上下火山岩系火山岩的伊利石结晶度、b0值及多型特征对比分析表明,东南沿海这一大范围的火山岩极低级变质作用,可能是早白垩世晚期"闽浙运动"后岩石圈发生强烈伸展,导致区域大规模热隆作用的反映,并与上下火山岩系之间区域性不整合面的形成、长乐-南澳构造带强烈的变质变形事件及东南沿海大规模金铜矿、非金属等成矿作用密切相关,具有重要的研究意义。     

内蒙古东北地区上古生界伊利石研究

内蒙古东北地区上古生界主要是一套泥质岩石,其详细深入的矿物学工作尚不多见.本文利用JSM-6700F场发射电镜及INCA能谱仪,探讨了伊利石在成岩.极低级变质作用过程中的行为.采用D/max-2500 X-射线衍射仪,研究了伊利石的结晶度、多型和b0值.伊利石结晶度变化于0.28～0.77,除去构造应力对伊利石结晶度指数值的影响,研究区伊利石结晶度指数应>0.34,反映晚古生代地层主体属于晚期成岩带和低级近变质带.伊利石(白云母)多型分三种类型,分别是1Md型、1Md+2M1混合型和2M1型,是晚期成岩带和低级近变质带的产物.伊利石(白云母)b0值变化于8.9892 ～9.0404 之间,b0平均值9.0196 ,属中压相.     

冈底斯成矿带陆相火山岩区浅成低温热液矿床蚀变分带模型——以西藏斯弄多矿床为例

斯弄多银铅锌矿床是冈底斯成矿带发现的首个低硫化浅成低温热液矿床。本文采用短波红外技术对矿区进行了精细蚀变矿物分带划分,并结合岩石地球化学测量对不同蚀变带元素的迁移机制进行了系统分析,构建了斯弄多矿区的短波红外勘查模型。研究发现:(1) Al-OH波长值的无序排列变化说明斯弄多矿床中存在不同岩浆热液流体的混合作用;(2)不同矿物组合形成了明显的蚀变分带,垂向上(由内向外)形成了绢云母化带→绢云母-钠云母-蒙脱石带→绢云母-伊利石-蒙脱石带→绢云母-伊利石带;(3)隐爆角砾岩型矿体中成矿元素Ag-Pb-Zn具有明显的分带性,其中,Ag主要赋存在绢云母-伊利石带,Pb-Zn则主要赋存在绢云母-伊利石-蒙脱石带;(4)热液脉型Ag-Pb-Zn矿体品位与伊利石结晶度指数IC关系密切,矿体主要赋存于0. 6≤IC≤1. 2的范畴;(5)以钻孔BZK0301(3号勘探线)为界,斯弄多矿床成矿性优劣存在一条明显界线,NE向由于不同流体的混合作用成矿性较好,SW向因为流体较为单一成矿性差。     

关于伊利石结晶度诸指数的评价

本文根据结晶学原理、Ｓｃｈｅｒｒｅｒ定律、Ｗａｒｒｅｎ－Ａｖｅｒｂａｃｈ理论和Ｘ射线衍射峰形态学原理提出任何衍射峰都是由五个基本要素组成的,即：衍射峰位置;最大衍射强度;半高宽;衍射峰形态和对称性。各衍射峰要素都具有其自身的物理学意义,其中,只有半高宽和衍射峰形态是与晶体内部结构和大小即结晶度相联系的。据此,分析评价了与Ｘ射线衍射相关的Ｋüｂｌｅｒ指数、Ｗｅｂｅｒ－ＤｕｎｏｙｅｒｄｅＳｅｇｏｎｚａｃ－Ｅｃｏｎｏｍｏｕ指数、Ｗｅａｖｅｒ指数、Ｍｉｌｉｅｒｓ指数、Ｗｅｂｅｒ指数、分解ＨＷ及纯Ｃ轴厚度等伊利石结晶度指数的理论基础、使用前提和条件、特点及误差源。指出Ｋüｂｌｅｒ指数、Ｗｅｂｅｒ－ＤｕｎｏｙｅｒｄｅＳｅｇｏｎｚａｃ－Ｅｃｏｎｏｍｏｕ指数和分解ＨＷ为非条件性单一结晶度指数;Ｗｅａｖｅｒ指数、Ｗｅｂｅｒ指数和高宽比为条件性单一结晶度指数;消除晶体内部微应变影响的ｃ轴厚度为全面描述伊利石结晶度指数;而Ｍｉｌｉｅｒｓ指数不可描述伊利石结晶度。     

Syn- and post-sedimentary controls on clay mineral assemblages in a tectonically active basin,Andean Argentinean foreland

In the northern part of the Calchaquí Valley (NW Argentina), Palaeogene Andean foreland sediments are represented by a 1400-metre-thick continental succession (QLC: Quebrada de Los Colorados Formation) consisting of claystones, siltstones, sandstones, and conglomerates representing sedimentation in fluvial-alluvial plains and alluvial fan settings. To understand the main syn- and postsedimentary variables controlling the clay mineral assemblages of this succession, we have studied the fine-grained clastic sediments by X-ray diffraction and electron microscopy, along with a detailed sedimentary facies analysis, for two representative sections. In the northern section, the whole succession was sampled and analysed by XRD, whereas in the second section, a control point 15 km to the south, only the basal levels were analysed. The XRD study revealed a strong contrast in clay mineral assemblages between these two sections as well as with sections in the central Calchaquí Valley studied previously. In the northernmost part of the study area, a complete evolution from smectite at the top to R3 illite/smectite mixed-layers plus authigenic kaolinite at the bottom, through R1-type mixed-layers in between, has been recognized, indicating the attainment of late diagenesis. In contrast, the clay mineral assemblages of equivalent foreland sediments cropping out only 15 km to the south contain abundant smectite and micas, subordinate kaolinite and chlorite, and no I/S mixed-layers to the bottom of the sequence. Early diagenetic conditions were also inferred in a previous study for equivalent sediments of the QLC Formation cropping out to the south, in the central Calchaquí Valley, as smectite occurs in basal strata. Burial depths of approximately 3000 m were estimated for the QLC Formation in the central and northern Calchaquí Valley; in addition, an intermediate to slightly low geothermal gradient can be considered likely for both areas as foreland basins are regarded as hypothermal basins. Consequently, the attainment of late diagenesis in the northernmost study area cannot be explained by significant differences in burial depth nor in geothermal gradient in relation to the section 15 km to the south nor with the central Calchaquí Valley. The formation of R3 mixed-layer I/S and authigenic kaolinite in the northern study area was most likely controlled by the circulation of hot, deep fluids along the reverse faults that bounded the Calchaquí valley. These faults were active during the Cenozoic, as evidenced by the syndepositional deformation features preserved in the studied sediments. Stress could also have been a driving force in burial diagenesis at the R3 mixed-layer I/S stage in these young continental sediments.     

K–Ar illite dating to constrain multiple events in shallow crustal rocks: Implications for the Late Phanerozoic evolution of NE Asia

A recently developed illite-age-analysis (IAA) approach was applied to determine the multiple events for the Chugaryeong fault belt, Korea. Each event was determined by a combined approach of the optimized illite-polytype quantification and the K–Ar age-dating of clay fractions separated from the fault clays. The Late Cretaceous to Paleogene events (76.5 ± 0.8, 69.1 ± 0.6, 59.3 ± 0.7, and 48.2 ± 0.7 Ma) were recognized by calculating the authigenic 1M/1M_d illite ages on the IAA plots of the fault clays. The Early Cretaceous ages (121.7–124.7 and 112.4 ± 1.5 Ma) were also obtained from the convergent intercepts of 100% 2M₁ illite on the IAA plots. The absence of the 2M₁ illites in the host-rock indicates that the Early Cretaceous ages represent the timings of high-T hydrothermal events of >280 °C. The 2M₁ illites in the fault clays should be pre-formed by a fluid-rock interaction under a relatively high-T subsurface condition, and be mechanically reworked into the near surface along the fault by post-tectonic events. This is the first report determining the absolute age constraints of multi-activated tectonic events from a fault. These geochronological determinations of the multiple events recorded in the Chugaryeong fault belt are crucial to establish the tectonic evolution of the Korean Peninsula since the Late Cretaceous.