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51.
Ultrahigh-pressure (UHP) eclogites often show strong plastic deformation and anisotropy of seismic properties. We report in this paper the seismic velocity and anisotropy of eclogite calculated from the crystallographic preferred orientations (CPOs) of constituent minerals (garnet, omphacite, quartz and rutile) and single crystal elastic properties. We also compared the calculated results with the measured results in similar eclogites. Our results suggest that (1) Except that garnet is a seismically quasi-isotropic mineral, omphacite, quartz, coesite and rutile all have strong seismic anisotropies (AVp = 23.0%―40.9%, Max. AVs = 18.5%―47.1%). They are the major sources for anisotropy in eclogite. The average seismic velocities are fast in garnet and rutile, moderate in omphacite and coesite, and slow in quartz. (2) The deformed eclogites have the maximum Vp (8.33―8.75 km/s) approximately parallel to foliation and lineation, the minimum Vp (8.25―8.62 km/s) approximately normal to foliation and lineation and the Vp anisotropies of 1.0―1.7%. Their Vs are 4.93―4.97 km/s. The corresponding maximum anisotropies (0.73%―1.78%) of Vs are at 45° to both foliation and lineation and the minimum anisotropies at positions normal to lineation on the foliation plane. The Vs1 polarization planes are approximately parallel to foliation. The mean Vp and Vs of eclogite under UHP peak metamorphism conditions (P = 3―5 GPa, T = 900―1100℃) are estimated to be 3.4%―7.2% and 6.3%―12.1% higher than those at ambient pressure and temperature conditions, respectively. (3) Omphacite component dominates the anisotropy of eclogite while garnet component reduces the anisotropy and increases the seismic velocities. Quartz component has a small effect on the anisotropy but reduces the seismic velocities of eclogite. The effect of rutile component is negligible on seismic properties of eclogite due to its trivial volume fraction. (4) The increase of volume fraction of omphacite in eclogite will reduce the seismic velocities and increase the anisotropy. Omphacitite has seismic velocities reduced by 6%―8% and anisotropies increased to 3%―4% compared to those of garnetite. Our results suggest that the seismic properties calculated with single crystal elastic properties and CPOs are equivalent to those measured in laboratory. Moreover, it provides insights into the mineral physical interpretations of eclogite seismic properties. 相似文献
52.
依据海洋法确定的管辖海域对沿海国的管理有着法律意义.海警在我国管辖海域内执法,尤其是处理涉外案件,不仅要依照国内法律、法规、规章,而且必然受到海洋法的影响. 相似文献
53.
地震勘探是地球物理和油气勘探的重要手段之一,近年来逐渐向更深地层更精细化的方向发展,传感器节点数和数据量也变得更加庞大,同时数据分析端对数据质量的要求却更高,这要求海量节点上的数据要快速准确地上传到数据储存服务器,其中实现实验数据的高速可靠传输成为系统设计的一个关键难点.针对地球物理勘探和油气勘探的特点,本文提出了一种应用于大规模地震勘探仪器数据传输系统的高可靠传输协议,既能提高整个数据获取系统的稳定性同时又能提高数据的可靠性.该协议通过对数据传输过程中产生的错误采取充分的检测和处理算法,使得传输错误不会影响到系统的正常运行而且有效数据能正确地上传,并结合DAQ（Data Acquisition,数据获取系统）实现数据存储的容错机制,有效提高了系统稳定性和物理实验数据的可靠性,极大提升了地球物理勘探的工作效率. 相似文献
54.
HuaYong Li HuCai Zhang FengQin Chang Qian Zheng WenXiang Zhang GuoLiang Lei YanBin Lei Yang Pu JunFeng Ji 《中国科学:地球科学(英文版)》2017,60(12):2171-2180
Lake Zigetang is located on the central Tibetan Plateau (TP) and represents a rare but typical meromictic lake in China. The lake’s stable meromixis sustains microflora communities, and changes in these communities are relatively independent of climate. Therefore, these communities can be used as paleoclimate proxies. In this paper, the stratification properties and their relationships with the microflora of Lake Zigetang were analyzed. We found that water depth and climate conditions were two important factors for maintaining meromixis in Lake Zigetang. Generally, stratification was enhanced during warm periods, while temperature differences between the mixolimnion and monimolimnion were decreased during cold periods. The presence of anoxygenic phototrophic bacteria (APB) was demonstrated by the discovery of bacteriopheophytin-a (Bph-a) in the sediments. This bacterial community is mainly concentrated at the bottom of the chemocline and the top of the monimolimnion, where it forms a thin APB layer. Moreover, total APB productivity is mainly affected by the light intensity penetrating to the APB layer, which exponentially increases as the thermocline becomes shallow. Therefore, high Bph-a values in the lake corresponded to a shallow thermocline and warm periods, low Bph-a values corresponded to cold periods, and zero changes indicated that the water was completely mixed and reflected an extreme cold climate or low lake level period. Thus, Bph-a can be used as a climate proxy to reconstruct the history of lake stratification and climate changes. 相似文献
55.
秦岭拉鸡庙镁铁质岩体锆石LA-ICP-MS年代学研究 总被引：10，自引：7，他引：3
秦岭拉鸡庙镁铁质岩体位于北秦岭南缘,主要由辉长岩(80%)、苏长辉长岩(15%)和少量闪长岩等侵入杂岩组成。对采自该岩体闪长岩的锆石进行阴极发光图像、微区原位LA-ICP-MS微量元素分析和U-Pb定年。CL图像显示这些锆石可以分为两类,一类锆石呈长柱状,具有明显的岩浆生长环带;另一类则呈浑圆状,阴极发光图像复杂,部分颗粒岩浆生长环带较模糊,个别样品外围存在一窄的亮色环边,推测为后期地质事件影响的结果。对26颗锆石核部和生长边进行28次U-Pb同位素分析,获得两组206Pb/238U年龄,分别为973±60Ma和422±7Ma。分析结果显示,所有样品具有高的Th, U, REE含量,明显富集HREE,其Th/U比值普遍高于0.6,表明这些锆石应属于岩浆成因。其中,422±7Ma应该代表拉鸡庙镁铁质岩体的成岩时代,这可能与古生代扬子陆块或者是具有扬子板块属性的微陆块和华北陆块的碰撞有关,该碰撞导致了秦岭洋的闭合;而973±60Ma应为捕获锆石年龄,代表北秦岭早期与Rodinia超大陆拼合有关的岩浆事件。考虑到没有检测到典型的华北克拉通的年龄,推测元古代北秦岭更接近华南板块。 相似文献
56.
扬子地块与南秦岭造山带的盆山系统与构造耦合 总被引：12，自引：3，他引：9
本文重新厘定了扬子地块西北缘晚古生代至早中生代沉积盆地的原型,在综合分析南秦岭造山带和勉略缝合带形成规律的基础上,对于南秦岭造山带与扬子地块北缘的拼合演化历史以及盆山耦合关系进行了研究。指出在晚二叠世晚期(长兴组沉积上段)和早三叠世早期(飞仙关组沉积下段)发生点式碰撞,在两个不同的大地构造单元之间形成了与碰撞相关的裂谷盆地群(包括开江-梁平裂谷、城口-鄂西裂谷和东部的当阳裂谷等),碰撞裂谷群的持续演化时间为5~6Ma,这一阶段典型的沉积标志为水下早期阶段形成的海相磨拉石层序。至早三叠世的嘉陵江二段沉积时期,两个不同地块的持续拼合导致大巴山和米苍山地区与周缘前陆盆地相关的古冲断带的形成,该阶段在缝合带接触部位发育角度不整合和河流相沉积,扬子地块其余大部仍然是保持连续的海相碳酸盐岩沉积。晚三叠世南秦岭造山带与扬子北缘之间的残余大洋消失,为整体闭合的碰撞后期阶段,沉积了须家河组开始的陆相碎屑岩系,大巴山和米苍山地区进入到了以陆相磨拉石为主的前陆盆地阶段,在扬子北缘形成了神农架-黄陵隆起和米苍山隆起。晚三叠世以后大巴山和米苍山地区进入了比较复杂的后期改造阶段,产生了多期的收缩性构造活动,包括以形成区域性的假整合和小角度不整合为特征的晚侏罗世-早白垩世早期(J3-K1)的低幅度活动期;以大巴山和米苍山冲断带的强烈改造为主,形成薄皮冲断构造系统的早白垩世晚期变形和以形成大巴山弧形冲断带和米苍山基底卷入的冲断带为特征的新生代晚期变形。 相似文献
57.
Stratified flow is common for the gravity segregation and flow regimes are very complex because of borehole inclination, therefore, all the conventional production logging tools cannot be effectively applied in horizontal wells, thus significantly increasing the difficulties in log interpretation. In this paper, firstly, the overseas progress in updated integration tools for horizontal wells and production profile interpretation methods has been discussed in brief. Secondly, by means of theory study and experimental simulations, we have obtained the production profile interpretation model and experimental interpretation charts, which have been calibrated by the improved downhole technology and optimization methods. Finally, we have interpreted X-well with the production profile interpretation software designed by us, and it proves that the methods are useful for the production profile interpretation in horizontal wells.
相似文献58.
四会岩体:一个潜在的含钼铜矿化岩体 总被引：1，自引：0，他引：1
四会岩体位于广东省四会市境内,主要由黑云母花岗岩、白云母花岗岩和钾长花岗岩组成。在全岩主、微量元素分析的基础上,对采自该岩体的黑云母花岗岩进行了微区原位LA-ICP-MS锆石微量元素分析和U-Pb定年。CL图像显示这些锆石自形,具有明显的岩浆生长环带,个别有暗色的核。获得了20个有效的206Pb/238U年龄,年龄范围从161~1069Ma。锆石微量元素分析显示这些锆石样品具有高的Th、U和REE含量,明显富集HREE,其Th/U比值普遍高于0.4,表明这些锆石属于岩浆成因。其中年龄最新的一组共10个点比较集中,206Pb/238Pb加权平均年龄为166.6±2.9Ma,代表岩体的成岩时代;其余较老的10个年龄数据比较分散,代表捕获锆石信息。同时这些锆石的Ce(Ⅳ)/Ce(Ⅲ)值为146~681,平均为441,表明形成该岩体的岩浆具有较高的氧逸度;Eu/Eu*值为0.41~0.60,明显高于一般不含矿的岩体(0.4)。将四会岩体锆石Ce(Ⅳ)/Ce(Ⅲ)和Eu/Eu*与邻区粤北大宝山含矿斑岩中锆石(Ce(Ⅳ)/Ce(Ⅲ)=13.9~414;Eu/Eu*=0.14~0.70)进行对比,发现两个参数都比较一致。综合分析表明,四会岩体可能是一个潜在的具有铜钼矿成矿潜力的含矿岩体。 相似文献
59.
铁氧化物-铜-金(IOCG)型矿床:基本特征、研究现状与找矿勘查 总被引：26，自引：3，他引：23
国际上对IOCG型矿床的研究如火如荼,中国则刚刚起步。文章全面评述了IOCG型矿床的研究现状,包括IOCG型矿床的定义、全球时空分布特点、成矿环境、与成矿有关的岩浆岩、矿体形态特征及围岩蚀变、矿床的形成过程、找矿评价标志等。最后,文章从IOCG型矿床的角度,对中国某些矿床进行了思考,认为长江中下游宁芜和庐枞盆地内的玢岩铁矿可能属IOCG型矿床,河北邯邢铁矿和湖北大冶铁矿也有IOCG型矿床的某些特点。 相似文献
60.