新疆博格达-哈尔里克-带金矿类型及找矿方向研究

结合新疆博格达-哈尔里克一带金矿的成矿特点,将区内已发现的金矿划分为4个主要类型：韧性剪切带型金矿、火山热液型金矿、岩浆热液型金矿以及沉积型金矿。通过分析大地构造环境、地层建造、断裂构造、侵入岩及化探异常等因素对该地区金矿的控矿作用,总结区域金矿的成矿条件以及在时间和空间上的成矿规律和演化过程,指明各类型金矿的控矿因素以及找矿标志,为研究区今后的金矿勘查工作指明方向。     

Deep-seated structure and gold content of Russia and China contiguous territories

On the contiguous territories of southeastern Russia and northeastern China,many gold-bearing areas are conjugate in space with the gradient zones of the gravity field.Large gold-ore districts,defining in many respects the metallogenic signature of the region,are located on the joints of differently oriented gradient zones.In the best-studied districts,the Precambrian protrusions,staged distribution of magmatic chambers (by vertical) above the Mohorovicic discontinuity and restriction to the peripheral parts of intrusive massifs have been recognized.Different-type gold deposits in the studied ore-placer districts and nodes are often located on the areas of joint of the granitoid massifs and subvolcanic bodies with depressions.Availability of areals of metasomatic alterations of rocks,placers,and ore occurrences of precious metals on such but poorly studied areas can serve as the basis for the revision and detailed forecasting-prospecting works to develop the mineral-raw material base of the region for precious metals.     

Carboniferous coprolites from Qinhuangdao of North China

Here we reported the coprolites that are preserved in the dark grey silty shale of the Carboniferous Benxi Formation from Shimenzhai,Qinhuangdao,North China.The coprolites occur in a sinusoidal and ribbon-like aggregate.A coprolite granule is sesame-shaped,roundish at the terminals,equidimensional and equimorphic.It is 2.2 mm long and 0.6 mm wide.Its ventral surface appears flat,and its dorsal surface is slightly convex and has an axial furrow consisting of a string of bead-shaped pits.The coprolite granule has a directional arrangement and general equality in distribution within the aggregate.Its long axis is commonly perpendicular to the margins of the aggregate.The undigested food remains of animals and plants and the organomineral calcites with heteromorphology can be seen within the coprolite granule under photomicroscope and SEM.We deduced that a tracemaker of coprolites may be a tiny polyphagia animal similar to a modern loach or a tiny fish and that the tracemaker defecated and moved in synchronization below the interface between water and sediment.The coprolites may have a high viscidity and intensity while they were defecated.Diagenesis of feces may take place earlier and quicker than the host strata because of microbes.The lagersttte of coprolites described herein may result from the combination of many factors,such as the high content of oxygen in the Carboniferous atmosphere,the brackish lagoon in humid and tropic climate background,the low water energy,and the anoxic taphonomic environment that was lack of other animals.Further we suggested that the deoxidized color (dark grey) of host strata of coprolites may be formed in the sedimentary environment rich in oxygen and the early anoxic diagenetic environment.     

Ostracod fauna across the Permian-Triassic boundary at Chongyang, Hubei Province, and its implication for the process of the mass extinction

Thirty species of 10 ostracod genera were identified from 440 fossil specimens isolated through the hot acetolysis of the rock samples collected across the Permian-Triassic boundary at Chongyang section. Twenty species of 6 genera are found to occur in the limestone of Changxing Formation, and 11 species of 7 genera above the main faunal mass extinction horizon. The os-tracod assemblages identified at the Chongyang section are obviously different from those previously reported in the contem-poraneous microb...     

Eclogite-melt/peridotite reaction: Experimental constrains on the destruction mechanism of the North China Craton

To study the mechanism of melt-peridotite reaction pertinent to the destruction of the North China Craton (NCC) lithosphere, a series of experiments were performed at a pressure of 2.0 GPa and temperatures from 1250 to 1400°C using Bixiling eclogite and Damaping peridotite as starting materials. The experimental results show that the reaction between eclogite melt and peridotite causes dissolution of olivine and orthopyroxene and precipitation of clinopyroxene in the melt. The experimental run products, cha...     

北祁连西段石鸡河地区火山岩地球化学特征及其动力学意义

石鸡河一带是近年新发现的北祁连山多金属成矿带, 气侯和自然条件恶劣, 研究程度很低.该区地层岩性为阳起石岩、角岩和细碧岩; 岩石地球化学和Nd同位素数据显示岩石来源于亏损地幔, 具有N-MORB洋脊玄武岩特征; Sr同位素特征显示地层Sr同位素组成的改变是蚀变引起, 而不是由地壳物质加入引起的.Sm-Nd等时线年龄为481±20 Ma.提出了石鸡河地区地层形成于早奥陶世, 成岩环境为北祁连洋扩张环境, 而非区域资料上显示的残留海盆封闭、大陆碰撞造山环境.      

东秦岭金堆城花岗斑岩体的锆石U-Pb年龄、物质来源及成矿机制

通过LA-ICP-MS方法测得金堆城和老牛山花岗岩体中锆石U-Pb年龄分别为143.7±3 Ma和144.5±4.4 Ma,与金堆城钼矿床中辉钼矿的Re-Os年龄139±3.0 Ma在误差范围内一致,界定了金堆城成岩成矿时代为侏罗纪末-白垩纪初,2个岩体为同期岩浆事件的产物,与燕山运动有关.金堆城岩体较老牛山岩体富SiO₂、K₂O,岩石地球化学数据显示2个岩体都具有一致的高硅、富碱、过铝质系列和钙碱性岩石系列特征;高的ε_Sr(t)、低的ε_Nd(t)及Pb同位素图解证明2个岩体主要来自下地壳物质部分熔融,可能有少量地幔物质加入.年代学与岩石地球化学数据证实老牛山岩体和金堆城岩体的岩浆源区与岩石成因相同,推测老牛山岩体在深部发生分异演化,为金堆城小岩体提供了大量的热液和矿物质,从而出现了金堆城小岩体成大矿现象.      

太平洋海山钴结壳资源量估算

为合理地估算出太平洋海山钴结壳资源量, 基于我国西太平洋海山钴结壳拖网采样调查资料以及对太平洋海山钴结壳资源分布规律和钴结壳矿区圈定参数指标的深入研究, 创造性地按海山不同高度、不同洋壳年龄赋予不同结壳厚度, 进而首次计算出太平洋海山干结壳资源量为(507.06~1 014.11)×108 t, 锰为(111.15~222.29)×108 t, 钴为(3.04~6.08)×108 t, 镍为(2.23~4.46)×108 t, 铜为(0.66~1.32)×108 t, 结壳分布面积为2 062 862 km2.通过Co通量与结壳Co沉积量、结壳厚度的相关分析表明, 赋予不同洋壳年龄段的结壳厚度是理论厚度的6.10%~12.20%, 这与Ku et al.得出"结壳生长时间只占其整个生命史4%"的认识非常相近, 说明所赋结壳厚度基本合理, 得出的结壳资源量基本正确.为整个大洋海盆内海山钴结壳资源量的估算提供了新方法.      

赣西北蒙山岩体的锆石U-Pb-Hf、地球化学特征及成因

华南印支期花岗岩形成的构造背景和成因机制存在较大的争议,赣西北印支期岩浆活动的规模及该次岩浆活动是否与基性岩浆的底侵有关,仍缺乏可靠的资料.过去认为赣西北蒙山花岗岩形成于燕山期,而本次锆石LA-ICP-MS U-Pb年代学研究表明,蒙山3次花岗质岩浆活动的时间分别为236±3 Ma,220±3 Ma和217±1 Ma.蒙山花岗岩属准铝－过铝质,高硅、富钾,K₂O+Na₂O为7.53%~8.86%;稀土总量为213.09~380.75 μg/g,轻稀土元素富集,δEu=0.07~0.40,富集大离子亲石元素,Nb-Ta弱亏损,P、Ti亏损.大部分花岗岩的ε_Nd(t)值为-9.9~-6.1,Nd二阶段模式年龄t_DM2为1.5~1.8 Ga.第1次形成的灰白色粗粒花岗岩锆石的ε_Hf(t)值大部分集中在1.10~2.65,Hf同位素单阶段模式年龄t_DM1集中分布于782~866 Ma,二阶段模式年龄t_DM2集中分布在1 096~1 186 Ma,说明其物源主要为新元古代早期形成的地壳;第3次形成的细粒花岗岩锆石的ε_Hf(t)值集中分布于1.71~4.98,t_DM1为671~832 Ma,t_DM2集中在932~1 139 Ma.蒙山细粒花岗岩锆石的Hf同位素组成暗示成岩过程中有基性岩浆加入,为华南部分印支期花岗岩的成因与基性岩浆底侵有关的关系提供了证据.蒙山花岗岩的Nd同位素和锆石Hf同位素出现了解耦现象,解耦原因可能与花岗岩的物源主要为新元古代早期形成的具有Nd-Hf解耦特征的弧源地壳有关.根据目前获得的有关华南印支期火成岩的资料,总结了华南印支期花岗岩类岩石的成因类型及其时空分布规律,据此讨论了华南印支期的动力学背景和华南印支期花岗岩的成因机制,认为华南印支期的构造－岩浆活动与古太平洋西北向俯冲于华南板块之下有关.