火山岩

All the volcanic rocks present younger K-Ar age (less than 5Ma), which can be termed as Cenozoic rocks. In general speaking, volcansim can be dividied into two eruptive stages. In the first stage, volcanic rocks for Pliocene epoch (4. 4-5Ma) consist of basanite and tephrite, which distributed on Mt. Crater, Cape Bird, and southern bank of Bonney Lake; In the second stage, volcanic rocks for Quaternary (less than 1 Ma) are mainly composed of latite, which are distributed on Cape Rodeys and Cape Evens.On the basis of geochemical data such as major elements, trace elements , rare earth elements, isotope, microprobe analysis, combined with main achievement taken by previous researcher in this area, conclusions are drawn basically as follows

所喷发的火山岩K-Ar年龄值均小于5Ma，为新生代火山岩，大体上可以分为两个喷发阶段，第一个阶段为上新世火山岩(年龄值为4.4-5.0Ma)，主要由碧玄岩和碱玄岩组成，分布于罗斯岛上的克雷克特山、鸟角和泰勒谷的博尼湖南岸；第二阶段为第四纪火山岩(年龄值均小于1Ma)，主要由安粗岩组成，分布于罗斯岛上的罗德角和伊万思角，通过主要元素、微量元素、同位素结合电子探针以及前人的研究成果，我们大体上可以得出如下认识

A good many mico-landblock of the early Neoproterozoic-Cambrian volcanic rock that distribute in the Tianshan orogenic belt and on its both sides, and the Carboniferous-Permian volcanic rocks that widely distribute in the Tianshan and adjacent regions are selected for subject investigating in this paper. Renewing the ocean-land format and ocean-land conversion process of Tianshan orogenic belt in the Paleozoic is the masterstroke for this paper. On the basis of detailed field investigation, many subjects, such asregional lithology、geochemistry、structural geology、volcanic sedimentology geology、sotope geochronology and synthesis analysis study of geophysics data, are adopted as instrumentality in the paper, this study lays emphasis on the formation, evolution and dynamics of early Neoproterozoic-Cambrian and Carboniferous-Permian volcanic rock in the Tianshan and its adjacent regions to find out Carboniferous-Permian volcanic rock property, eruptive sequence, time and space distribution characteristics, to resume and reconstruct evolution process of Carboniferous-Permian volcanic rock, and to explore connection of magmatism process and lithosphere stretching action of neopaleozoic ocean-land transformation in the Tianshan region.

本文选择分布于天山及其两侧的诸多微陆块上新元古代—早寒武世火山岩和天山地区广泛发育的石炭纪—早二叠世火山岩为研究对象，以恢复重建天山造山带古生代洋陆格局和洋陆转换过程为主线，在详细的野外工作基础上，综合运用区域岩石学、地球化学、构造地质学、火山沉积学、同位素地质年代学、区域地球物理资料综合分析研究等多学科手段，重点研究天山及其邻区新元代—早寒武世和石炭—二迭纪火山岩系的形成演化及其动力学，查明天山石炭纪火山岩系的性质、喷发序列、时空分布特点，恢复重建其形成演化过程，探索天山地区晚古生代洋陆转换过程中火山岩浆作用与岩石圈拉伸作用的关系。

Volcanic rocks of Xishanbulake Formation and Shuiquan Formation are of alkali basalt series, those of Zhamoketi Formation are of alkali basalt series and tholeiite series, and those of Beiyixi Formation are obviously characterized by bimodal assemblage and mostly belong to alkali volcanic rocks.

其中，西山布拉克组和水泉组火山岩均碱性玄武岩系列；扎摩克提组火山岩分属碱性火山武岩系列和拉斑玄武岩系列；贝义西组火山岩具有明显的双峰式组合特徵，大部分属碱性火山岩。

After that the territor ial extensional stress field caused by the plates movement and the mantle upheave etc. makes the Yishu fault system keep on cutting downward tend to form rift valley. The tectonism causes the fairly large-scale invasion of the small neutral -partial alkaline rock-bodies and the gold mineralization in the Linyi area.

燕山中期板块俯冲运动和地幔上涌等因素引起的区域性拉张作用使沂沭断裂继续向下深切张裂，向裂谷性质演化，造成沂南、临沂等地区较大规模中性偏碱性次火山岩型小岩体的侵入和火山喷发，在火山机构内或围绕次火山岩小岩体形成与中性偏碱性次火山岩有关的次火山岩型金矿化。

Our project is based on Cenozoic volcanic rocks and deep seated xenoliths in it to reconstruct the source composition and ctructure. We did field investigation, collection of samples, determination of age and composition characteristics of selected samples. The new achievements are following. 1 recognized a potassic metasomatic source of the Cenozoic volcanic rocks through an integrated research of volcanic rocks and their sources. 2 analysis of TM images suggests the Tuoyun basin is a basin with a volcano group instead of a simple volcano-tectonic basin. We found several volcanic craters and cone, and detected three such craters. 3 systematic reseach of volcanic sections and collection of samples both of volcanic rocks and xenoliths, the later includes peridotite, granulite, gneiss and variety of megacrysts. This is propitious to our further research at this rigion. We would like to point that we collected some peridotite large than 20cm in diameter. It could used to variety of analysis and end the history without mantle chemistry records in the region. 4 we got a U-Pb SHRIMP age of 3.87 Ma for the Kangxiwa basalt.It is the youngest record of U-Pb SHRIMP age in China and provide a chronology restriction for last uplifting of Tibet plateau. 5 the investigation of alkali syenite-synogranite in Taxkogan suggests that the origin of Parmir syntex is related to the Cenozoic magmatism.

本项目立足于从火山岩属性和深源捕掳体反演源区成分与结构两个途径，利用火山岩综合研究成果对地幔源区进行了初步反演，提出源区经受过强烈钾质交代的观点；对重点工作区TM图像进行了初步解译，新发现若干了火山口，并对其中三个火山口作了实地查验，为进一步全面深入开展该区的火山地质学及相关科学问题打下了良好基础，认为托云盆地是一个火山群，而不是一个单一的火山构造盆地；系统测制了火山岩剖面，新采集了一批重要的火山岩和深源岩石捕虏体样品，为下一步工作打下基础，特别是采集到了直径打20cm的幔源橄榄岩包体，可用于各种测试，将可以结束西部造山带没有地幔岩化学分析结果的历史；对康西瓦玄武岩进行了测年分析，取得了我国目前最年轻的锆石U-Pb SHRIMP年龄，对青藏高原挽近地质时期的隆升提供了年代学约束；对帕米尔东缘塔什库尔干碱性岩体的动力学意义进行了探讨，提出青藏高原西部构造结的形成与岩浆活动有关的观点。

This study shows that there are 4 kinds of volcanic facies in deep volcanics in north Songliao Basin: eruptive facies, overflow facies, volcanic vent facies and volcanic sedimentary facies. There are 4 volcanic eruption cycles: Huoshiling period, Shahezi period, Yingchengzi period and Quantou period. There are 4 structural evolution stages: north-south accumulation, west-east subduction, uplift mantle and thin crust, alternative open and close. There are 4 kinds of pool-forming patterns:(1) pattern with the migration along the unconformity and fault to the near crater;(2) pattern with the migration along unconformity and fault to the rift margin;(3) pattern with the migration along unconformity, fault and fracture to the source rock;(4) pattern with the migration of the deep gas along the deep and large fault to the volcanic trap.

研究认为，松辽盆地北部深层火山岩主要存在四种火山岩相：即爆发相、溢流相、火山通道相、火山沉积相，划分为四个火山喷发旋回：即火石岭期、沙河子期、营城子期、泉头期，经历了四个构造演化过程：即南北夹攻、东西俯冲、幔隆壳薄、开合交替，具有四种成藏模式：即沿不整合面和断层运移至近火山口处火山岩圈闭聚集成藏模式、沿不整合面和断层砂岩疏导层运移至断陷边部火山岩圈闭聚集成藏模式、沿不整合面及断层、裂缝运移至源岩区内凹中隆火山岩圈闭聚集成藏模式、深部无机成因天然气沿深大断裂运移至火山岩圈闭聚集成藏模式。

In addition, the features of elemental geochemistry of all samples suggest that (1) the EarlyTriassic andesitic rocks, characterized by characteristic natures of island arc volcanics, likely erupted in the subduction setting; that (2) the generation of LateTriassic rhyolites with an affinity of Alike granite and synchronously main body granites in the Lincang batholith displaying similar geochemical features, is closely related with the postcollision or latecollision setting; that (3) although the LateTriassic basic rocks partly show island arc volcanics such as highAl contents and NbTa depletion, some of them possessing highMg contents and mostly having traceelement ratios similar to intraplate basalt, which indicates that they erupted in the postcollision rift environment.

元素地球化学特征表明，早三叠世火山岩具有典型的岛弧火山岩的特征，暗示其很可能形成于俯冲的构造环境；中三叠世晚期的流纹岩与临沧花岗岩基主体具有非常相似的地球化学特征，结合其流纹岩具有A型花岗岩属性，表明该区中三叠世火成岩形成于碰撞后的构造背景；而晚三叠世基性火山岩虽然在地球化学特征上显示出与岛弧火山岩相似的高铝和NbTa的亏损，但其中部分火山岩具有高镁和板内玄武岩的微量元素比值特征，说明这些火山岩可能形成于碰撞后裂谷环境。

Kalamaili suture zone is an important plate boundary in north Xinjiang, and there are plenty of Neopaleozoic volcanic rocks around itThese volcanic rocks are enriched in LILEs and relatively depleted in HFSEs, and they are also characterized by high Nb, Zr, TiO2 contents and Zr/Y, Nb/Y ratios, and depleted SrNd isotopesThe characteristics of these volcanic rocks suggest that they were produced in postcollisional periodThe postcollisional volcanic rocks around Kalamaili suture zone become younger from west to east, which indicates that this suture zone entered postcollisional period gradually from west to east, and reflects that the Kalamaili Ocean had been closed gradually from west to eastAs to the Kalamaili suture zone in postcollisional period, the lithosphere extended and thinned, and the asthenosphere materials upwelled and melted partially, and intensive mantle convection occurred, leading to a plenty of mantlederived magmas underplating the suture zoneThe lithospheric mantle metasomatized by fluid in subduction period melted partially under decompression and high temperature, the resulting melts contaminated the underplating asthenospheric materials, and the erupted lavas became the Neopaleozoic postcollisional volcanic rocks

卡拉麦里缝合带是北疆的一条重要界线，沿该带广泛发育晚古生代火山岩。这些火山岩具有LILE相对富集、HFSE相对亏损的特征，且具有较高的Nb、Zr、TiO2含量和Zr/Y、Nb/Y比值，SrNd同位素主要表现出亏损的特征。综合分析表明，这些火山岩形成于后碰撞期。对卡拉麦里缝合带而言，从西向东后碰撞火山岩的时代逐渐变新，表明该缝合带从西向东逐渐演化进入后碰撞期，这从侧面反映了卡拉麦里洋盆是从西向东逐渐关闭的。对卡拉麦里缝合带而言，在后碰撞期，岩石圈伸展减薄，软流圈地幔物质上涌并发生部分熔融，加上地幔对流作用强烈，使得缝合带下产生了大规模的幔源岩浆底垫；先前在洋壳消减期被流体交代提取过的岩石圈地幔也在低压高温下发生部分熔融，形成的熔体混染了底垫的软流圈物质并喷发，形成了晚古生代的后碰撞期火山岩。

Tectonic condition is the key factor for igneous rock reservoir, which produce crack and improve reservoir character, abundant generating rock is the foundation for igneous rock reservoir, lithology condition is the important supplement for igneous rock reservoir, it is easy for trachyte to produce crack.

综合分析构造条件是火山岩成藏的关键，其产生的裂缝改善了火山岩储层的储集性能；充足的油源条件是火山岩成藏的基础；岩性条件是火山岩成藏的重要补充，即粗面岩容易在构造作用下形成构造裂缝，最终形成火山岩油气藏。

Since development of volcanic layers and volcanic mounds in basement in Tazhong area, using seismic exploration is usually difficult to acquire better seismic data in the interior of vocatine and below(mainly caused by shield of volcanic layer), but using MT exploration may not produce such problem, because the electromagnetic wave does not suffered from the shield of higher resistance layer; especially the volcanite has the feature of higher magnetic susceptibility and impedance, which provides excellent c...

由于塔中地区的火山岩层及基底火山岩丘发育，采用地震勘探方法通常难以在火山岩内部及其以下获得比较好的地震资料(主要是火山岩层的屏蔽作用)，而利用MT勘探则无此问题，因为电磁波不受高阻地层屏蔽，尤其是火山岩具有高磁化率和高电阻率的特征，从而为在该区应用大地电磁和磁力方法识别火山岩薄层及基底火山岩丘提供了得天独厚的条件。

The split between the two groups can hardly be papered over.

这两个团体间的分歧难以掩饰。

This approach not only encourages a greater number of responses, but minimizes the likelihood of stale groupthink.

这种做法不仅鼓励了更多的反应，而且减少跟风的可能性。