大麻坪橄榄石冲击波实验研究与高压态物态方程参数的确定

利用冲击波进行的动高压实验对研究超高压下的物质性质也是十分有效的.本文报告了对大麻坪采集的橄榄石进行压力在10~45GPa范围的冲击波动高压实验结果.结合前人等温冷压实验结果,确定了实验过程的温度,对于冲击波实验压力从10GPa变化到30GPa时,温度在摄氏几十度到摄氏800多度之间.测量了岩石超高压下密度变化,在3.627~4.009g·cm~(-3)之间.通过回收实验和确定的温度,表明小于30GPa压力实验条件下,没有发生相变过程.同时也确定了状态方程的参数.最后,指出了实验结果在上地幔地球内部物质运动过程的含义,即冷板块中的亚临界橄榄岩可以存在地幔转换带中.     

华北地区四种岩石在高压下的破坏特征

利用我国第一台1GPa高压三轴容器进行了岩石破坏实验.所用的样品为济南辉长岩、昌平花岗岩、房山大理岩和周口店石灰岩.得到的主要结果是:(1)在相应于地壳的压力范围内辉长岩和花岗岩仍然发生脆性破坏, 其强度和韧度随围压增加而增加, 破坏角也随围压增加而增大, 破坏前发生体积膨胀现象并出现声发射活动增加的前兆;(2)大理岩和石灰岩样品在0.1——0.8GPa的围压范围内发生鼓状变形, 不形成明显的主断层面, 样品承载能力随变形增加而增加, 出现应变硬化现象.在变形过程中声发射活动水平极低。这些实验标志着我国岩石力学三轴实验的围压水平有所提高其结果对震源物理的研究具有参考价值.      

新疆东准噶尔花岗岩类岩石高温高压弹性波速度及其对地壳结构的约束

应用超声波反射-透射法,在最高压力为1.0 GPa（室温）,最高温度为700℃（1.0 GPa）的条件下对新疆东准噶尔地区的卡拉麦里花岗岩带和野马泉岩体的典型花岗岩类岩石（碱长花岗岩、碱性花岗岩、花岗闪长岩、二长花岗岩和石英闪长岩）的纵波速度（V_P）和横波速度（V_S）进行了测量.结果显示,在常温、压力0.4~1.0 GPa条件下,东准噶尔地区花岗岩类岩石的V_P和V_S均随压力呈线性增加,说明在这个压力段岩石中的微裂隙已基本闭合.室温、1.0 GPa时花岗岩类岩石的V_P是5.79~6.84 km·s^-1,V_S是3.26~3.85 km·s^-1.依据压力与V_P及压力与V_S的线性关系,拟合得到常温常压下花岗岩类岩石的纵波和横波压力系数分别是0.1568~0.4078 km/（s·GPa）和0.0722~0.3271 km/（s·GPa）,V_P0和V_S0分别是5.62~6.47 km·s^-1和3.15~3.75 km·s^-1.恒压1.0 GPa、室温到700℃条件下,花岗岩类岩石的V_P和V_S均随温度的升高呈线性降低,温度系数分别为（-3.41~-4.96）×10^-4 km/（s·℃）和（-0.88~-3.22）×10^-4 km/（s·℃）.利用实验获得的花岗岩类岩石的V_P0、V_S0及温度系数和压力系数,结合东准噶尔地区的地热资料,建立了V_P和V_S随深度变化的剖面.将获得的V_P和V_S-深度剖面与该区地球物理探测结果对比,发现东准噶尔地区的碱长花岗岩、碱性花岗岩、二长花岗岩和部分花岗闪长岩的V_P和V_S与该区上地壳速度吻合很好,同时这几种岩石的平均泊松比也与上地壳泊松比一致,因此我们认为这几种类型的岩石是该区上地壳的重要组成部分.另外,石英闪长岩的V_P和V_S均符合中地壳的速度,可能为中地壳中的一种岩石.     

阿尔金超高压(>7 GPa)片麻状(含)钾长石榴辉石岩

岩相学和矿物化学研究表明, 阿尔金英格利萨依一带片麻状(含)钾长石榴辉石岩中的粗粒石榴子石出溶单斜辉石和金红石. 统计石榴子石出溶的单斜辉石的面积比最高>5%, 重建出溶前该石榴子石(Grt1)单位分子式中的Si值高达3.061, 为含Na的超Si-石榴石或含有majorite分子的石榴子石. 依据石榴子石含辉石摩尔体积压力计和majoritic-石榴子石 Si-(Al+Cr)压力计估算其峰期变质压力>7 GPa, 利用三元碱性长石温度计和钛铁矿-磁铁矿固溶体的实验资料获其形成温度约1000℃. 同时, 结合其原岩具有板内基性与中性火成岩及其可能是源于大陆岩石圈地幔的基性岩浆演化产物的地球化学特征, 以及与其伴生的超高压石榴子石二辉橄榄岩的发现和超高压含石榴子石花岗质片麻岩的研究, 不仅证明区内超高压岩石的形成是陆壳深俯冲作用的产物, 而且表明这种深俯冲可能达到>200 km的地幔深处. 这对深入探讨阿尔金乃至中国西部碰撞造山带形成与演化的动力学机制提供了新的证据.     

秦岭-大别造山带根部超高压变质岩隆升的岩石学证迹

岩相学证据表明大别山区超高压榴辉岩是绿帘角闪岩相岩石经超高压变质而成;碰撞造山峰期超高压变质之后,由于造山带的演化,地体隆升,超高压榴辉岩普遍表现近等温减压退变质,经高压榴辉岩相至角闪岩相,然后降温降压为绿帘角闪岩相及绿片岩相,有些超高压岩石则通过等压冷却过程达绿帘蓝片岩相而后降压降温为绿片岩相,随着退变质作用的进行,岩石经历多期变形可识别出6个世代,从塑性到脆性。减压P-T轨迹亦见于流体包裹体的演化,捕获压力可从2.05GPa近等温减压至<1.0GPa,含盐度显著降低,流体的Br/Cl和I/Cl比高于海水和全球平均值,说明流体来源是深部变质水。     

孔隙、裂隙介质弹性波理论的实验研究

近年来发展起来的“孔隙、裂隙介质弹性波理论”提高了人们对实际岩石声学性质的模拟和预测的能力.作为对这一理论的实验验证和重要应用,我们将它用来模拟和解释岩石超声实验中测得的干燥和饱和岩石弹性波速度随压力的变化曲线.理论模拟的重要参数,如岩石的裂隙密度等是从实验数据反演得到的.结果表明：无论是孔隙度较高的砂岩,还是孔隙度很小的致密岩石,如花岗岩,该理论都能很好地描述岩石在干燥和饱和状态下纵、横波速度随压力的变化.造成波速变化的原因是岩石中裂隙在压力作用下的闭合和裂隙密度的减少.本文的结果还指出了将岩石裂隙密度作为描述岩石的重要物性参数,并给出了从实验室超声测量中确定这一参数的方法.     

阿尔金英格利萨依花岗质片麻岩超高压变质

岩相学和矿物化学研究显示, 阿尔金英格利萨依一带含石榴子石花岗质片麻岩经历了复杂多阶段的变质演化, 其早期变质矿物组合是Grt+Per(出溶前)+Tit(出溶前)+Ky+Zoi+Qz/Coe±Cpx, 副矿物为Ap和Ru, 其中粗粒榍石含有斜长石＋角闪石的棒状出溶物, 计算的榍石出溶前(Tit)的成分含六次配位的Si^Ⅵ, 单位分子式中Si值介于1.032~1.047之间, 即含CaSi₂O₅组分为3.1%~4.6%. 利用实验岩石学资料和三元碱性长石温度计, 获早期变质条件为3.7~4.3 GPa和约1000℃, 结合石榴子石包裹的高Al-榍石,共同证实该岩石经历了超高压变质. 岩石化学特征显示, 该片麻岩的SiO₂含量>70%, Al₂O₃含量为12.58~14.08%, K₂O含量很高(>5%), Na₂O/K₂O比值介于0.4~0.6之间, 稀土配分呈LREE富集型, (La/Yb)N比值介于4.3~9.1之间, 具有明显的负Eu异常(δEu=0.06~0.59), 其原岩可能为中、上地壳重熔的产物. 同时, 考虑与其呈互层状或间层状产出的石榴子石二辉橄榄岩和含石榴子石中基性片麻岩都经历了超高压变质的研究成果, 共同证实区内超高压岩石的形成是陆壳深俯冲作用的产物, 这对深入探讨区内超高压岩石形成与折返的动力学机制提供了重要的约束.     

哀牢山变质带元江──墨江剖面岩石的纵波波速特征及其地质意义

依据研究区的地热梯度（25℃／km）,在高温高压（最高温度为1050℃,最高压力为1.2GPa）条件下系统测量了横穿红河-哀牢山断裂带的元江-墨江地质剖面上的哀牢山岩群各类变质岩（千枚岩、片岩、浅粒岩、变粒岩、大理岩和片麻岩）的纵波速度．实验结果表明,不同岩类的纵波速度随温度压力变化的趋势不同．在相当于衷牢山岩群变质岩峰期变质温度和压力条件下（P=0．4-0.8GPa,T=35-700℃）,测得大部分岩石的纵波速度为5．50－5．80km／s,这一纵波速度值与区域地球物理测深揭示的中地壳低速层的纵波速度相当因此,结合该区变质岩、地壳内热状态及地球物理测深研究成果可初步认为：组成哀牢山岩群的浅粒岩、变粒岩、酸性片麻岩以及部分千枚岩、片岩为该地区中地壳低速层的主要岩石类型．     

大别山双河超高压变质岩及北部片麻岩的U-Pb同位素组成

大别山超高压变质岩及各种片麻岩的U-Pb同位素地球化学研究表明, 出露于大别山南部的超高压变质岩具有较低的Pb含量(多数<4 mg/g)和较高的U/Pb比(多数>0.1), 以及较大的Pb同位素变化范围和较高的放射成因Pb(206Pb/204Pb = 16.535～ 20.405). 它们表现出在俯冲过程中经历了脱水、析出流体和Pb丢失过程及地幔Pb与上地壳岩石Pb混合的Pb同位素特征. 然而出露于大别山北部的片麻岩具有较高的Pb含量(多数 > 4 mg/g)和较低的U/Pb(<0.07)以及较低的Pb同位素比值(206Pb/204Pb = 15.781～16.647), 并与侵入南、北大别山的中生代花岗岩的Pb同位素特征相同. 它们表现出在俯冲过程中仅有少量流体析出和Pb丢失以及地幔Pb与下地壳Pb混合的同位素特征. 这些样品在230 Ma前的初始Pb同位素组成还表明南大别带超高压岩石的U/Pb比在大陆俯冲前很长一段时期内比北大别带片麻岩高. 这些观测表明南大别带出露的超高压岩石主要是深俯冲的上地壳岩石, 而北大别带具有中、下地壳的性质. 据此, 本文提出了在大陆深俯冲过程中, 俯冲陆壳拆离成若干岩片, 深俯冲的超高压上地壳岩片有可能沿断层逆冲到较浅部位的超高压岩石折返机制模型.     

差应力在超高压变质岩形成过程中的作用——来自石英-柯石英转化的高温高压实验证据

文中概述了超高压变质岩在静水压条件下的形成温压范围和存在的问题 ,并重新整理和分析了Hirth等 (1994 )在差应力条件下石英向柯石英转化的高温高压实验数据。结果表明 ,存在较大差应力的条件下柯石英出现需要的围压 (1 2 0～ 1 2 5GPa) ,远小于静水压下的围压 (2 5～ 3GPa) ,显然差应力的影响是显著的。榴辉岩中部分石榴石存在塑性变形 ,这表明在碰撞造山的构造环境中构造差应力是客观存在的 ,而构造差应力的上限受岩石强度制约。因此 ,差应力在超高压变质岩的形成过程中起到了重要作用 ,而系统地进行高温高压实验研究是深入探讨这一问题必要而有效的方法之一     

The experimental study of parameters of rocks under ultrahigh-pressure state

The parameters of rocks in ultrahigh-presure state are very important to understanding the geodynamics and explosion engineering of rocks. In these experiments the plane wave dynamite lenses were used to drive the flying plates. The flying plate hits the target and produces the ultrahigh-pressure shock wave. The propagation velocity and the particle velocity of shock wave in rock samples were measured by probes, and the relation between density of rocks and pressure was obtained by Rankine-Hugoniot formulas. The maximum pressure in experiments was higher than 70 GPa. The ultrahigh-pressure state formulas obtained are: Limestoneρ=3.22+0.016p; Graniteρ=3.20+0.024p. In which the unit for ρ is g/cm³, the unit forp is GPa. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,13, 96–103, 1991.     

Hugoniot equation of state of olivine and its geodynamic implications

Large olivine samples were hot-pressed synthesized for shock wave experiments. The shock wave experiments were carried out at pressure range between 11 and 42 GPa. Shock data on olivine sample yielded a linear relationship between shock wave velocity D and particle velocity u described by D=3.56(?0.13)+2.57(?0.12)u. The shock temperature is determined by an energy relationship which is approximately 790°C at pressure 28 GPa. Due to low temperature and short experimental duration, we suggest that no phase change occurred in our sample below 30 GPa and olivine persisted well beyond its equilibrium boundary in metastable phase. The densities of metastable olivine are in agreement with the results of static compression. At the depth shallower than 410 km, the densities of metastable olivine are higher than those of the PREM model, facilitating cold slab to sink into the mantle transition zone. However, in entire mantle transition zone, the shock densities are lower than those of the PREM model, hampering cold slab to flow across the "660 km" phase boundary.     

Metamorphism, partial preservation, and exhumation of ultrahigh-pressure belts

The Dabie-Sulu belt of east-central China, the Kokchetav Complex of northern Kazakhstan, the Maksyutov Complex of the South Urals, the Dora Maira Massif of the Western Alps, and the Western Gneiss Region of southwestern Norway lie astride intracontinental suture zones. All represent collisional mountain belts. Adjoining Eurasian regions exhibit little or no evidence of a coeval calc-alkaline arc. Each metamorphic complex contains mineralogic and textural relics of the presence or former existence of coesite ± diamond. Other ultrahigh-P, moderate-T metamorphic phases, including K-rich clinopyroxene, Mg-rich garnet, ellenbergerite, lawsonite, Al-rutile, glaucophane, high-Si phengite, and associations such as coesite + dolomite, magnesite + diopside, and talc + kyanite, diopside, jadeite, or phengite also testify to pressures approaching or exceeding 2.8 GPa. Each of the five well-studied Eurasian ultrahigh-pressure complexes consists chiefly of old, cool continental crust. Deep-seated recrystallization took place during the Phanerozoic. Subduction zones constitute the only known plate-tectonic environment where such high-P, low-T conditions exist. A model involving underflow of a salient of continental crust imbedded in oceanic crust-capped lithosphere explains the ultrahigh- pressure metamorphism. Partly exhumed ultrahigh-pressure terranes consist of relatively thin sheets 7 ± 5 km thick. During early stages of plate descent, hydration of relatively anhydrous units occurs, and volatiles are expelled from hydrous rocks. If present, aqueous fluids markedly catalyze reactions. Experimental studies on MORB bulk compositions demonstrate that, for common subduction-zone P–T trajectories, amphibole (the major hydrous phase in metabasaltic rocks) dehydrates at less than ~ 2.0 GPa; accordingly, mafic blueschists and amphibolites expel H₂O at great depth and, except for some coarse-grained, dry metagabbros, tend to recrystallize to eclogite. Serpentinized mantle beneath the oceanic crust devolatilizes at comparable pressures. In contrast, phengite and biotite remain stable to pressures exceeding 3.5 GPa in associated quartzofeldspathic rocks. So, under ultrahigh-pressure conditions, the micaceous lithologies that dominate the continental crust fail to evolve significant H₂O, and may transform incompletely to eclogitic assemblages. Although hydrous rocks expel volatiles during compaction and shallow burial, very deep underflow of partly hydrated oceanic crust + mantle generates most of the volatile flux along and above a subduction zone prior to continental collision. As large masses of sialic crust enter the convergent plate junction, fluid evolution at deep levels severely diminishes, and both convergence and dehydration terminate. After cessation of ultrahigh-pressure recrystallization, tectonic slices of sialic massifs return to shallow depths along the subduction channel, propelled by buoyancy; collisional sheets that retain ultrahigh-pressure effects lose heat efficiently across both upper (extensional, normal fault) and lower (subduction, reverse fault) tectonic contacts. These sheets ascend to midcrustal levels rapidly at average exhumation rates of 2–12 mm/year. Surviving ultrahigh-pressure relics occur as micro-inclusions encased in dense, strong, impermeable, unreactive mineralogic hosts, and are shielded during return towards conditions characteristic of midcrustal levels. Rehydration attending decompression is incomplete; its limited extent reflects the coarse grain size and relative impermeability of the rocks undergoing retrogression, as well as declining temperature and lack of aqueous fluids.     

10.6～1.5GPa、室温～1 200℃条件下青藏高原地壳岩石弹性波速特征

通过对采自青藏高原的六种地壳岩石，包括花岗闪长岩、混合岩、片麻岩、玄武岩、辉橄岩及斜长角闪岩等，进行高温高压纵波速度测量，发现绝大多数地壳岩石其纵波速度在压力高于0.2-0.3GPa时基本上随压力线性增加。在固定压力下随温度升高而降低，但在温度较低时这一现象并不明显，随温度的程式高波速出现明显降低。通过对实验后的样品进行显微薄片分析，发现含水矿物的脱水和部分熔融是造成岩石波迅速降低的主要原因。在实验过程中还发现高压下温度较高时，接收到的超声波振幅会增大。对实验中发现的这些现象本文进行了初步的分析和讨论。     

汶川地震破裂带断层岩纵波速度与孔隙度关系的实验研究

分布于地震破裂带上的断层岩具有高孔隙度的特征.该特点造成了其弹性波速度与结晶岩石和沉积岩存在明显的差异.确定断层岩的弹性波速度与孔隙度和矿物组成的关系对于利用地震资料探测深部断层和测井资料的解释至关重要.在10~600 MPa条件下,本文对地震断层岩的纵波波速（V_p）和总孔隙度（φ_t）进行了测量,并深入分析了V_p与孔隙度的关系.结果表明在10~600 MPa的压力范围内,V_p（p）随着压力的增高呈现对数增加,其增长率随着压力的上升而逐渐减小,遵从∂V_p（p）/∂p=a_v/p的变化规律.断层岩中的孔隙度随着压力的增高呈对数减小.与传统的认识不同,实验发现在压力高达600 MPa以上,大多数断层岩中仍然可以残留可观的孔隙量.分析显示V_p与总孔隙度及总粘土含量呈负线性相关.该发现有助于认识深部流体的活动通道特征,有助于理解断层带中存在大量粘土矿物、断层带内的物质可被大量带出、围陷波的形成等地质和地球物理现象.     

华北地区典型岩石在1万巴压力下的密度和弹性波速度的实验研究s

利用高压三轴容器,对华北地区九种典型岩石的密度和弹性波速度随压力的变化关系进行了实验研究。实验的最高压力达到10,500巴。实验中利用电阻应变片测量岩石的体积变化从而得到密度的变化。用高频脉冲法测量了弹性波速度。由得到的密度参数和波速参数计算出高压下岩石的声阻抗。根据体应变和波速随压力变化的曲线估算了岩石的体积模量,裂纹孔隙度,裂纹闭合压力,波速达到稳定变化时的压力以及波速达到稳定变化时的值与常压下的波速值的差。对这些参数在地学及爆破工程上的应用进行了简单的讨论。      

不同温压条件下弹性波在岩石中传播速度的实验研究

对以岩浆岩为主的岩石类型进行了不同温压条件下弹性波传播速度的实验研究，结果表明：（１）岩石的物质组成是决定弹性波传播速度的主要因素。以岩浆岩为例，由酸性到基性波速呈增加趋势；（２）岩石中弹性波的传播速度随环境条件改变而变化。一般说来，随温压条件的升高而升高     

Diamond-bearing and diamond-free metacarbonate rocks from Kumdy–Kol in the Kokchetav Massif, northern Kazakhstan

Abstract Dolomite marble from the Kumdy–Kol area of the Kokchetav Massif contains abundant microdiamond, mainly in garnet and a few in diopside. The mineral assemblage at peak metamorphic condition consists of dolomite + diopside + garnet (+ aragonite) ± diamond. Inclusions of very low MgCO₃ calcite and almost pure calcite occur in diopside and are interpreted as aragonite and/or aragonite + dolomite. Single-phase Mg–calcite in diopside with a very high MgCO₃ component (up to 21.7 mol%) was also found in diamond-free dolomitic marble, and is interpreted as a retrograde product from aragonite + dolomite to Mg–calcite. The dolomite stability constrains the maximum pressure (P) at < 7 GPa using previous experimental data, whereas the occurrence of diamond yields the minimum peak pressure–temperature (P–T) condition at 4.2 GPa and 980 °C at X co ₂ = 0.1. The highest MgCO₃ in Mg–calcite constrains the minimum P–T condition higher than 2.5 GPa and 800 °C for the exhumation stage. As these marbles were subjected to nearly identical P–T metamorphic conditions, the appearance of diamond in some carbonate rocks was explained by high X co ₂. A low X co ₂ condition refers to high oxidized conditions and diamond (and/or graphite) becomes unstable. Difference in X co ₂ for marble from the same area suggests local heterogeneity of fluid compositions during ultrahigh-pressure metamorphism.