胶莱盆地晚白垩世玄武岩的年代学和地球化学特征及其对华北岩石圈减薄-增生的制约

已有研究认为华北岩石圈减薄的时空不均一是显著的,主要表现在软流圈来源的岩浆最早出现的时间呈现南北差异。本文通过40Ar-39Ar法获得胶莱盆地西官庄拉斑玄武岩的年龄为96±3Ma,属于青山群火山岩的一部分,早于王氏群大西庄碱性玄武岩(73Ma)。两套岩石均缺乏Nb、Ta负异常,分别具有与E-MORB和OIB类似的微量元素配分特征。西官庄拉斑玄武岩((87Sr/86Sr)t=0.7058,εNd(t)=0.37～0.57)和大西庄碱性玄武岩((87Sr/86Sr)t=0.7040,εNd(t)=5.5～5.7)的同位素组成特征均显示软流圈的印记。前者为软流圈熔体与古老富集岩石圈地幔相互反应的产物,而后者是软流圈部分熔融的产物。研究区岩浆的εNd(t)值随年龄的降低而逐渐增大,暗示古老岩石圈减薄过程中软流圈的上涌,说明研究区晚白垩世-早新生代岩石圈仍在经历减薄作用。类似的岩浆演化趋势在辽西和辽东地区也有发现,不过演化的时间分别为120～100Ma和80～60Ma,再次证明华北岩石圈减薄作用的时空不均一性。     

An RXTE observation of the Seyfert 1 galaxy MCG–6-30-15: X-ray reflection and the iron abundance

We report on a 50-ks observation of the bright Seyfert 1 galaxy MCG–6-30-15 with the Rossi X-ray Timing Explorer . The data clearly show the broad fluorescent iron line (equivalent width ∼ 250 eV) and the Compton reflection continuum at higher energies. A comparison of the iron line and the reflection continuum has enabled us to constrain the reflective fraction and the elemental abundances in the accretion disc. Temporal studies provide evidence that spectral variability is a result of changes in both the amount of reflection seen and the properties of the primary X-ray source itself.     

径移主导吸积盘的含时数值模拟

黑洞吸积被认为是活动星系核的能量来源,而研究黑洞吸积最主要的难题是要解释吸积气体的角动量是如何转移出去的.黑洞吸积盘理论提出通过粘滞力矩转移角动量.径移主导吸积盘模型(advection-dominated accretion flow,简称ADAF)是几何厚、光学薄的低吸积率吸积盘模型,它在解释低光度活动星系核的一些观测现象时获得了很大的成功.近年来,随着计算机技术的迅猛发展,数值模拟在天体物理研究中获得了广泛的应用,也取得了突破性的进展.主要工作是用数值模拟方法研究ADAF整体解作为初始条件模拟黑洞的吸积过程.     

The jet power extracted from a magnetized accretion disc

We consider the power of a relativistic jet accelerated by the magnetic field of an accretion disc. It is found that the power extracted from the disc is mainly determined by the field strength and configuration of the field far from the disc. Comparing it with the power extracted from a rotating black hole, we find that the jet power extracted from a disc can dominate over that from the rotating black hole. However, in some cases, the jet power extracted from a rapidly rotating hole can be more important than that from the disc, even if the poloidal field threading the hole is not significantly larger than that threading the inner edge of the disc. The results imply that the radio-loudness of quasars may be governed by its accretion rate, which might be regulated by the central black hole mass. It is proposed that the different disc field generation mechanisms might be tested against observations of radio-loud quasars if their black hole masses are available.     

Carboniferous palaeogeography of the Yarrol and New England Orogens,eastern Australia

During the Carboniferous Period the Yarrol and New England Orogens comprised an active depositional margin east of cratonised parts of Australia. Patterns of deposition within the orogens were probably controlled by dextral shear systems believed responsible for tectonism and the positions of the various depositional elements (volcanic chain, shelf, slope and basin, pull‐apart troughs and graben), and global changes in sea level. These patterns are illustrated by a series of non‐palin‐spastic palaeogeographic reconstructions.

In the Early Carboniferous, similar patterns of deposition existed within the western volcanic chain, marine shelf, and eastern slope and basin provinces of both orogens. Sediments were deposited in two cycles. They range from volcanic fluvial and marine sandstone to siltstone, mudstone and turbidites. Complex depositional patterns within shelfal regions are shown in detailed palaeogeographic reconstructions.

This uniform pattern changed during the latest Visean and Namurian, with the uplift of the New England Arch, subsidence of a non‐marine graben (Werrie Trough) to the west, and development of a new shelf in the east. The Werrie Trough received volcanics as well as fluvial and glacigene sediments, and the shelf marine sandstone and siltstone. The Yarrol Orogen was unaffected by tectonism but there was a change in provenance.

Late in the Carboniferous the Yarrol Orogen was restructured by the intrusion of granitoids into the former volcanic chain, and development of the Yarrol and North D'Aguilar Troughs as probable pull‐apart basins. In the New England Arch, deformation and metamorphism were followed by intrusion of S‐type granitoids. A comparable episode of deformation and metamorphism affected the southeastern part of the Yarrol Orogen at the end of the Carboniferous Period. This partial cratonisation of the mobile zone was a prelude to widespread basin formation during the Permian Period.     

河南渑池县仰韶村遗址不同土层微形态特征研究

仰韶文化时期气候环境与古人类活动是如何变化？大部分变化信息尽管从宏观视野中消失,但却保存在土壤微形态中。故文章采用土壤微形态学方法,对仰韶村遗址一处含有文化层区域进行多点采样,通过比较古土壤、文化层和表土层土壤微形态特点差异,研究了气候变化及古人类活动对土壤微形态的影响,为探究仰韶文化时期的古人类活动遗迹和古农业发展状况提供依据。结果显示：1）古土壤层中具有明确边界的铁质垒结形成物,粗粒质多分解细小颗粒,呈现堆积状,细粒质多为微晶b-垒结,细粒质与粗粒质相对分布主要呈现包膜状和桥接状,孔隙壁附着锰质胶膜。2）文化层中粗粒质多分解细小颗粒,呈现堆积状,细粒质呈现出多种b-垒结,细粒质与粗粒质空间关系也呈现多样化。孔隙壁附着腐殖质,孔道内填充炭屑。3）表土层中土壤形成物主要为继承性钙质形成物和钙质新生体,还可识别淀积黏粒体,土壤垒结回归单一,孔隙呈现出堆集性不规则非稳定态。研究发现：1）古土壤层主要受暖湿气候影响,脱硅富铁铝化作用明显,次生矿物以赤铁矿为主。古人类开始居住活动,促进了土壤发育,淀积黏化作用明显,黏粒胶膜发育充分。2）文化层主要受到古人类活动影响,古人类活动强度增强,土壤形成...     

On the spin paradigm and the radio dichotomy of quasars

We investigate whether models based on the assumption that jets in quasars are powered by rotating black holes can explain the observed radio dichotomy of quasars. We show that in terms of the 'spin paradigm' models, radio-loud quasars could be objects in which the rotation rate of the black hole corresponds to an equilibrium between spin-up by accretion and spin-down by the Blandford–Znajek mechanism. Radio-quiet quasars could be hosting black holes with an average spin much smaller than the equilibrium one. We discuss possible accretion scenarios which can lead to such a bimodal distribution of black hole spins.     

RAT J1953+1859: a dwarf nova discovered through high amplitude QPOs in quiescence

We report the discovery of an accreting binary, RAT J1953+1859, made during the RApid Temporal Survey (RATS) on the Isaac Newton Telescope. It showed high amplitude (0.3 mag) quasi-periodic oscillations on a time-scale of ∼20 min. Further observations made using the Nordic Optical Telescope showed it to be ∼4 mag brighter than in the discovery images. These photometric observations, together with radial velocity data taken using the William Herschel Telescope, point to an orbital period of ∼90 min. These data suggest that RAT J1953+1859 is a dwarf novae of the SU UMa type. What makes RAT J1953+1859 unusual is that it is the first such system to be discovered as a result of high amplitude QPOs during quiescence. This suggests that high-cadence wide-field surveys could be another means to discover cataclysmic variables as a result of their short period variability.     

The long-period AM CVn star SDSS J155252.48+32 0150.9

The Sloan Digital Sky Survey has been instrumental in obtaining a homogeneous sample of the rare AM CVn stars: mass-transferring binary white dwarfs. As part of a campaign of spectroscopic follow-up on candidate AM CVn stars from the Sloan Digital Sky Survey, we have obtained time-resolved spectra of the   g = 20.2  candidate SDSS J155252.48+320150.9 on the Very Large Telescope of the European Southern Observatory. We report an orbital period   P _orb= 3376.3 ± 0.3 s  , or 56.272 ± 0.005 min, based on an observed 'S-wave' in the helium emission lines of the spectra. This confirms the ultracompact nature of the binary. Despite its relative closeness to the orbital period minimum for hydrogen-rich donors, there is no evidence for hydrogen in the spectra. We thus classify SDSS J1552 as a new bona fide AM CVn star, with the second-longest orbital period after V396 Hya  ( P = 65.5 min)  . The continuum of SDSS J1552 is compatible with either a blackbody or helium atmosphere of   T _eff= 12 000–15 000 K  . If this represents the photosphere of the accreting white dwarf, as is expected, it puts the accretor at the upper end of the temperature range predicted by thermal evolution models. This suggests that SDSS J1552 consists of (or formerly consisted of) relatively high-mass components.