植物群落生物量和有机碳对高寒草甸土地利用变化的响应

在中国科学院海北高寒草甸生态系统定位站地区,选择高寒矮嵩草草甸及其开垦后形成的农田和一年生人工草地作为研究对象,研究了高寒草甸不同土地利用方式下生物量和植物-土壤系统固定的有机碳量的变化。结果表明：3种土地利用方式相比较,地上生物量由高到低依次为人工草地〉农田〉高寒草甸（P〈0.01）,分别为11.83、9.78和4.36 t/hm~2;3种土地利用方式下地下生物量剖面分布均呈倒金字塔形,0～40 cm地下生物量为高寒草甸〉人工草地〉农田（P〈0.01）,分别为15.74、5.61和1.24 t/hm~2。随着高寒草甸土地利用方式改变,植物群落碳素固定量也随之减小,其序列由高到低依次为：高寒草甸〉人工草地〉农田（P〈0.05）,其值分别为7.63、6.81和4.51 t/hm~2。

江河源区不同建植年限人工草地土壤微生物及酶活性研究

对江河源区不同建植年限人工草地(2龄、4龄、6龄)土壤养分、微生物数量及酶活性进行研究.结果表明:不同建植年限人工草地土壤养分随着建植年限的增加呈"V"型规律变化,其中人工2龄草地土壤养分含量最高,6龄草地土壤养分含量虽不及2龄草地高,但均明显高于4龄草地.土壤细菌和放线菌数量与土壤养分变化规律一致,真菌数量随建植年限的增加呈降低趋势,土壤脲酶、过氧化氢酶和中性磷酸酶活性与细菌、放线菌和土壤养分变化规律相同.同时,土壤养分、微生物数量和酶活性变化均具有明显的空间层次现象,即随土层的加深呈降低的趋势.经典型相关分析表明,土壤细菌与土壤有机质、全氮、速效钾和pH值之间相关性最好,脲酶和过氧化氢酶活性与土壤有机质、全氮、速效氮、速效钾和pH值之间相关性最好,故土壤微生物数量和酶活性可作为评价土壤肥力的指标.

短穗兔耳草的克隆生长特征

以调查统计的方法研究了高寒草甸匍匐茎植物短穗兔耳草Lagotis brachystachya无性系的生长特征、形态特征以及能量分配规律,研究结果表明:匍匐茎只有1条的短穗兔耳草最多,占60.47%,匍匐茎有4条的短穗兔耳草只占6.98%.在牧草生长盛期,短穗兔耳草无性系的基株高度4.03cm,根长为9.11 cm,叶数为7.98;分株高度0.85 cm,根长2.73 cm,叶数为3.08;匍匐茎的茎生叶数为12.54,长度为15.14 cm,匍匐茎比节间重为2.18 mg/cm,粗度为0.97 mm,不同构件的干质量呈现出基株＞匍匐茎＞分株＞茎生叶的规律.随着匍匐茎数目的增多,短穗兔耳草无性系的基株根长逐渐增加,用于克隆繁殖的能量投资也有增加的趋势,其他参数都没有明显的变化规律.

海北高寒草甸地区能量平衡特征

以微气候观测为基础，研究晴天状况下海北高寒草甸地区净辐射通量、土壤热通量、感热通量和潜热通量变化等特征。结果表明：（1）该地区总辐射的水平较高，2000年4～10月达4227.049W·m~(-1)，地表反射率在4～10月平均为0.23，在植物生长盛期的5～9月为0.22。（2）正向净辐射约占天空总辐射的56%左右；一日间土壤热通量、感热通量和潜热通量所占净辐射通量的比例在不同季节变化差异较大，在所选择的6月到9月的4个晴天个例状况平均分别所占的比例为28.6%、68.0%和3.4%，表现出潜热通量在净辐射能量的分配中所占比例较大，感热通量次之，土壤热通量则很小。（3）各通量所通过零点的时间基本一致，一般在日出后的7：00和日落前的19：00。

黄头鹡鸰产卵能学的研究

在自然生长状态下 ,用测定在黄头鹡鸰(Motacillacitreola)成鸟产卵期性腺及输卵管蛋的质量变化的方法 ,研究了它们在产卵期间的能量投入及其分配形式 .产卵期 ,雌鸟用于性腺增长和卵形成的能量预算为 6 6 2 4～71 19kJ ,其中用于蛋白质和脂肪的能量分别为 40 42kJ和 2 5 82～ 30 78kJ,占总能量预算的 5 6 8%～ 6 1 0 %和36 3%～ 46 5 % .用于繁殖蛋白的能量分配为 :输卵管 2 77kJ ,卵黄蛋白 12 80kJ ,卵白蛋白 2 4 85kJ.雌鸟耗能最大的是第 0d～ +1d ,达 (13 2 8～ 14 2 6 )kJ/d .产卵期雄鸟耗能 (用于性腺增长 ) 7 98kJ,雌雄亲鸟用于卵的形成和性腺增长共投入能量 74 2 2～ 79 17kJ.雌鸟耗能为雄鸟的 8 3倍～ 8 9倍。

青藏高原东北部植物染色体数目和多倍性研究

对青藏高原东北部高山冰缘地区和相邻低海拔地区５９种多年生草本被子植物进行了染色体计数。其中，４５个种的染色体记数为首次报道，并确定其信性．对分布于高山冰缘地区和冰缘以下不同海拔地区植物染色体的多倍性进行分析研究，结果如下：（１）多年生草本被子植物多倍体频率随海拔高度上升而增加：海拔2000－3000ｍ，多倍体频率为29.4％－47.1％．3000－3800（4000）m（高寒灌丛－草甸区），多倍体频率为33.3％－53.3％；4000－5200ｍ以上的高山冰缘地区，多倍体频率达55.6％－70.4％．（２）高山冰缘地区新多倍体较多，并且与青藏高原上特有的植物类群（特有属、亚属或特有种）相关联。（３）分布在冰缘地区的多倍体广布种，通常都是较原始类群的古多倍体，它们可能在青藏高原强烈隆升以前就已经形成，并分化出许多生态型，在高原强烈隆升并出现高山冰缘环境以后，某些生态型突出繁殖适应机制（r型选择机制），能开拓新生境而在新出现的严酷而不稳定的冰缘地区繁衍，其它一些生态型则依靠营养生长优势（K型选择机制）广泛分布在其稳定、成熟的生境中。（4）冰缘以下地区的多倍体特有种多数属于古多倍体或次生多倍体。它们多数可能是由西南山地或秦岭、华北森林区系产生，然后扩散至青藏高原边缘。

Distribution and species diversity of plant communities along transect on the Northeastern Tibetan plateau

The distribution and species diversity of plant communities along a 600 km transect through the northeastern Tibetan Plateau (32 degrees 42'-35 degrees 07' N, 101 degrees 02'-97 degrees 38' E) with altitudes from 3255 to 4460 m are described. The transect started from the Youyi Bridge of Banma through Dari, Maqin and Maduo to Zaling Lake. The data from 47 plots along the transect are summarized and analyzed. The mean annual temperature, the mean annual rainfall and the length of growing season decreases from 2.6 to -4.5 degrees C, from 767.2 to 240.1 mm, from 210 to 140 days, respectively, along the transect from the southeastern Banma to northwestern Zaling Lake. The number of vascular plant species recorded in 47 plots is 242 including 2 tree, 34 shrub, 206 herb species. Main vegetation types on the transect from southeast to northwest are: Sabina convallium forest, Picea likiangensis forest, Pyracantha fortuneana + Spiraea alpina shrub, Hippophae neurocarpu shrub, Sibiraea angustata + Polygonum viviparum shrub, Stellera chamaejasme herb meadow, Potentilla fruticosa + Salix obscura + Carex sp. Shrub, Kobresia capillifolia meadow, P. froticosa + Kobresia humilis shrub, Caragana jubata + S. obscura shrub, Kobresia tibetica meadow, Kobresia pygmaea meadow, K. pygmaea + Stipa purpurea steppe meadow, Stipa purpurea steppe. Plant richness and diversity index all showed a decreasing trend with increasing of elevation along transect from southeast to northwest. Detailed information on altitudinal ranges and distribution of the alpine vegetation, vascular flora and environments over the alpine zone at northeastern Tibetan Plateau provides baseline records relevant to future assessment of probable effects of global climate changes.

非完整系统鲁棒控制方法及在水面移动机器人中的应用

近年来，随着机器人技术的发展，各种各样的移动机器人系统正在开始应用于工业、国防安全、公共安全、灾难救援、科学探测等领域；但是，遥控作业仍然是制约移动机器人广泛应用的一个核心问题。如何使机器人系统摆脱遥控的束缚而具有全自主行为能力，是目前机器人学领域重点研究的关键问题之一。自主环境适应能力是移动机器人最基本的自主能力之一。机器人系统需要面对不可预知的、动态的、存在时变扰动和噪声的工作环境，这通常会导致机器人动力学参数的变化，从而使传统的机器人控制技术很难得到满意的控制效果并达到自主环境适应的目的。同时，目前的移动机器人系统大都受非完整约束的影响，由于其约束的不可积性，使其控制与规划变得异常困难，因此研究移动机器人在存在不确定情况下的鲁棒控制问题，以及存在非完整约束条件下的镇定问题和规划问题具有非常重要的理论意义和实际应用价值。本文以沈阳自动化所与大连理工大学联合研制的三体船型水面移动机器人（UTV）这个典型的受不确定以及非完整约束影响的系统为背景，研究其在存在大量不确定因素及外界环境干扰条件下的鲁棒控制问题和其在受制于非完整约束情况下的镇定和运动规划问题，其中前者主要针对系统在受风、流、浪等外界干扰下的鲁棒控制问题；后者旨在解决满足非完整约束条件下的非线性系统规划与控制问题。本论文的具体内容安排如下：第1章，简单介绍了非完整系统的概念，归纳出非完整系统在控制上的两方面核心问题，即：不确定性及扰动的抑制问题和运动规划与控制问题。对解决这两类问题的现有方法进行了深入分析和综述，包括动态模型的在线估计共性方法、非完整约束系统运动控制方法、以及优化与预测控制方法，同时，介绍了本文作为仿真与实验对象的三体船型水面平台的发展概况。针对现有方法存在的问题有针对性地提出了本论文的研究内容。第2章，首先简要介绍了机器人学国家重点实验室与大连理工大学联合研制的三体船型水面移动机器人试验平台，作为本论文后续仿真与实验研究的对象，介绍了该平台的动力系统与控制系统。从运动控制的角度出发，综合考虑推力、水动力等对整个系统的动力学进行了分析，建立了完整的6自由度动力学模型以及水平面运动的简化模型。在此基础上，分析了三体船型水面移动机器人的非完整约束特性和能控性，为后续方法研究奠定了基础。第3章，提出了一种基于主动建模的鲁棒控制设计方法。对于包含难以准确建模动力学以及外来扰动等不确定性的系统，可以将其动力学模型合理简化，而将所有不确定因素以模型差的形式引入到系统中；将引入的模型差与系统原有状态组合成增广状态，构造出联合估计模型；再利用在线估计方法实时估计这个模型差；同时，将估计出的模型差利用某种控制策略反馈到控制量中，达到增强系统鲁棒性的目的。针对三体船型水面移动机器人，在理论上分析了上述方法的稳定性，并在实际三体船型水面机器人上开展了实验比较研究。实验结果表明此方法对系统中存在的各种不确定因素具有很好的抑制作用。第4章，重点研究非线性系统在线估计以及将在线与控制相结合的问题。在简要介绍可以用于非线性估计的UKF方法的基础上，针对其性能严重依赖噪声先验知识的问题，提出了一种基于主从结构的自适应滤波器设计方法。同时针对三体船型水面机器人非线性系统模型中存在的不确定性因素，提出了一种基于自适应UKF的指数跟踪控制器设计方法。仿真结果验证了自适应UKF算法的性能提高，同时验证了基于在线估计的指数跟踪控制器对时变参数与扰动的抑制作用。第5章，研究了非完整约束系统的镇定控制问题。提出了一种高维流形嵌入法；通过把二阶非完整约束系统嵌入到高维流形中，将在原空间中镇定到一个点的问题转化成在扩展的状态空间中镇定到一个子流形的问题；从而，可以将原空间不可连续反馈镇定的控制问题转化为高维流形中可连续反馈镇定控制问题，理论上证明了该方法的正确性和完备性。针对三体船型水面移动机器人的仿真结果验证了该方法的正确性。第6章，针对非完整约束对移动机器人可执行轨迹的制约问题，提出了跟踪控制Lyapunov函数的概念，并将其引入到非完整系统地运动规划中，用跟踪控制Lyapunov函数来保证规划算法的收敛性和可执行性。该方法将非线性预测控制与基于跟踪控制Lyapunov函数的广义逐点最小范数控制相结合，得到了一种在保证闭环稳定性前提下的运动规划算法；理论上证明了该方法的正确性，并针对三体船型水面移动机器人动力学进行仿真验证。

意大利的人工智能研究

中国科学院赴意大利人工智能访问小组一行四人于八二年九月访问了意大利的有关学术单位和高等学校。本文就这次访问了解到的有参考价值的内容作一概括介绍。

俯冲带深部流体特征——以西南天山变质俯冲杂岩为例

The subduction zone is an important site of the fluid activity and recycling of chemical elements. The fluid characteristic of deep subduction zones is a top scientific problem attracting the petrologists, geochemists and tectonists. In this dissertation, the characteristics of fluid activity within a deep subduction zone have been explored on the basis of the studies on the petrography, mineral chemistry, fluid inclusions, geochemistry and metamorphic P–T conditions of the omphacite-bearing high-pressure veins and related hosts from the low-temperature/high-pressure metamorphic belt in southwestern Tianshan, China. Multiple high-pressure veins are exposed in host eclogites and blueschists. The veins are composed predominantly of omphacite, garnet, quartz, and other minerals. Some veins contain cm-sized rutiles. In general, the vein can be divided into three types, the ‘in situ dehydration’ vein, the ‘external transport’ vein and the ‘composite’ vein. The omphacites within the veins and related host rocks contain lots of two-phase or three-phase primary fluid inclusions. The final melting temperature (Tfm) of fluid inclusions varies mainly from -0.6 to -4.3 °C, the homogeneous temperature (Th) varies from 185 to 251 °C, the salinity varies from 1.1 to 6.9 wt.% NaCl equivalent and the density varies from 0.81 to 0.9 g/cm3. The fluids were released under the conditions of T = 520–580°C and P = 15–19 kbar at blueschist facies to eclogite facies transition. The fluids include not only Li, Be, LILE, La, Pb-enriched and HFSE- and HREE-depleted aqueous fluids but also HFSE (Ti-Nb-Ta)-rich aqueous fluids. The complex composed of aluminosilicate polymers and F was the catalyst which had caused the Ti-Nb-Ta to be dissolved into the fluids. During the transport of the LILE-rich and HFSE- and HREE-poor fluids, they can exchange some chemical elements with country rocks and leach some trace elements in some extent. The rutile could be precipitated from the HFSE (Ti-Nb-Ta)-rich aqueous fluids when CO2 was added into the fluids. The host rocks could obtain some elements, such as Ca, Cs, Rb, Ba and Th, from the external fluids. The fluids with complex composition had been released within the deep subduction zone (>50 km) in Early Carboniferous during the subduction of the South Tianshan Ocean under the Yili–Central Tianshan Plate. The results obtained in this dissertation have made new progress compared with the published data (e.g. Tatsumi, 1989; Becker et al., 1999; Scambelluri and Philippot, 2001; Manning, 2004; Hermann et al., 2006; Spandler and Hermann, 2006).

青藏高原横波速度与各向异性结构及其壳幔形变印迹

As the most spectacular and youngest case of continental collision on the Earth, to investigate the crust and mantle of Tibetan plateau, and then to reveal its characters of structure and deformation, are most important to understand its deformation mechanism and deep process. A great number of surface wave data were initially collected from events occurred between 1980 and 2002, which were recorded by 13 broadband digital stations in Eurasia and India. Up to 1,525 source-station Rayleigh waveforms and 1,464 Love wave trains were analysed to obtain group velocity dispersions, accompanying with the detail and quantitative assessment of the fitness of the classic Ray Theory, errors from focal and measurements. Assuming the model region covered by a mesh of 2ox2o-sized grid-cells, we have used the damped least-squares approach and the SVD to carry out tomographic inversion, SV- and SH-wave velocity images of the crust and upper mantle beneath the Tibetan Plateau and surroundings are obtained, and then the radial anisotropy is computed from the Love-Rayleigh discrepancy. The main results demonstrate that follows, a) The Moho beneath the Tibetan Plateau presents an undulating shape that lies between 65 and 74 km, and a clear correlation between the elevations of the plateau and the Moho topography suggests that at least a great part of the highly raised plateau is isostatically compensated. b) The lithospheric root presents a depth that can be substantiated at ~140 km (Qiangtang Block) and exceptionally at ~180 km (Lhasa Block), and exhibits laterally varying fast velocity between 4.6 and 4.7 km/s, even ~4.8 km/s under northern Lhasa Block and Qiangtang Block, which may be correlated with the presence of a shield-like upper mantle beneath the Tibetan Plateau and therefore looked as one of the geophysical tests confirming the underthrusting of India, whose leading edge might have exceeded the Bangong-Nujiang Suture, even the Jinsha Suture. c) The asthenosphere is depicted by a low velocity channel at depths between 140 and 220 km with negative velocity gradient and velocities as low as 4.2 km/s; d) Areas in which transverse radial anisotropy is in excess of ~4% and 6% on the average anisotropy are found in the crust and upper mantle underlying most of the Plateau, and up to 8% in some places. The strength, spatial configuration and sign of radial anisotropy seem to indicate the existence of a regime of horizontal compressive forces in the frame of the convergent orogen at the same time that laterally varying lithospheric rheology and a differential movement as regards the compressive driving forces. e) Slow-velocity anomalies of 12% or more in southern Tibet and the eastern edge of the Plateau support the idea of a mechanically weak middle-to-lower crust and the existence of crustal flow in Tibet.

东北四海龙湾玛珥湖啊1500年来长链烯酮不饱和度温标与古水温重建

The alkenone unsaturation paleothermometer is an important proxy to reconstruct water temperature, and is widely applied to reconstructing sea surface temperature in most oceanographic settings. Recent research indicates that long chain alkenone is preserved in lacustrine sediments, and the alkenone unsaturation has good relationship with mean annual temperature in studied lakes. Thus, the alkenone unsaturation could be used as a temperature proxy to reconstruct temperature in limnic systems. In this study, we analyzed long chain alkenone from the varved sediments in Lake Sihailongwan, northeastern China. Based on the counting varves, we established time scale during the past 1500 years. The distribution pattern in the sediment is similar with the previous study in lacustrine environment. The ratio of C37:4 methyl ketone to the sum of C37 alkenones is high. Based on the published temperature- alkenone unsaturation equation, we reconstructed the mean air temperature and July water temperature during the past 1500 years. Three major cold periods are in AD560-950, AD 1540-1600 and AD1800-1920. Three major warm periods are AD450-550, AD 950-1400 and AD 1600-1800. The Medieval Warm Period was a significant warm periods. However, the traditional “Little Ice Age” was not a persistent cold period, and interrupted by relative longer warm period. The temperature variations in this study show a general similar pattern with the summer temperature reconstruction from Shihua Cave and the winter temperature from historical documents. The temperature variations from long chain alknone record show a good agreement with solar activity (10Be data from ice core and sunspot number from tree rings). It may suggest that solar activity is most important forcing in the studied area.

特提斯喜马拉雅带晚白垩世-始新世沉积源区分析及其构造意义

Tethyan Himalayan Sequence (THS) is located at the frontier of the India-Asia collision zone, which can preserve critical information about collision. This paper reports detailed petrology, geochemistry, spinels electron microprobe data, and in situ U-Pb ages and Lu-Hf isotopic data on detrital zircons from the late Cretaceous to early Eocene strata in Gyantze and Gamba area, south Tibet that provide important constraints on the early tectonic evolution of the India-Asia collision. In Gyantze, the lithic arkose in Zongzhuo mélange is characterized by, SiO2 =80.4%, Al2O3=8.6%, Na2O=1.6%, K2O=1.1%, LaN/YbN=8.90, and εNd (0) =-10.27. Spinels compositions are characterized by low TiO2 (generally <0.1%) and a Cr number mainly between 70 and 80. The largest population of detrital zircons is within the 73-169Ma range with high εHf (t) and > 500 Ma with complex εHf (t) values. The lithic arkose in Rilang conglomerate is characterized by, SiO2 =56.5%, Al2O3=15.6%, Na2O=4.7%, K2O=0.6%, LaN/YbN=5.00-5.29, and εNd (0) =1.92. Spinels of 2006T98 display high TiO2 (generally >0.2%) and a Cr number mainly between 70 and 85, other spinels are characterized by low TiO2 (generally <0.2%) and a Cr number mainly between 60 and 90. The largest population of detrital zircons is within 90-146 Ma range with high εHf (t). The lithic arkose in Jiachala formation is characterized by, SiO2 =64.6%, Al2O3=12.1%, Na2O=1.9%, K2O=1.8%, LaN/YbN=7.73-9.13, and εNd (0) =-5.52~-8.43. Spinels in the Jiachala formation have low TiO2 (generally <0.2%) and a Cr number between 39 and 88. Detrital zircons have a wide range of age distribution of 82-3165Ma with complex εHf (t). In Gamba, The quartze sandstone in Jidula formation is characterized by, SiO2=97.4%, Al2O3=0.9%, Na2O=0.03%, K2O=0.18%, LaN/YbN=18.70-21.684, and εNd (0) between -13.1~-7.4. While the lithic arkose in Zhepure formation is characterized by, SiO2=68.4%, Al2O3=7.3%, Na2O=1.15%, K2O=0.52%, LaN/YbN=6.09-8.99, and εNd(0)=-5.8~-6.3. Based on our geochemical analysis, spinles electron microprobe data, U–Pb ages and Hf isotope data for detrital zircons of the late Cretaceous-Eocene strata in Gyantze and Gamba, southern Tibet, the following major conclusions can be drawn: 1. In Gyantze, the Zongzhuo mélange was mainly derived from accretionary prism/THS of continental slop and Gangdese arc. Rilang conglomerate was totally from Gangdese arc. The Jiachala formation was derived from THS, suture zone and Gangdese arc. 2. In Gamba, the Jidula formation was from India craton, while the Zhepure formation was derived from THS, suture zone and Gangdese arc. 3. The deposite of Zongzhuo mélange and Rilang conglomerate (73-55Ma) marks the collision between India and Asia. 4. Late Paleocene-Eocene tectonic evolution is consistent with foreland basin system.

北祁连与块状硫化物矿床有关的早古生代火山岩的地球化学研究

Different conclusions from previous work are made from the geochemical study for the early Paleozoic volcanic rocks hosting massive sulfide deposits in the north Qilian Orogen. The main points are: (1)The geochemical characteristics of the basalts and rhyolites from the Baiyin deposit are not consistent with that of the volcanic rocks in the continental rift setting, but show the relationship with subduction. The basalts and rhyolites from the Baiyin deposit are probably individual tectonic slice piled by subduction, and there is no bimodal volcanic rock suite occurred in the Baiyin deposit. Zircon U-Pb dating constrains the magmatic emplacement of basalts and rhyolites at 475±10Ma and 453±12Ma, respectively. The basalts are characterized by enriched Th and Sr, and depleted Nb, Ta and Ti. They have relatively high Th/Nb ratios between 0.9 and 1.3. Their εNd(T) values vary from -1.2 to +3.4. The chemical and isotopic compositions display a typical subduction-related signature, and they suggest that an enriched component with the isotopic composition of EMII might have contributed to the generation of the Baiyin basalts. The basalts were likely formed in a mature island-arc or a volcanic arc built on comparatively young or thin continental crust in an active continental margin. The rhyoIites have low concentrations of LILE compared to the basalts. They do not seen to have a relationship with the basalts, because of their significantly higher εNd(T) values (+4.3～+7.7). The high and positive εNd(T) values also rule out their derivation from anatexis of the continental crust. A modeling study suggests that the source.of the Zhe-Huo and Xiaotieshan rhyolites is similar to boninite and IAT (island-arc tholeiite), and hence indicating an intra-oceanic arc environment. (2) The formation of the Shangliugou volcanic rocks from .Qilian area is also related to subduction. The basaltic andesite have low TiO_2(0.45～0.63%) and P_2O_5(0.04～0.09) content, and high Th/Nb ratios (0.3～0.6). They show flat REE patterns. Their εNd(T) values vary in a narrow range from +4.8 to +6.4. The chemical and isotopic compositions indicate that they are derived from a slightly depleted mantle source and are fromed in intra-island arc setting. The rhyolites show calc-alkaline trend. They show enriched LREE and fiat HREE patterns with obvious negative Eu anomaly. They have high Th/Ta ratios (5.0 ～ 11.7) and large negative εNd(T) values (-2.6 ～ -8.4). The rhyolites are formed in active continental margin and result from a mixed process of two endmembers, or crust assimilation. (3) The metal elements of the volcanic-hosted massive sulfide deposit have two sources, the copper and zinc are derived from rhyolitic magmas whereas the lead are probably related to old sediments overlying the rhyolites. (4) It is suggested here that the volcanic rocks hosting massive sulfide deposit in the north Qilian orogen, which are previously considered as a bimodal suite of Neo-proterozoic to middle Cambrian age in a continental rift, are virtually related to subduction magmatism in Ordovician age, and there might have no continental rift magmatism of Neo-proterozoic to middle Cambrian in the north Qilian.

安多地区早中侏罗世岩浆岩岩石地球化学和同位素年代学研究及其对构造演化的制约

Anduo area is located in the Central Tibet, the middle segment of the Bangonghu-Nujiang suture. Anduo Block is the northern part of Lhasa terrane. The relationships among the different geological bodies were determined during the 1: 250000 regional geological surveying. Petrography, petrologic geochemistry, isotopic geochemistry and geochronology of igneous rocks from the suture and granitoids from Anduo Block were analyzed systematically as a whole for the first time. Then, their tectonic setting and history are discussed.Anduo ophiolitic melange consists of metamorphic peridotites, cumulates, plagiogranites, sheeted dykes swarm, pillow lava and radiolarian cherts. The concentration of Cr and Ni in the metamorphic peridotites is very high, with Mg# about 0.94 ~ 0.97, higher 87Sr/86Sr and Pb isotopic ratios, and lower 143Nd/i44Nd ratio. LREE is enriched relative to HREE and positive Eu anomaly is very clear. The REE distribution curve is U shape. Nb and Ta anomalies from cumulate gabbro and sheeted dyke swarm are not clear, while that are slightly negative from pillow lava. Plagiogranite belongs to strong calc-alkaline series with high Si, middle Al, low Fe, Mg and low K contents. Eu anomaly (~ 1.23) from plagiogranites is slightly positive. The character of all components of ophiolite is similar to that of the MORB, while to some extent the ophiolite was influenced by crustal material. Anduo ophiolite formed in a mature back-arc basin. Additionally, intermediate acidity volcanic rocks within Anduo phiolite melange are island arc calc-alkline rocks related to ocean subduction.The early-middle Jurassic plutonic rocks are tonalite, granodiorite bearing-phenocryst, magaporphyritic hornblende monzogranite, magaporphyritic monzogranite, monzogranite bearing-phenocryst and syenogranite in turn. They belong to calc-alkaline series which developed from middle K to high K series temporally. REE distribution curves of all plutonic rocks are similar and parallel to each other. SREE and negative Eu anomaly values decrease. In the multi-element spider diagram, the curves of different plutons are similar to each other, but troughs of Nb, Sr, P and Ti from young plutons become more evident. This suggests that thereare some closely petrogenetic affinities among plutonic rocks which make up amagma plutonism cycle of the early-middle Jurassic. Magma source is mainly crustal,but abundant mafic microgranular enclaves within granitoids indicate that crastalmagma should be mixed with mantle-derived magma and the mantle-derived magmadecreased subsequently. Tonalite has features of I-type granite, magaporphyriticmonzogranite is transition type, and monzogranite bearing-phenocryst is S-typegranite. The characteristic of granitoids from Anduo Block suggest that the formingtectonic setting is active continental margin.Reliable zircon U-Pb SHRIMP ages are obtained in the study area firstly. Plagiogranite from the Anduo ophiolite of the Bangonghu-Nujiang suture is 175.1 Ma, and granitoids from Anduo Block is 172.6-185.4 Ma. Additionally, plagioclase from the plagiogranite dates a 40Ar/39Ar age of 144 Ma, while biotite and hornblend from granitoids of Anduo Block give a 163-165 Ma.Similar cooling ages of plagiogranite from the Anduo ophiolitic melange and granitoids from Anduo Block and the spatial distribution of the ophiolitic rocks between Anduo, Naqu, and Shainzha area suggest that bilateral subduction of the Bangonghu-Nujiang oceanic basin took place in the early-middle Jurassic. During this subduction, Anduo ophiolitic rocks were related to north subduction of the Bangonghu-Nujiang oceanic basin and Anduo back-arc basin spreading, while granitoids from Anduo Block were related to south subduction.