白垩纪温度较冷的估价

白垩纪温度较冷的估价Ｂ．ｗ．Ｓｅｌｌｗｏｏｄ等有关白垩纪气候的概念部分基于详尽的地质证据，如不耐寒冷的古生物（如：珊瑚的分布比现在偏极地５－１５℃）和特殊气候条件的沉积相的广泛分布。这些资料的解释反映２１℃的等温线在纬度上至少向两极移动５°，全球的平...     

Origin of the hydrocarbon component of carbonaceous chondrites: the star-meteorite connection

We report the results of an experiment that produced a residue which closely matches the hydrocarbon component of the Murchison carbonaceous chondrite. This experiment suggests that the parent material of the meteoritic component originated as polycyclic aromatic hydrocarbon species in carbon stars during their later stages of evolution. The experiments also indicate that the pathway from those formation sites to eventual incorporation into the meteorite parent body involved hydrogenation in a plasma in the solar nebula or in H II regions prior to the solar nebula. This model is consistent with what is known about the meteoritic hydrocarbon component including deuterium abundance, the observation of cosmic infrared emission bands best attributed to polycyclic aromatic hydrocarbon molecules, and the inherent stability of these molecules that allows their formation in stars and subsequent survival in the interstellar medium.     

丘陵草坡土壤10Be分布特征及土壤生成速率

以位于广东省境内的中国科学院鹤山丘陵综合试验站草坡集水区土壤剖面为对象, 对土壤样品进行了大气成因¹⁰Be测定, 对基岩以及风化岩石样品进行了就地(in-situ)宇宙成因¹⁰Be测定. 基于土壤层大气成因¹⁰Be测定, 参考土壤层底界¹⁴C表观年龄, 估算出草坡地区3800年以来大约有34%的成土物质被侵蚀掉; 基于风化岩石间隙土大气成因¹⁰Be测定, 估算得到基岩之上90 cm厚的风化岩石层至少经历了1.36 Ma, 平均侵蚀速率约为1.26×10^-4 cm/a. 表面风化岩石和基岩就地成因¹⁰Be浓度分别为10.7×10⁴ atoms/g和 8.31×10⁴ atoms/g, 据此估算得到: 土壤生成速率为8.8×10^-4 cm/a; 表层风化岩石以及基岩宇宙射线暴露时间分别约为7.2×10⁴和2.3×10⁵a. 土壤生成速率大于侵蚀速率, 自然地貌状况稳定.     

斐济一汤加地幔过渡带的地震波各向异性

论述了一个不常见的、明显的过渡带(TZ)各向异性的实例，证据来自于许多比垂直偏振剪切波(SV)早到3S的水平偏振剪切波(SH)。各向异性区与远离活动俯冲带及已知的纵、横波速度横向非均匀体边界的深震相关。我们把这一各向异性区解释为与岩石层残骸中的巨大岩石异常体有关的强组构，这个巨大的岩石异常体悬浮并滞留于过渡带中。冷板块的快速俯冲非常适合于这种组构的形成，因此板块穿透到下地幔并不能普遍发生。     

利用地理挖掘概念推动地理知识获取的可行性研究:第一篇

总结了近阶段一系列的多媒体用于检索各种为空间信息提供图形接口的方式。在20世纪 80年代这种方法导致产生了交互式的原型激光碟,用于评价媒体在信息发布上的有效性,随后提出并发展了地理挖掘概念。地理挖掘概念是     

The Preliminary Statistical Analysis of LAMOST DR8 Low Resolution AFGK Stars

We download the Large sky Area Multi-Object fiber Spectroscopic Telescope Data Release 8(LAMOST DR8)low resolution catalog for 6,478,063 AFGK type stars and plot the figures of effective temperature,gravitational acceleration and metal abundance.Some small and medium mass stars are evolved from pre-main sequence or main sequence stage to planetary nebula stage or white dwarf stage by the stellar evolution code MESA.We analyze the observed statistical data and model calculation results,and then o...     

Structural and tectonothermal evolution of the ultrahigh-temperature Bakhuis Granulite Belt,Guiana Shield,Surinam:Palaeoproterozoic to recent

We constrain the multistage tectonic evolution of the Palaeoproterozoic UHT metamorphic(P=0.9–1.0 GPa,T>1000℃,t=2088–2031 Ma)Bakhuis Granulite Belt(BGB)in Surinam on the Guiana Shield,using large-to small-scale structures,Al-in-hornblende thermobarometry and published fluid inclusion and zircon geochronological data.The BGB forms a narrow,NE–SW striking belt between two formerly connected,~E–W oriented granite-greenstone belts,formed between converging Amazonian and West African continental masses prior to collision and Transamazonian orogeny.Inherited detrital zircon in BGB metasediments conforms agewise to Birimian zircon of West Africa and suggests derivation from the subsequently subducted African passive margin.Ultrahigh-temperature metamorphism may have followed slab break-off and asthenospheric heat advection.Peak metamorphic structures result from layer-parallel shearing and folding,reflecting initial transtensional exhumation of the subducted African margin after slab break-off.A second HT event involves intrusion,at ca.0.49 GPa,of charnockites and metagabbros at 1993–1984 Ma and a layered anorthosite at 1980 Ma,after the BGB had already cooled to<400℃.The event is related to northward subduction under the greenstone belts,along a new active margin to their south.A pronounced syntaxial bend in the new margin points northward towards the BGB and is likely the result of indentation by an anticlinorial flexural bulge of the subducting plate.Tearing of the subducting oceanic plate along this bulge explains why the charnockites are restricted to the BGB.The BGB subsequently experienced doming under an extensional detachment exposed in its southwestern border zone.Exhumation was focused in the BGB as a result of the flexural bulge in the subducting plate and localised heating of the overriding plate by charnockite magmatism.The present,straight NE–SW long-side boundaries of the BGB are superimposed mylonite zones,overprinted by pseudotachylites,previously dated at ca.1200 Ma and 950 Ma,respectively.The 1200 Ma mylonites reflect transpressional popping-up of the BGB,caused by EW-directed intraplate principal compressive stresses from Grenvillian collision preserved under the eastern Andes.Further exhumation of the BGB involved the 950 Ma pseudotachylite decorated faulting,and Phanerozoic faulting along reactivated Meso-and Neoproterozoic lineaments.     

在世界包围中的新西兰农业:当今政策的调整

在这篇文章里,我研究了十九世纪世界贸易和殖民扩展中的新西兰农业发展,继而研究了导致农业出口依赖于世界贸易、技术和动力平衡所出现的经济过程。我调查了农业(1963—1984年)近期的竞争,以及转向调整和出现二十世纪经济和剩余农业的含意。     

澳大利亚前寒武系和寒武系迭层石的分布

前言我们在澳大利亚工作的目的是检验苏联迭层石分类及其分带方案(Scheme)的可靠性。我们发现他们的分类,如在别处讨论过的一样,在我们的迭层石中一般是可应用的。我们尽可能广泛地获得了迭层石在地理和时代(temporal)上分布范围的资料。普里斯(1971)对阿得累德(Adelaide)地槽前寒武纪和寒武纪迭层石作了详细的地层和岩相研究。沃尔特(1970,1972)研究了阿马德斯(Amadeus)、乔治纳(Georgina)、麦卡阿瑟