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1.
大兴安岭温布其地区白音高老组火山岩主要由流纹质岩屑晶屑凝灰岩和流纹岩等一系列酸性火山岩构成。LA-ICP-MS锆石U-Pb测年结果显示,研究区流纹岩形成于(131±1.5)Ma,为早白垩世;岩石地球化学研究表明,样品具有高硅SiO_2(72.43%~78.64%)、富铝Al2O3(11.48%~14.24%)、富钾K_2O(4.09%~5.05%)和低镁MgO(0.14%~0.34%)的特点;轻重稀土分馏较明显[(La/Yb)_N=8.22~13.68],Eu负异常明显(δEu=0.39~0.90);微量元素相对富集大离子亲石元素Rb、Ba、K,亏损高场强元素Nb、P、Ti。~(176)Hf/~(177)Hf比值为0.282 830~0.282 983,εHf(t)为6.02~10.19。研究发现,温布其地区白音高老组火山岩岩浆来源于新元古代亏损地幔增生的年轻基性地壳的部分熔融,形成于伸展的构造环境。 相似文献
2.
针对西藏则学结仁-朗日火山岩的野外地质、岩石学、锆石U-Pb定年以及岩石地球化学等方面的系统研究,结果表明:结仁-朗日火山岩为一套中酸性的火山熔岩及碎屑岩,火山作用以爆发作用为主,岩石类型主要为粗面岩、英安岩及流纹质晶屑岩屑凝灰岩。其LA-ICP-MS锆石U-Pb年龄为50.2Ma±2.2Ma~56.18Ma±0.60Ma,并非前人厘定的嘎扎村组(N2g)火山岩,而属林子宗群年波组(E2n)火山岩。结仁-朗日火山岩具有高K(K2O质量分数为2.68%~4.09%)低Ti(TiO2质量分数为0.69%~0.85%)、高钾钙碱性-钾玄岩系列的主量元素岩石地球化学特征;其稀土配分模式呈轻稀土富集的右倾曲线,LaN/YbN比值为9.13~14.29,普遍出现负铕异常(δEu=0.35~0.84);微量元素方面表现为Nb,P,Ti的亏损;结仁-朗日火山岩具有高放射成因Pb的同位素组成特征。总体上,结仁-朗日火山岩形成于雅鲁藏布洋壳向北俯冲到印度板块与欧亚大陆碰撞的过渡环境,岩浆起源于楔形地幔部分熔融所形成的基性岩浆在上升过程中混染陆壳熔融所形成的酸性岩浆。 相似文献
3.
锡林浩特东部早白垩世白音高老组岩石地球化学特征、LA-MC-ICP-MS锆石U-Pb年龄及地质意义 总被引：6，自引：0，他引：6
锡林浩特东部白音高老组火山岩主要由石泡流纹岩、珍珠岩、碎斑熔岩、流纹质熔结凝灰岩等组成。LA-MC-ICP-MS锆石U-Pb定年显示,火山岩形成于134 Ma~139 Ma之间的早白垩世。岩石地球化学研究表明:该组火山岩具有高硅、高钾、高Fe OT/Mg O比值(4.88~19.09),贫镁、钙特征,属高钾钙-碱性岩系;稀土元素表现为稀土总量较高(∑REE=82.02~436.61)、轻重稀土分馏明显(LaN/YbN=2.23~20.74)、属轻稀土富集型(LRE/HRE=2.71~11.87)、Eu负异常显著(δEu=0.06~0.42);微量元素特征表现为大离子亲石元素(LILE)Rb、Th、U、K相对较为富集,高场强元素(HFSE)Nb、Ta相对亏损,而Ba、Sr、Zr、Ti强烈亏损,与A2型花岗岩特征相似。其岩浆来源为典型的壳源岩浆系列,是陆壳岩石部分熔融的产物,形成于造山后的张性构造环境。 相似文献
4.
对胶东青山群中酸性火山岩进行了LA-ICP-MS锆石U-Pb同位素年代学研究。结果表明,3个粗面岩-粗面英安岩和1个流纹岩的年龄分别为119.4±0.9 Ma、118.2±1.0 Ma、120.2±0.9 Ma和120.0±0.8 Ma,都形成于早白垩世120~118 Ma之间。研究表明郯庐断裂带山东段及其两侧中生代青山群火山岩的年龄与苏皖段断裂带内火山岩的年龄相似,明显小于苏皖段断裂带附近火山岩盆地的火山岩年龄。其结果表明在中国东部岩石圈减薄的大背景下,受郯庐断裂控制的岩浆喷发事件持续的时间可能更长。胶东青山群中酸性火山岩表现出富钾、富碱、贫镁、贫钛和低Ni、Cr的地球化学特征,轻稀土元素富集,重稀土元素亏损。按地球化学组成可进一步分为粗面岩-粗面英安岩和流纹岩两类,前者富集大离子亲石元素Rb、Ba、K,亏损高场强元素Nb、Ta、Ti和P;而后者则强烈亏损Ba、Sr等大离子亲石元素和Ti、P等高场强元素。粗面岩-粗面英安岩相对流纹岩具有高的Sr和Ba含量以及La/Nb、Ba/Nb比值,而具有低的Rb/Ba比值和Eu负异常,说明它们来源于不同的岩浆源区。推测粗面岩-粗面英安岩可能是下地壳(俯冲扬子下地壳或者古老华北下地壳)部分熔融和富集地幔部分熔融混合的产物;流纹岩是由于区域拉张环境和高热异常背景下,下地壳发生深熔产生的岩浆喷出地表形成的,岩浆在上升过程中发生有分离结晶(大量斜长石的分离结晶)过程。 相似文献
5.
东昆中隆起带东段闪长岩U-Pb年代学和岩石地球化学研究 总被引：10，自引：5，他引：5
岩石学、岩石地球化学研究表明,东昆中隆起带东段分布一套高钾的钙碱性闪长岩系列岩石。岩石明显富集大离子亲石元素(如K、Ba、Rb)、LREE和活泼的不相容元素(如Th、U),相对亏损高场强元素(如Nb、Ta、Ti、P),具安第斯型活动大陆边缘岩浆岩特征。该闪长岩属混合成因,即由交代地幔的部分熔融形成基性岩浆,与地壳物质熔融形成的酸性岩浆混合形成。阿斯哈闪长岩LA-ICP-MS锆石U-Pb年龄值为244Ma左右,属印支早期。 相似文献
6.
澜沧江构造带中南段小定西组火山岩形成时代的厘定及其构造意义 总被引：2，自引：0，他引：2
三叠纪忙怀组、小定西组火山岩是澜沧江构造带中南段火山岩带的重要组成部分,是澜沧江古特提斯缝合带构造演化的产物。本文报道了小定西组巨厚玄武岩中安山岩和流纹岩夹层的岩石学、地球化学及锆石LA-ICP-MS年代学及Lu-Hf同位素特征。流纹岩锆石LA-ICP-MS U-Pb定年结果显示小定西组火山岩形成于230Ma。安山岩为高Al2O3的高钾钙碱性岩类,其较强的Nb、Sr和Ti负异常、较弱的Eu负异常、较低的Mg#、(La/Yb)N比值和Cr、Ni含量等特征与小定西组高铝玄武岩极为相似,说明安山岩岩浆与玄武岩岩浆来源相同或相似,是交代地幔物质部分熔融形成的玄武岩浆熔离分异的产物。流纹岩的过铝质特征,强烈Ba、Nb、Ta、Sr、P、Eu和Ti的负异常,与芒怀组流纹岩和临沧花岗岩极为相似,Nb/Ta、Th/Ce和Th/U比值与大陆地壳一致,以及εHf(t)值为-11.6~+9.6,峰值分布于-6.0~+2.0之间,对应的地壳模式年龄(tDM2)为658~1990Ma,大部分集中在1100~1600Ma范围内,反映其岩浆来源于中上地壳物质部分熔融的产物,并加入少量幔源组分的混合岩浆。小定西组玄武岩夹层中的安山岩和流纹岩都具有Rb、Ba、Th、U富集和Nb、Ta和Ti亏损,在微量元素构造环境判别图解上分布于陆缘弧或同碰撞岩浆岩区的特征。结合该区早三叠世地层缺失、晚三叠世磨拉石建造不整合覆盖在下伏地层之上,以及高压变质带的存在等分析认为澜沧江构造带中南段火山岩带中生代火山岩形成于同碰撞环境。在保山地块与印支地块碰撞过程中,交代地幔楔物质部分熔融形成的基性岩浆在上升过程中诱发地壳物质部分熔融形成酸性岩浆,下部基性和上部酸性两个岩浆房的岩浆间歇式喷发,形成下部以酸性火山岩为主(芒怀组),上部以基性火山岩为主(小定西组)的"双峰式"中三叠世火山岩带。 相似文献
7.
滇西晚始新世高镁富钾火山岩的地球化学特征及其岩石成因机制探讨 总被引：11，自引：0，他引：11
40Ar/39Ar同位素定年分析显示滇西新生代高镁富钾火山岩均形成于始新世晚期(约36 Ma),富含MgO(＞9%)和K2O(3.07%～7.28%),绝大部分K2O/Na2O比值大于2,均属超钾质系列岩石.较高的Cr、Ni含量和较低的Sc(＜30 μg/g)、TiO2(＜1%)含量暗示了源区为尖晶石相方辉橄榄岩;高镁富钾火山岩与区内同时代的粗面岩具相似的地球化学组成特征,均富集LILE和LREE,亏损高场强元素Nb-Ta和Ti等,具有极低的Nb/La比值(0.2～0.3)、较高的87Sr/86Sr初始值(0.7056～0.7072)、负的εNd初始值(-0.97～-4.87)和相对较高的206pb/204Pb(18.556～18.695)、207pb/204Pb(15.609～15.630)比值,具有明显的岛弧型钾质火山岩的性质.高镁富钾火山岩来源于受古特提斯俯冲带流体交代的尖晶石相方辉橄榄岩的部分熔融岩浆,并在深部岩浆房经历了橄榄石的结晶分异和堆晶作用,而粗面岩则还在相对浅部岩浆房经历了较大程度的长石与单斜辉石的分离结晶. 相似文献
8.
松辽盆地长岭断陷营城组火山岩的时代与岩石成因 总被引：1，自引：0，他引：1
对松辽盆地长岭断陷查干花次凹营城组火山岩进行了LA--ICP--MS U--Pb 年代学和岩石地球化学研究。确定研究区内火山岩形成于104 ～ 112 Ma 的早白垩世晚期。营城组火山岩主要由粗面岩、流纹岩、钠闪碱流岩、流纹质岩屑晶屑凝灰岩组成,化学成分显示均为流纹岩,属碱性系列。火山岩高硅富碱、贫铝钙镁; 铕负异常明显( δEu = 0. 16 ～ 0. 65) ,轻重稀土元素分馏较强［( La /Yb) N］ = 7. 15 ～ 10. 38; 富集大离子亲石元素K、Ｒb 和LＲEE。Ba、Sr 出现强烈的负异常,强烈亏损高场强元素P、 Ti,而Nb、Ta 并不亏损。该区中酸性火山岩由玄武质岩浆底侵导致新生地壳岩石部分熔融形成。 相似文献
9.
吉林平岗-渭津中性-中基性火山岩特征及成因 总被引：1，自引：0，他引：1
平岗-渭津中性-中基性火山岩的岩石化学特征显示:岩石类型主要有钾玄岩、玄武安山岩、安山岩、歪长粗面岩,岩浆系列以高K钙碱性系列为主,伴有钾玄岩系列和拉斑玄武岩系列;轻稀土富集,Eu异常不明显;Sr、K、Rb、Ba、Th等强不相容元素富集、高场强元素Nb相对亏损,反映出火山岩具火山弧与板内玄武岩构造背景的双重性.钾玄岩的Mg值及Ni含量表明钾玄岩属进化了的基性岩浆.根据Nd、Sr同位素比值及英安岩中辉石巨晶的结晶深度、松辽盆地东侧的地壳厚度等资料,认为钾玄岩浆来源于幔源基性岩浆.通过对岩浆密度及结晶压力、温度的估算认为多斑钾玄岩的形成与岩浆密度、斜长石密度及斜长石的结晶压力有关. 相似文献
10.
东昆仑高Nb-Ta流纹岩的年代学、地球化学及成因 总被引：8，自引：5，他引：3
东昆仑高Nb-Ta流纹岩位于东昆仑造山带东段,其锆石U-Pb年龄为213Ma,该时期东昆仑造山带正处于俯冲-碰撞造山阶段的晚期.与同时期东昆仑地区的其它酸性火山岩及世界其它处于俯冲-碰撞造山阶段的流纹岩相比较,这一套流纹岩显示高硅、高钾,低铝、低钙,高Nb、Ta及强烈亏损Sr、Eu的独特地球化学特征.东昆仑高Nb-Ta流纹岩的Sr、Nd同位素组成显示该流纹岩可能具有分别来源于地幔和上地壳的两个端元组分.通过讨论,本文认为这套高Nb-Ta流纹岩可能由以下机制形成:地幔碱性玄武岩浆(具有高Nb-Ta的特征)侵入花岗闪长质地壳,并在上地壳某处停留,大量斜长石发生分离结晶,导致岩浆Eu-Sr的极度亏损;同时,幔源岩浆的侵入引起上地壳围岩部分熔融,从而受到上地壳混染.新生壳源岩浆与幔源岩浆混合,并进一步结晶分异演化,最终导致东昆仑高Nb-Ta流纹岩的形成. 相似文献
11.
Petrological and geochronological constraints on high pressure, high temperature metamorphism in the Snowbird tectonic zone, Canada 总被引：7，自引：0，他引：7
The upper deck of the East Athabasca mylonite triangle (EAmt), northern Saskatchewan, Canada, contains mafic granulites that have undergone high P–T metamorphism at conditions ranging from 1.3 to 1.9 GPa, 890–960 °C. Coronitic textures in these mafic granulites indicate a near‐isothermal decompression path to 0.9 GPa, 800 °C. The Godfrey granite occurs to the north adjacent to the upper deck high P–T domain. Well‐preserved corona textures in the Godfrey granite constrain igneous crystallization and early metamorphism in the intermediate‐pressure granulite field (Opx + Pl) at 1.0 GPa, 775 °C followed by metamorphism in the high pressure granulite field (Grt + Cpx + Pl) at 1.2 GPa, 860 °C. U–Pb geochronology of zircon in upper deck mafic granulite yields evidence for events at both c. 2.5 Ga and c. 1.9 Ga. The oldest zircon dates are interpreted to constrain a minimum age for crystallization or early metamorphism of the protolith. A population of 1.9 Ga zircon in one mafic granulite is interpreted to constrain the timing of high P–T metamorphism. Titanite from the mafic granulites yields dates ranging from 1900 to 1894 Ma, and is interpreted to have grown along the decompression path, but still above its closure temperature, indicating cooling following the high P–T metamorphism from c. 960–650 °C in 4–10 Myr. Zircon dates from the Godfrey granite indicate a minimum crystallization age of 2.61 Ga, without any evidence for 1.9 Ga overgrowths. The data indicate that an early granulite facies event occurred at c. 2.55–2.52 Ga in the lower crust (c. 1.0 GPa), but at 1.9 Ga the upper deck underwent high P–T metamorphism, then decompressed to 0.9–1.0 GPa. Juxtaposition of the upper deck and Godfrey granite would have occurred after or been related to this decompression. In this model, the high P–T rocks are exhumed quickly following the high pressure metamorphism. This type of metamorphism is typically associated with collisional orogenesis, which has important implications for the Snowbird tectonic zone as a fundamental boundary in the Canadian Shield. 相似文献
12.
Anne M. Hofmeister Alan G. Whittington Maik Pertermann 《Contributions to Mineralogy and Petrology》2009,158(3):381-400
Thermal diffusivity (D) was measured using laser-flash analysis (LFA) from oriented single-crystal albite and glasses near LiAlSi3O8, NaAlSi3O8, CaAl2Si2O8, LiAlSi2O6 and CaMgSi2O6 compositions. Viscosity measurements of the supercooled liquids, over 2.6 × 108 to 8.9 × 1012 Pa s, confirm strongly non-Arrhenian behavior for CaAl2Si2O8, and CaMgSi2O6, and near-Arrhenian behavior for the others. As T increases, D
glass decreases, approaching a constant near 1,000 K. Upon crossing the glass transition, D decreases rapidly. For feldspars, D for the melt is ~15% below D of the bulk crystal, whereas for pyroxenes, this difference is ~40%. Thermal conductivity (k
lat = ρC
P
D) of crystals decreases with increasing T, but k
lat of glasses increases with T because heat capacity (C
P
) increases with T more strongly than density (ρ) and D decrease. For feldspars, k
lat for the melt is ~10% below that of the bulk crystal or glass, whereas this decrease for pyroxene is ~50%. Therefore, melting
substantially impedes heat transport, providing positive thermal feedback that could promote further melting. 相似文献
13.
14.
玄武岩及其高温高压相—榴辉岩的相组合,经历了长期的地质作用,反映出一定的时空条件。从高温高压实验矿物学,实验岩石学入手,对于以相组合出现的某些化学体系进行平衡条件研究,可揭示此类岩石形成的物理化学环境,并有助于阐明地球内部的物理状态、组成成分以及活动过程。 相似文献
15.
皖南绩溪县靠背尖高Ba-Sr花岗闪长斑岩年代学及其成因 总被引：10，自引：10，他引：0
皖南绩溪县靠背尖花岗闪长斑岩侵位于新元古代南华系、震旦系和下古生界海相沉积盖层中,岩石学、地球化学研究表明其为高钾钙碱性系列准铝质Ⅰ型斑岩体,稀土、微量元素及Sm-Nd、Rd-Sr同位素数据指示其主要来自地壳重熔,并有幔源物质的加入.异常高的Ba-Sr含量源于对区域早期富Ba-Sr岩浆岩物质的继承,幔源物质的加入使岩浆由S型转为Ⅰ型.微量元素构造判别图指示其形成于岛孤环境.三件样品锆石SHRIMP U-Pb测年得出的年龄加权平均值分别为151.9±1.1Ma、147.7±1.3Ma和152.7±1.1Ma,表明岩体侵位于晚侏罗世.靠背尖岩体受后期热液影响广泛发育钾化、硅化等高温蚀变,并可能有高温条件的韧性变形,因此前人报道的黑云母40Ar/39 Ar年龄134.3±1.4Ma可能代表构造热事件的年龄. 相似文献
16.
M. D. Watts 《Australian Journal of Earth Sciences》2013,60(3):229-234
An intense Bouguer anomaly ‘high’ of about 30 milligals amplitude has been delineated to the east of Cootamundra, New South Wales. It is correlated with a north‐trending belt of basic metamorphic rocks of probable Upper Silurian age. The subsurface shape of the belt is deduced by qualitative and quantitative analytical techniques applied to the gravity data; it is inferred that the boundary on the western side is near‐vertical, while that on the eastern side is believed to have been overthrust by the Middle Devonian Young Granite. It appears also that there are no horizontal density variations below a depth of 6–7 km, implying that the base of the Young Granite lies at about this depth. 相似文献
17.
Eiji Ohtani Naohisa Hirao Tadashi Kondo Masayoshi Ito Takumi Kikegawa 《Physics and Chemistry of Minerals》2005,32(1):77-82
We observed a direct reaction of metallic iron with water to form iron hydride and iron oxide, 3Fe + H2O–>2FeHx + FeO, at pressures from 6 GPa to 84 GPa and temperatures above 1,000 K in diamond anvil cell (DAC). Iron hydride is dhcpFeHx or -FeHx, and iron oxide has the rhombohedral or B1 structure at pressures at least up to 37 GPa. The formation of an assembly composed of dhcpFeHx and FeO with the B8 structure was observed at 84 GPa. In primordial Earth, water formed by dehydration of the low temperature primitive materials reacts with metallic iron in the high temperature component to form iron hydride FeHx and iron oxide FeO. The former would be incorporated in the iron forming the core. Thus hydrogen could be an important element of the Earths core. This reaction would be essential for transport of hydrogen into the core in the accretion stage of the Earth. 相似文献
18.
S. Merkel A. P. Jephcoat J. Shu H.-K. Mao P. Gillet R. J. Hemley 《Physics and Chemistry of Minerals》2002,29(1):1-9
Physical properties including the equation of state, elasticity, and shear strength of pyrite have been measured by a series
of X-ray diffraction in diamond-anvil cells at pressures up to 50 GPa. A Birch–Murnaghan equation of state fit to the quasihydrostatic
pressure–volume data obtained from laboratory X-ray source/film techniques yields a quasihydrostatic bulk modulus K
0T
=133.5 (±5.2) GPa and bulk modulus first pressure derivative K
′
0T
=5.73 (±0.58). The apparent equation of state is found to be strongly dependent on the stress conditions in the sample. The
stress dependency of the high-pressure properties is examined with anisotropic elasticity theory from subsequent measurements
of energy-dispersive radial diffraction experiments in the diamond-anvil cell. The calculated values of K
0T
depend largely upon the angle ψ between the diffracting plane normal and the maximum stress axis. The uniaxial stress component
in the sample, t=σ3−σ1, varies with pressure as t=−3.11+0.43P between 10 and 30 GPa. The pressure derivatives of the elastic moduli dC
11/dP=5.76 (±0.15), dC
12/dP=1.41 (±0.11) and dC
44/dP=1.92 (±0.06) are obtained from the diffraction data assuming previously reported zero-pressure ultrasonic data (C
11=382 GPa, C
12=31 GPa, and C
44=109 GPa).
Received: 21 December 2000 / Accepted: 11 July 2001 相似文献
19.
冀西北万全地区大麻坪地幔岩包体高温高压弹性波研究及其地质意义 总被引：1，自引：0，他引：1
对河北大麻坪碱性玄武岩及其内的辉石岩和二辉橄榄岩包体进行了不同温压条件下的弹性波速测定。结果表明,岩石波速与压力正相关,与温度负相关;相同条件下二辉橄榄岩的弹性波速最大,辉石岩次之,玄武岩最小。在1.4GPa压力下获得二辉橄榄岩和辉石岩的弹性波速分别为7.87km/s和7.47km/s,最接近壳幔过渡带的弹性波速。而现代地球物理资料显示该地区莫霍面深度为32km,认为26Ma以来,该地区发生了大规模的岩石圈减薄地质事件。 相似文献
20.
Damage and conservation of the high cliff on the Northern area of Dunhuang Mogao Grottoes, China 总被引：2，自引：1，他引：1
The Mogao Grottoes have 750 caves, 45,000 m2 of wall paintings, 2,415 painted sculptures, five wooden temple fronts from the Tang and Song dynasties, and thousands of
columns with carved designs of lotus flowers and ornamental tiles. The Mogao Grottoes are one of the largest and best-preserved
Buddhist art treasure houses in the world. The diverse range of wall paintings and sculptures and the profound and varied
Buddhist art at the site prompted UNESCO to list the grottoes as a World Heritage Site for its cultural values. The Mogao
Grottoes consist of two areas: the Southern Grottoes Area and the Northern Grottoes Area. Almost all the Buddhist art treasures
are located in the southern area. The northern area is mainly where the monks and the creators of the arts of Dunhuang resided.
In this paper, the causes of damage to the grottoes are analyzed by investigating the geohazards occurring on the side slopes
on the high cliff in the northern zone. This paper will analyze the causes of deterioration through the investigation of deterioration
in the upper section of the cliff face and goes on to discuss the main causes of deterioration of the cliff body: the development
of fissures, wind erosion, rain erosion, and flood scouring. The following measures have been undertaken to deal with the
above problems: bolt anchoring, grouting of fissures, use of bracing supports in some areas, and stabilization of caves and
cliff face. Through the above measures, the upper section of the upper face in the northern zone has been effectively treated
according to the principles of “restoration to historic condition and not altering the historic appearance.” 相似文献