SHRIMP U-Pb zircon age of tuff from the Kunyang Group in central Yunnan： Evidence for Grenvillian orogeny in South China

Whether or not Grenvillian orogeny occurred in South China still remains highly controversial because high-quality,discriminating data are lacking,and therefore,the key to resolve this matter is to find datable volcanic and/or sedimentary rocks related to Grenvillian orogeny. Such rocks are apparently present in the Fuliangpeng Member from the lower-middle part of Kunyang Group in central Yunnan; here the unit is more than 100 m thick and consists of andesitic ignimbrite,tuffite,terrigeous clastic rocks and carbonates. These volcanic rocks,developed south of the Sibao fold-thrust belts,represent the earliest calc-alkaline volcanic activity in late Precambrian time from central Yunnan and are coeval with both a change in sedimentary facies from detritus to carbonates and the beginning of seismite development elsewhere. Two samples for SHRIMP analysis were collected from this volcanic unit. Sample G3-29-2,from the bottom of Fuliangpeng Member,is an ignimbrite,and about 100 zircon crys-tals recovered from it have euhedral shapes and display relatively simple sector zonation under cathodoluminescent (CL) imaging,suggesting a magmatogenic origin. Twenty-five of the zircons were analyzed and a weighed-mean U-Pb age of 1032±9 Ma was obtained. Sample G3-29-3 from uppermost part of Fuliangpeng Member is a tuffite,and many rounded,evidently detrital zircons were recovered. Nine of these zircons were analyzed,and the oldest single-grain U-Pb zircon age is 1938±26 Ma,im-plying that Paleoproterozoic basement developed in Cathaysia. The dating result,combined with the geotectonic research on the Fuliangpeng Member,leads us to conclude that late Mesoproterozoic orogenic volcanic activity occurred in the western part of South China,and that the related collision of Yangtze and Cathaysian cratons was an integral part of the assembly of Rodinia.     

滩间山群火山岩特征及其成岩构造背景

滩间山群火山岩分为下部火山碎屑岩组(O1-2h)和上部熔岩次火山岩组(O3y)。从岩石组合、岩石化学、地球化学等方面进行了研究,指出下部火山岩总体体现大陆裂谷环境特征,上部火山岩总体显现类岛弧环境特征,由下至上,由双峰式火山岩向类岛弧钙碱性火山岩演变,揭示其成岩构造背景是经历了大陆裂谷、逐渐稳定、俯冲到类岛弧火山岩形成的几个阶段。     

Effects of nitrogen sources and glucose on the consumption of ethylene and methane by temperate volcanic forest surface soils

There is limited knowledge with regard to the consumption of ethylene (C2H4) and methane (CH4) in volcanic forest soils containing low microbial carbon-to-organic carbon ratio, and to the responses of both consumptions to nitrogen and carbon additions. Temperate volcanic forest surface soils under three forest stands (e.g. Pinus sylvestris L., Cryptomeria japonica and Quercus serrata) were used to compare CH4 and C2H4 consumption by forest soils, and to study the effects of nitrogen sources and glucose on both consumptions. There was a good parallel between CH4 and C2H4 consumption by for- est soils, but mineralization reduced CH4 consumption rather than C2H4 consumption in forest soils, particularly in a Pinus forest soil. The stimulatory effect of glucose addition on both CH4 and C2H4 consumption by forest soils was increased by increasing the pre-incubation period after glucose addi- tion, and a largest stimulation occurred in the Pinus forest soil. The addition of KNO3-N at the rate of 100 μg·g1 significantly reduced the consumptions of both C2H4 and CH4 by forest soils (P≤0.05). In the presence of urea plus dicyandiamide, the consumption rates of C2H4 and CH4 by forest soils were higher than those in the KNO3-N and urea-N treated soils at the same N rate (P≤0.05), but were similar to those of the control. Hence, under experimental conditions, there was a strong inhibitory effect of NO3 rather than NH4 addition on the CH4 and C2H4 consumption in these forest soils. When amount of the added NO3-N increased up to more than 2―3 times the soil initial NO3-N concentrations, both C2H4 and CH4 consumption rates were reduced to 10%―20% of the rates in soils without nitrate addition. By comparing the three forest stands, it was shown that there was a smallest effective concentration of the added nitrate that could inhibit C2H4 and CH4 consumption in the Pinus forest soil, which indicated that C2H4 and CH4 consumption of the soil was more sensitive to NO3-N addition.     

Chronological record of the Early Mesozoic underplating in the northern margin of North China─U-Pb chronometry of zircons in the Late Mesozoic andesite from Western Liaoning

Cathodoluminescence spectroscopic analysis of zircons in the uppermost sanukites of the early Cretaceous Yixian Formation in Western Liaoning reveals zoning structures of the zircons in the volcanic rocks. LA-ICP-MS chronometry shows that the central part of the zircons is remnant zircon with a U-Pb dating of 254 Ma, which is consistent with the age of the Early Mesozoic underplating granulites, and that the periphery is zircon crystallizing out of the host magma with a U-Pb dating of 116 Ma, which is highly consistent with the Ar-Ar dating of the host volcanic rocks. Compositions of the clinopyroxenes xenocrystals in the sanukites are similar to those of the clinopyroxenes in the underplating granulites, indicating that the granulites accreted to the lower crust in the Early Mesozoic have been reformed and disrupted by the upwelling diapers of the asthenosphere and taken part in formation of the sanukites in the Late Mesozoic.     

Chronological record of the Early Mesozoic underplating in the northern margin of North China—U-Pb chronometry of zircons in the Late Mesozoic andesite from Western Liaoning

Cathodoluminescence spectroscopic analysis of zircons in the uppermost sanukites of the early Cretaceous Yixian Forma- tion in Western Liaoning reveals zoning structures of the zircons in the volcanic rocks. LA-ICP-MS chronometry shows that the central part of the zircons is remnant zircon with a U-Pb dating of 254 Ma,which is consistent with the age of the Early Mesozoic underplating granulites,and that the periphery is zircon crystallizing out of the host magma with a U-Pb dating of 116 Ma,which is highly consistent with the Ar-Ar dating of the host volcanic rocks.Compositions of the clinopyroxenes xenocrystals in the sanukites are similar to those of the clinopyroxenes in the underplating granulites,indicating that the granulites accreted to the lower crust in the Early Mesozoic have been reformed and disrupted by the upwelling diapers of the asthenosphere and taken part in formation of the sanukites in the Late Mesozoic.     

Potash-rich volcanic rocks and lamprophyres in western Shandong Province: 40Ar-39Ar dating and source tracing

Highly precise ⁴⁰Ar-³⁹Ar dating results demonstrate that the ages of potash-rich volcanic rocks in western Shandong Province are 114.7–124.3 Ma, and that of the lamprophyres is 119.6 Ma. The potash-rich volcanic rocks have relatively high (⁸⁷Sr÷⁸⁶Sr)_i ratios (0.708715–0.711418) and distinctly negative ε_nd values (−11.47–−17.54), and are enriched in radiogenic lead (²⁰⁶Pb÷²⁰⁴Pb=17.341−17.622, ²⁰⁷Pb÷²⁰⁴Pb=15.525−15.538, ²⁰⁸Pb÷²⁰⁴Pb = 37.563−37.684). Similarly, the lamprophyres also have quite low ε_nd values (−11.57–−19.64). Based on the fact that the Sr, Nd and Pb isotopic compositions of potash-rich volcanic rocks are very consistent with that of the clinopyroxene separates, and by integrating comprehensive analyses of their tectonic settings, and extensive comparisons of the Sr, Nd isotopic compositions with that of the related simultaneous rocks, it is concluded that the potash-rich volcanic rocks and lamprophyres in western Shandong Province were most possibly derived from the partial melting of enriched mantle which was caused by source contamination and metasomatism of subducted continental crustal materials.     

平坡矿区煤层夹矸中的IS有序混层矿物

产于甘肃山丹平坡矿区太原组中段顶三槽煤层夹矸中的I/S混层矿物为IS型有序混层。它主要由Na-Ca或Ca-Na型蒙皂石层和似2M_1型伊利石层组成。混层矿物的原始物质主要为火山凝灰质,并且形成于蒙皂石向伊利石的成岩转化过程中。     

火山喷发柱物理机制的理论探讨

浮力射流现象（又称羽流），是自然界很普遍的一种物理现象．世界上中最壮观的羽流现象是由爆炸性火山喷发的各种火山气体、细粒的火山喷发碎屑物所组成的火山喷发柱，也就是我们俗称的火山蘑菇云．火山喷发柱的强弱和类型受火山喷发柱流体物理性质、动力状况力和周围环境条件的制约．本文重点讨论了火山喷发柱的地表部分的物理机制．在分析前人在此方面的实验数据和成果之后，初步得出了我们自己的一些观点和看法．     

惠民凹陷阳信洼陷火成岩及其对油气成藏的影响

通过岩心观察、薄片鉴定、有机地球化学分析等技术手段,对阳信洼陷火成岩岩性特征、储集空间类型、物性特征及其对油气成藏的影响进行了分析,并进一步对阳信洼陷火成岩的发育和时空分布特征进行了研究。结果表明,阳信洼陷火成岩特别发育,火成岩的形成与分布主要受断裂活动的影响,同时火山活动对盆地演化、油气生成、圈闭形成和油气成藏具有一定的控制作用。火成岩及其岩浆作用有利于烃源岩的富集,提高了地温场,改变了地球化学场,促进了有机质生烃作用。阳信洼陷火成岩储集空间发育,具有油气充注率高、油气保存条件好的特点,有利于形成与火成岩有关的复合油气藏。     

流纹岩类火山岩储层物性特征研究

火山岩油气藏储层岩石类型特殊、孔隙结构复杂,在开发过程中其储层物性将会对采出程度产生一定的影响,利用火山岩气田升深2-1井的流纹岩岩心、测井资料,通过对流纹岩岩石物性参数随净上覆岩层压力变化的实验研究,对实验结果进行处理分析,得出了一些有益的结论:该流纹岩岩石孔隙度随净上覆岩层压力呈多项式(三项式)函数变化关系、渗透率与净上覆岩层压力之间的关系满足幂指数关系、储层岩石的压缩系数与净上覆岩层压力之间的关系满足指数关系、岩石密度和孔隙度之间具有很好的线性关系。从而更进一步认识了该流纹岩储层的物性特征,为该特殊岩石气藏的合理开发提供了有利的基础资料。