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1.
库米什地区火山岩属该区蛇绿岩套的组成部分,形成于晚泥盆世,以中性和酸性岩石为主,火山碎屑岩较发育,具有钙碱性火山岩套的特征。岩套内的沉积夹层具有远海沉积的性质。火山岩岩石化学特征属钙碱性系列;微量元素地球化学证明岩浆起源于消减板块之上的地幔楔形区;稀有元素地球化学特征与安山岩的特征相符。综合分析这些证据发现,该区火山岩形成于弧后盆地环境。 相似文献
2.
Zuxing Chen Zhigang Zeng Xiaoyuan Wang Yuxiang Zhang Xuebo Yin Shuai Chen Yao Ma Xiaohui Li Hanyan Qi 《中国海洋大学学报(英文版)》2017,16(6):1097-1108
To reveal the petrogenesis of rhyolite from the southwestern Okinawa Trough, the mineral chemistry of plagioclase, orthopyroxene, amphibole, quartz and Fe-Ti oxide phenocrysts were analyzed using an electron microprobe, and in suit Sr and Ba contents of plagioclase analysed by LA-ICPMS were chosen for fingerprinting plagioclases of different provenances. Results indicate an overall homogeneous composition for each of the mineral phases except for plagioclase phenocrysts which have a wide range of composition(An=39~88). Plagioclase crystals characterized by An contents of 70 are not in equilibrium with their whole-rock compositions, and coarse-sieved plagioclase phenocryst interiors record high An contents(70) and Sr/Ba ratios(7), which are similar to the those of plagioclase crystals in basalt. Therefore, these crystals must have been introduced to the rhyolitic magma from a more mafic source. Equilibrium temperatures estimated using orthopyroxene-liquid, iron–titanium oxide, titanium-in-quartz and amphibole geothermometers show consistent values ranging from 792 to 869℃. The equilibrium pressure calculated using amphibole compositions is close to 121 MPa which corresponds to an approximate depth of 4 km. The fO_2 conditions estimated from Fe-Ti oxides and amphiboles plot slightly above the NNO buffer, which indicates that the rock formed under more oxidized conditions. Our results suggests that petrogenesis of the rhyolite due to basaltic magma ascend with the high An and Sr/Ba plaigoclases from deep magma chamber into the shallow chamber where the fractional crystallization and crustal assimilation happened. It also indicates that a two-layer magma chamber structure may occur under the southwestern Okinawa Trough. 相似文献
3.
沂沭裂谷及邻区下白垩世火山熔岩以碱性系列的玄武粗安岩、粗安岩、粗面岩为主。而亚碱性系列以钙碱性为多。碱性系列以钾质亚系列为主，其中鲁东、鲁西基本上是钾质亚系列，而沂沭裂谷内有一定数量的钠质亚系列。稀土元素标准化曲线均呈向右陡倾斜，其斜率相似，为典型的富轻稀土，而亏损重稀土的型式。多数δＥｕ在０．７８－１．２８之间。 相似文献
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5.
新疆卡拉麦里姜巴斯套组火山岩地球化学特征与构造意义 总被引：7，自引：0，他引：7
通过对新疆卡拉麦里姜巴斯套组火山岩野外地质特征、岩石学和高精度同位素年代学的研究,发现姜巴斯套组火山岩具典型双峰式组合,岩石类型包括玄武岩-酸性火山碎屑岩-玄武粗面安山岩;得到玄武粗面安山岩LA-ICP-MS锆石U-Pb年龄为(319.8±2)Ma(加权均方偏差值为3),表明姜巴斯套组火山岩形成于早石炭世谢尔普霍夫阶。对火山岩地球化学特征的研究表明,姜巴斯套组火山岩钙碱性系列、高钾钙碱性系列和钾玄岩系列岩石兼而有之,岩石的稀土元素配分曲线均为轻稀土元素富集型,无明显Eu异常,玄武岩和玄武粗面安山岩具有K正异常和Sr负异常,酸性火山碎屑岩表现出Nb、Ta和Ti显著亏损。总体来说,姜巴斯套组火山岩富集大离子亲石元素,相对亏损高场强元素。玄武岩和玄武粗面安山岩表现出大陆裂谷(大陆板内拉张区域)岩石特征;酸性火山碎屑岩表现出岛弧或者活动大陆边缘岩石属性。总之,姜巴斯套组火山岩形成于卡拉麦里洋盆闭合碰撞造山后的拉张伸展环境,卡拉麦里地区在早石炭世末期就进入了碰撞后的陆内伸展拉伸阶段。 相似文献
6.
Mohammed Hazaea HU Ke Mohammed Mattash CHEN Bing M.O.Al-Jabali Aref Mohammed Abdussalam 《世界地质(英文版)》2004,7(2)
The chemical composition of several thermal springs around Changbaishan area has been investigated.Cenozoic basaltic rocks are widely distributed in Northeast China and geothermal characteristics have been described.About one hundred hot springs exist around Changbaishan Volcano at the border between China and D.P.R.Korea with high temperature about 82℃. The pH values of the spring water range from 6.9 to 7.1 and the total flow rate is about 4.8 L /sec. The chemical composition of the thermal springs is sodium carbonate; the high-mineral contents of thermal water are believed to have medicinal properties. Bathhouses are already built along the hot springs to take the advantage of the supposed healing properties. The high quality of those hot springs is believed to be utilitized for mineral water. The chemical equilibrium temperatures were estimated at about 160℃ based on the Na-K-Ca geochemical thermometer. 相似文献
7.
安徽南陵-宣城地区是一个中-新生代火山-沉积盆地,位于长江中下游构造-岩浆-成矿带东北段的东南翼。对该区发育的岩浆岩开展了较为系统的LA-ICP-MS锆石U-Pb定年及岩石主量、微量和稀土元素分析,并与长江中下游构造-岩浆-成矿带其他地区岩浆岩进行对比,旨在确定岩浆岩的成岩时代、探讨岩浆岩成因及其与成矿的关系。南陵-宣城地区岩浆岩一部分侵入于盆地基底中,另一部分喷发形成盆地盖层,还有一部分产于盆地之上的推覆构造(体)中。侵入岩的岩性主要为花岗岩、花岗闪长岩、石英闪长岩、辉石闪长岩等,火山岩主要为英安质火山碎屑岩和熔岩。获得的侵入岩锆石U-Pb年龄主要为138~135 Ma,火山岩年龄均小于134 Ma,表明岩浆作用发生于晚中生代(燕山晚期)早白垩世。岩浆岩主量元素显示高Si、K的特征,为亚碱性高钾钙碱性系列岩石;微量元素组成显示岩浆岩富集Rb、Th、U、K等大离子亲石元素,亏损Nb、Ta、Ti等高场强元素,火山岩比侵入岩较为亏损Sr和P;球粒陨石标准化稀土元素配分模式均表现为富集轻稀土元素的右倾模式和较弱的Eu负异常。元素地球化学特征指示区内岩浆岩具有壳幔混源且以幔源为主的特征。南陵-宣城地区既发育与长江中下游构造-岩浆-成矿带隆起区(如铜陵地区)同位素地质年龄和地球化学特征基本一致的侵入岩,又发育与凹陷区(如庐枞、宁芜等盆地)同位素地质年龄和地球化学特征基本一致的火山-次火山岩,显示该区晚中生代岩浆作用具有长江中下游构造-岩浆-成矿带隆起区和凹陷区的双重特征。岩浆作用的双重特征暗示与其有关的成矿作用也可能具有双重性,即既可能发育与隆起区侵入岩浆作用有关的斑岩型、矽卡岩型和脉型铜金等多金属矿床,也可能发育与凹陷区火山-次火山岩有关的玢岩型铁(硫)矿床。 相似文献
8.
The petrogenesis and geodynamic setting of the Late Jurassic Baita porphyry quartz monzodiorite in Xingcheng--Liaoxi area provide information for understanding the Mesozoic tectonic evolution of the northeastern North China Craton. In this paper, geochronological, whole-rock geochemical, and in-situ zircon Hf isotopic analyses of Baita porphyry quartz monzodiorite were investigated to constrain the crystallization age and petrogenesis. Zircons exhibit typical oscillatory zoning in cathodoluminescence images and show relatively high Th/U ratios(0.78--1.62), and U-Pb analyses indicate that these rocks were crystallized during the Late Jurassic(159±1 Ma). Geochemically, they are characterized by high contents of SiO_2(65.21 wt%--65.31 wt%), Al_2O_3(16.29 wt%--16.31 wt%), Sr(521×10~(-6)-539×10~(-6)), and Sr/Y ratio(45.1--47.8) but low Y(10.9×10~(-6)-12.0×10~(-6)), with obvious adakitic geochemical affinities. These above-mentioned findings, combined with their negative ε_(Hf)(t) values(-21.7 to-20.2), corresponding two-stage model age(T_(DM2)) of 2 579--2 484 Ma, as well as low MgO(1.38 wt%--1.39 wt%), Cr(18.5×10~(-6)-19.5×10~(-6)) and Ni(9.45×10~(-6)-9.46×10~(-6)) values, indicate that Baita porphyry quartz monzodiorite may be generated by partial melting of the Neoarchean-Paleoproterozoic thickened basaltic lower crust. Based on the results from this study and pre-vious regional studies, it is concluded that Baita porphyry quartz monzodiorite was spatially related to the westward subduction of the Paleo-Pacific plate. 相似文献
9.
四川西南部前震旦纪康定杂岩,主要由英云闪长质深成岩和一些具残留顶盖特征的变质地层组成。深成岩体呈南北向线性展布,实地接触关系证明,它们是晚于围岩的侵入体;而且岩相学和地球化学特征表明,深成岩是玄武质源的岩浆分离结晶作用产物.结合区内岩石构造组合,可以推断英云闪长质深成岩是在位于陆缘型岩浆弧近大洋的构造环境下形成.鉴于康定杂岩的岩石组合及地球化学特征与太古代地体存在明显差别,其时代应属于元古代. 相似文献
10.
Qinghai Wang Wenliang Xu Dongyan Wang Jingqian LinCollege of Earth Sciences Jilin University Changchun China 《东北亚地学研究》2003,(2)
1IntroductionAdakite has specially sense in the resuming structure background of rock formed,because of its distinctive geochemistry feature and implying partic-ular petrogenesis and ore genesis mechanism (De-fant and Drummond,1990),as a result,it arouses numerous researchers widely concern. After adakite conception was drawn by Chinese (Wang etal.,2000), it was widely concerned by domestic re-searchers (Wang etal.,2000,2001a,2001b;Xu etal.,2000;Pan etal.,2001;Qian,2001;Xu etal.,2001;X… 相似文献
11.
Sediment cores (∼40–100 cm) were collected at 12 locations in the western Bohai Bay, the Haihe River estuary, the Yongding
River estuary and the Tianjin Harbor, China, during 24–26 July 2007, and analyzed for 7Be and 210Pb activities. Due to localized hydrodynamic patterns and frequent disturbance from dredging activities, steady-state sedimentation
features were not observed in this study. As demonstrated in the 7Be and 210Pb profiles, the temporal and spatial variations of these radionuclides support a non-steady state depositional environment
in the study area. By comparing 7Be and 210Pb inventories in the sediments with those of the atmospheric source, we found that: 1) sediments dredged from the Tianjin
Harbor or eroded from nearby estuarine and coastal areas are retained in the western Bohai Bay for relatively short intervals
(several months), as reflected in the relatively high 7Be inventories in the western Bohai Bay; 2) over the long-term (years to decades), 210Pb inventories in the sediments imply that there is a net on-shore transport of sediments, and the sediments are mass-balanced
in the entire study area. Overall, our results suggest that the sediments are retained in the estuaries and the western Bohai
Bay despite local variability in sediment dynamics and disturbance due to human activities. 相似文献
12.
The research of the petrology and the geochemistry of the Mosozoic intrusive rocks in Xu-Huai area indicated that they are mainly composition of dioritic porphyry and monzodioritic porphyry, and the features of the petrology and geochemistry of the Mosozoic intrusive rocks are extremely similar to those with the typical adakites. Combined with the petrography and the testimated results of the deep-seated xenoliths in the intrusive rocks, it indicates that the petrogenesis of the Mosozoic intrusive rocks could be resulted from the partial melting of amphibole-bearing garnet pyroxenite and garnet amphibolite in lower continental crust in this area. 相似文献
13.
中国大陆科学钻探先导孔零偏VSP资料解释 总被引：3，自引：3，他引：0
用六级三分量检波器在中国大陆科学钻探先导孔中实施了零偏VSP测量.数据处理结果表明,中国大陆科学钻探孔区超高压变质岩石的地震波速度主要介于4500～7000m/s之间,显著高于一般的沉积岩地区,而且随深度变化不明显.声波测井速度系统地稍低于VSP层速度,可能是由于井壁处岩石的完整性受到破坏而造成的.地震波速度与岩石密度和岩性存在明确的对应关系,榴辉岩的密度和地震波速度均显著高于片麻岩类岩石;由榴辉岩退变生成的斜长角闪岩类岩石,其密度和地震波速度均呈现出较大的变化,主要与其退变质程度有关;超基性岩中的裂隙系统导致其密度和地震波速度大幅度下降.由于榴辉岩与其他岩石类型之间存在较大的波阻抗差异,因此用零偏VSP资料标定该区地震波的地质层位是有效的.关于地震波反射的原因,通过综合研究地震波(包括反射纵波、上行转换横波、井筒波)的特征、岩石速度和密度分布以及井径变化,认为主要是岩性分界面、韧性剪切带和断裂(带),但还有一些因素尚待进一步研究. 相似文献
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以往都将研究区内商丹断裂南侧的岩石定为角岩化碎屑岩或火山岩,划归泥盆系青石垭组或加里东蛇绿岩套。笔者认为这些岩石是一套糜棱岩,不是一个独立的地层单位。对该区的长英质、富铝质、斜长角闪质和碳酸盐质四类糜棱岩,分别做了岩相学特征描述。通过化学成分、矿物成分、碎斑矿物特征和变余构造恢复了各种糜棱岩的原岩。并讨论了这些原岩的时代归属,认为这些原岩分别来自秦岭群、丹凤群和中泥盆统,说明有不同时代、不同成因的地质体卷入了这条韧性剪切带。 相似文献
16.
本文以南海周边的岘港湾和深圳湾为研究对象,选取了1987年和2015年的遥感影像,基于土地利用转移矩阵、土地利用动态度模型和土地利用程度模型,对2个海湾近30年来的土地利用变化情况进行了对比研究,对所属海岸带的绿地、围填海及城市扩张等变化程度进行了整体分析,透过海湾不同的土地利用特征探究其发展情况。研究结果表明：（1）深圳湾原本的耕地全部被开发为城镇用地,约51%的养殖用地转变为城镇用地,而岘港湾约有86%耕地转化为城镇用地,养殖用地面积则增加了1.43 km2;（2）深圳湾填海造陆面积达32 km2,岘港湾填海造陆面积约5 km2,远小于深圳湾的造陆强度;（3）岘港湾城镇土地增加速度略高于深圳湾,其2015年土地利用综合指数为283.28,而深圳湾在1987年就达到274.12,且2015年该值高达320.52,岘港湾的土地利用综合指数远低于同期深圳湾的水平,岘港湾的土地利用呈现出明显的工业化中期的土地利用特征,而深圳湾则已进入工业化后期;（4）岘港湾裸地面积增加了3.5倍,而深圳湾没有增加,深圳湾的红树林面积增加了2.1倍,而岘港湾的红树林在1987年前已消失,深圳湾的开发方式更注重对自然土地类型及功能性绿地的保护。 相似文献
17.
Wang Pengpeng Zhang Fang Sun Song Wang Weicheng Wan Aiyong Li Chaolun 《中国海洋湖沼学报》2020,38(4):1256-1269
The population explosion of jellyfish Aurelia coerulea occurred in Jiaozhou Bay,China in 2009.The potential predation impact of A.coerulea on zooplankton was investigated.Population clearance potential and residence time(t_(1/2)) for copepods were calculated from laboratory clearance rates and measurements of jellyfish size and abundance from May to August 2009 in Jiaozhou Bay.Clearance rates varied widely with prey organisms,but they were not significantly different among various prey concentrations.Medusae captured rotifers,fish larvae and hydromedusae more efficiently than fish eggs,copepods and chaetognaths.Ephyrae captured rotifers and hydromedusae more efficiently than fish larvae and copepods.Clearance rate linearly increased with the cro s s sectional area of A.coerulea(size from 0.3 to7.1 cm).Water temperature also had a marked effect on clearance rate and this was related to the increased beat freque ncy as water temperature increased.In early May 2009,A.coerulea potentially cleared the volume of water in the Bay less than 0.001 times a day,but this value was estimated to be more than 0.3 times a day in July.The t_(1/2) for copepods was less than 6 d in June and July.Abundances of copepods,hydromedusae and chaetognaths were extremely low in 2009 compared to 2008 and 2010(jellyfish non-bloom years).Large predation pressure by the A.coerulea population occurred to control zooplankton communities in Jiaozhou Bay.A.coerulea,when present at a high population level,can be a keystone species in Jiaozhou Bay and control the trophic structure here. 相似文献
18.
《山地科学学报》2015,(5)
The goal of this study is to determine the geometrical and geotechnical characteristics of landslides under various geological conditions using detailed field surveys, laboratory soil tests and precipitation records. Three study areas are selected to consider different rocks, including gneiss in Jangheung, granite in Sangju and sedimentary rocks in Pohang, South Korea. Many landslides have occurred in these three areas during the rainy season.Precipitation records indicate that landslides occurring in the gneiss area of Jangheung and granite area of Sangju may be influenced by the hourly rainfall intensity rather than cumulative rainfall.However, landslides occurring in the sedimentary rock area of Pohang may be influenced by hourly rainfall intensity and cumulative rainfall. To investigate the factors that influence these types of landslides, a detailed landslide survey was performed and a series of laboratory soil tests were conducted.According to the detailed field survey, most landslides occurred on the flanks of mountain slopes, and the slope inclination where they occurred mostly ranged from 26 to 30 degrees, regardless of the geological conditions. The landslide in the gneiss area of Jangheung is larger than the landslides in the granite area of Sangju and sedimentary rock area of Pohang.Particularly, the landslide in the sedimentary rock area is shorter and shallower than the landslides in the gneiss and granite areas. Thus, the shape and size of the landslide are clearly related to the geological conditions. According to the integrated soil property and landslide occurrence analyses results, the average dry unit weight of the soils from the landslide sites is smaller than that of the soils obtained from the nonlandslide site. The average coefficient of permeability of soils obtained from the landslide sites is greater than that of soils obtained from the non-landslide sites with the same geology. These results indicate that the soils from the landslide sites are more poorly graded or looser than the soils from the non-landslide sites. 相似文献
19.
通过对青海滩间山金矿花岗质岩石的岩石化学、稀土元素和铅同位素研究,证明了和金矿有关的花岗质岩浆源于加里东期基性超基性岩的部分熔融或同源玄武岩分离结晶。岩浆中富金属硫化物的热液以及岩浆自身的热能,为地层和岩浆中金元素的活化和运移提供了能量和载体,对金起着捕获和富集的作用,有利于金矿床的形成。 相似文献
20.
The alkaline oceanic island basalts(OIBs) with under-saturated SiO_2 and high contents of CaO and alkaline are usually attributed to mantle sources different from typical tholeiitic OIBs.Based on the results of high pressure and temperature experiment study,the genesis of silica under-saturated alkaline basaltic melts could be explained by the role of CO_2, thus,the genetic relationship of alkaline basalts with CO_2 has become a topic of relevance because it is closely related to the deep carbon cycle.The Magellan Seamount chain in the West Pacific Seamount Province has wide distribution of alkali basalts.For the first time,we collected alkaline basalt samples from the Kocebu Seamount of the Magellan Seamount chain and found that magmatic apatites widely occur in the less evolved volcanic rock samples,and the high contents of phosphorus should be a feature of the alkaline OIB s of the Magellan Seamounts.Compared with typical OIBs,these alkaline volcanic rocks have higher CaO and P_2 O_5, lower SiO_2 content,negative anomaly of high field strength elements(HFSEs),more distinctly negative anomaly of potassium(K) and the ubiquity of titanaugite,indicating a CO_2-rich mantle source.Based on the relatively high K2 O and TiO_2 contents and La/Yb ratio and low MgO content of these alkaline rocks,we suggest that the volcanic rocks of the Magellan Seamounts are originated from carbonated eclogites derived possibly from ancient subducted altered oceanic crust. 相似文献