魏晋南北朝时期的比丘尼

魏晋南北朝时期，中国历史上第一批比丘尼诞生，当时出家为尼成为由子一种新的归宿。此时的比丘尼在政治、经济上享有许多特权，同时她们作为佛门弟子中的重要群体，对弘扬佛教外采文化、推动佛学的发展做出了突出的贡献。     

房山岩体的岩浆来源、形成机制及动力学意义

房山岩体是华北东部典型的燕山期中酸性侵入杂岩体,其地球化学特征为富Si、Na、Al、Sr,亏损高场强元素(Nb、Ta),轻重稀土分异强烈,Sr-Nd同位素具有类似EMI型富集地幔的特点,表明其岩浆来自于加厚下地壳的部分熔融,并且中生代华北东部下地壳已经被早先的富集岩石圈地幔置换.不同基性程度岩浆的不完全混合是形成微粒闪长质包体的原因.侵入杂岩的角闪石压力计显示下地壳部分熔融形成的中酸性岩浆先后在19~8 km里的深度范围内结晶就位.古太平洋板块在地幔过渡带深度于早白垩世水平俯冲至太行山一线,洋壳脱水导致上覆地幔部分熔融,后者成为加热下地壳部分熔融的热源.     

北魏以来的浑善达克沙地和科尔沁沙地

通过史料考证，提出以下观点：1）北魏时浑善达克、科尔沁两个地区已有沙漠存在，当时称石漠、松漠或大漠；2）辽初至辽末科尔沁沙地沙化程度及分布情况与现代相似；3）元代浑善达克沙地之南北宽度及景观与现代相同；4）20世纪50年代以来沙漠化正过程的主因是草原过度放牧；5）治沙的最佳选项是建设人工草场及围封天然草场，退牧还草．     

Summer sea-surface temperatures and climate events on the North Icelandic shelf through the last 3000 years

Diatom data from core MD992271 on the North Icelandic shelf record a cooling trend through the last 3000 years. This is indicated by a general decrease in warm water species and an increase in cold water taxa. The relative abundance of these two diatom groups changed periodically, suggesting that the climate also fluctuated within this time period. The results of diatom-based transfer function calculation show that the summer sea-surface temperatures (SSTs) before 1400 cal. a BP were generally higher than the mean value for the last 3000 years and the summer SSTs fluctuated around the mean between 1400 and 700 cal. a BP, and dropped to the values below the mean after 700 cal. a BP. Four cooling events were distinguished, centered at around 2600, 1900, 1300 and 600 cal. a BP respectively. The results are not only consistent with the data from neighbouring cores HM107-03 and MD992275, but also comparable with those from the GISP2 ice core and from other marine sediment records in the North Atlantic. This suggests that changes in the summer SSTs reflect regional climate variations in the North Atlantic. On the North Icelandic shelf, the summer SST variation is a result of changes in the in-teraction between the cold and the warm currents in the area.     

终南山与盛唐的隐逸风尚

隐逸文化发展到盛唐即臻于成熟。积极的入世倾向是这一时期隐逸风尚的鲜明特征。临近唐都长安的终南山正是周、汉以来的隐逸圣地。它景色秀美，位置优越，而且分布了大量的佛寺与道观。盛唐的文人士子们便把隐居终南当作进入京城、踏上仕途的最佳途径。他们做出这样的选择，与这一时期昂扬的盛唐气象和唐代皇帝对隐士的特别优渥亦不无关系。     

北秦岭罗汉寺岩群锆石年龄及地质意义

目的准确测定北秦岭罗汉寺岩群辉长岩脉的形成时代,探讨其地质意义。方法采用激光剥蚀等离子质谱法,对辉长岩中锆石进行U-Pb同位素定年。结果辉长岩形成年龄为475 Ma±4 Ma。结论罗汉寺辉长岩脉的形成时代与北秦岭两条高压—超高压变质带和富水杂岩成岩时代接近或一致,它的形成很可能与北秦岭早古生代岛弧体系碰撞有关。     

Chronological record of the Early Mesozoic underplating in the northern margin of North China─U-Pb chronometry of zircons in the Late Mesozoic andesite from Western Liaoning

Cathodoluminescence spectroscopic analysis of zircons in the uppermost sanukites of the early Cretaceous Yixian Formation in Western Liaoning reveals zoning structures of the zircons in the volcanic rocks. LA-ICP-MS chronometry shows that the central part of the zircons is remnant zircon with a U-Pb dating of 254 Ma, which is consistent with the age of the Early Mesozoic underplating granulites, and that the periphery is zircon crystallizing out of the host magma with a U-Pb dating of 116 Ma, which is highly consistent with the Ar-Ar dating of the host volcanic rocks. Compositions of the clinopyroxenes xenocrystals in the sanukites are similar to those of the clinopyroxenes in the underplating granulites, indicating that the granulites accreted to the lower crust in the Early Mesozoic have been reformed and disrupted by the upwelling diapers of the asthenosphere and taken part in formation of the sanukites in the Late Mesozoic.     

Chronological record of the Early Mesozoic underplating in the northern margin of North China—U-Pb chronometry of zircons in the Late Mesozoic andesite from Western Liaoning

Cathodoluminescence spectroscopic analysis of zircons in the uppermost sanukites of the early Cretaceous Yixian Forma- tion in Western Liaoning reveals zoning structures of the zircons in the volcanic rocks. LA-ICP-MS chronometry shows that the central part of the zircons is remnant zircon with a U-Pb dating of 254 Ma,which is consistent with the age of the Early Mesozoic underplating granulites,and that the periphery is zircon crystallizing out of the host magma with a U-Pb dating of 116 Ma,which is highly consistent with the Ar-Ar dating of the host volcanic rocks.Compositions of the clinopyroxenes xenocrystals in the sanukites are similar to those of the clinopyroxenes in the underplating granulites,indicating that the granulites accreted to the lower crust in the Early Mesozoic have been reformed and disrupted by the upwelling diapers of the asthenosphere and taken part in formation of the sanukites in the Late Mesozoic.     

The Dongcaohe ophiolite from the North Qilian Mountains： A fossil oceanic crust of the Paleo-Qilian ocean

The Dongcaohe ophiolite, located at the south of the North Qilian subduction complexes, is a tectonic block with an exposed area of about 3 km×6 km. It consists of an intrusive section overlain by an ex- trusive section. The lower part of the intrusive section consists of cyclic layers of cumulate dunites, troctolites, anorthosites, anorthositic gabbros, and gabbros with small discordant dunite and troctolite bodies. This layered sequence grades upward to isotropic gabbros and gabbronorites, which are overlain by the extrusive sequence of diabasic sheeted dikes and basaltic lavas. The overall mineral crystallization sequence was olivine±Cr-spinel, plagioclase, clinopyroxene, orthopyroxene, and Fe-Ti oxides. The Cr-spinel (Mg#: 42-66, Cr#: 41-57) in these layered cumulates and present-day abyssal peridotites have similar compositions. Also, the compositional variations of the plagioclase and cli- nopyroxene in the intrusive section reflect crystallization from melts compositionally similar to the present-day ocean basalts. Moreover, the rare earth element (REE) and multi-element distribution pat- terns of the intrusive and extrusive lithologies in the Dongcaohe ophiolite are consistent with crystal- lization of mid-ocean ridge basalts. The zircon grains separated from the gabbronorite have an SHRIMP average 206Pb/238U weighted age of 497 ± 7 Ma, which is considered as the tectonic emplacement age of the Dongcaohe ophiolite. The field occurrence, mineral and whole-rock compositions indicate that the Dongcaohe ophiolite represents a well-persevered oceanic crustal fragment composed of a complete oceanic crustal section of layered cumulates at bottom upgrading through isotropic cumulates to sheeted dikes and lava flows.     

Rainfall spectrum change in North China and its possible mechanism

The seasonal distribution of the rainfall in North China has changed greatly since 1977, with more rainfall in spring and less in July, August, and September (JAS). Wavelet analysis showed that the JAS rainfall underwent an abrupt spectrum change in the mid-1960s. Its interannual variability has declined while the interdecadal component has become the dominant mode, associated with the dry climate. Correlation analysis found that the JAS rainfall is negatively correlated with the departures of the 500 hPa geopotential height significantly over the northwest and southwest of China, and positively correlated with the suer monsoon over eastern China. Therefore, the interdecadal ascending of the air pressure in northwestern China and the monsoon decaying over East Asia in the past 20 years may be the two major causes of North China drought.