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11.
12.
西秦岭中生代花岗岩锆石U-Pb-Lu-Hf同位素特征及地质意义 总被引:1,自引:0,他引:1
对西秦岭地区中川岩体、柏家庄岩体和教场坝花岗岩体进行LA-ICP-MS锆石U-Pb同位素年代学分析, 获得其岩浆侵位年龄分别为220±1, 216±6和222±3 Ma, 表明3个岩体均形成于中?晚三叠世。样品的全岩地球化学分析结果表明, 3个岩体具有相似的稀土及微量元素特征, 均表现为显著亏损高场强元素Nb, Ti和P等, 具有明显的右倾式球粒陨石标准化稀土元素配分模式。锆石Lu-Hf同位素分析结果表明, 3个岩体锆石测年样品的εHf(t)值介于?3.31~+1.68之间, 二阶段模式年龄介于1151~1456 Ma之间。岩石成因分析表明, 这些印支期花岗岩体的母岩浆主要来源于新元古代地壳物质的部分熔融。结合岩体形成时代、岩石成因和区域岩浆作用, 认为这些岩体形成于南秦岭与华南板块沿勉略缝合带相碰撞的造山动力学背景, 可能与华南板块的俯冲板片断离有关。 相似文献
13.
ShuangXi Chen TieGang Li Zheng Tang XiaoHua Qiu ZhiFang Xiong QingYun Nan ZhaoKai Xu FengMing Chang 《科学通报(英文版)》2011,56(24):2628-2634
The deglacial δ~13C minimum events that originated from the ventilation of the deep Southern Ocean around Antarctica, have been recorded in a range of marine sediments from the southern to tropical oceans in late Pleistocene. However, the broad δ~13C minimum event was also reported as far as to the northern middle latitudes, in northwestern Pacific marginal sea areas, during the last deglaciation. In the northwestern Pacific, forcing from the northern high latitudes is strongly expressed, while the records of in- fluence from the southern high latitudes are few. The Kuroshio Source Region (KSR) forms a boundary between the northwestern Pacific and the southern, tropical Pacific. So, high-resolution planktonic foraminiferal records in core MD06-3054 from the KSR are well positioned to identify signals from the southern hemisphere in the northwestern Pacific. Planktonic foraminiferal tests from the upper 1030 cm of the core were subject to AMS14C, carbon and oxygen isotopic measurements. A negative excursion was found to occur from about 20.0-6.0 ka BP in δ~13C records of both surface (Globigerinoides ruber) and subsurface (Pulleni- atina obliquiloculata) dwellers, but the overall trends of the two curves have reversed since 26.5 ka BP. Moreover, the δ~13C rec- ord of G. ruber (the surface dweller) shows a robust link to the record of atmospheric CO2, and its changes precede the records of P. obliquiloculata (the subsurface dweller). According to the hydrologic conditions, the broad δ~13C minimum event recorded in the KSR is also a response to the increasing ventilation of the deep Southern Ocean around Antarctica during the last deglaciation. The inconsistency between the records of the surface and subsurface dwellers was possibly caused by the ways that the low δ~13C signal was transmitted. Subsurface water primarily received the low δ~13C signal from the Antarctic Intermediate Water (AAIW), whereas the surface water was probably mainly impacted by atmospheric CO2 in the KSR. The records from the KSR confirm the deduction that the broad δ~13C minimum event in the Okinawa Trough was due to the impact of tropical Pacific surface water dur- ing the last deglaciation, and suggest that signals from the southern high latitudes also can be delivered to the northern middle latitudes. 相似文献
14.
Zircon U-Pb ages of granites at Changba and Huangzhuguan in western Qinling and implications for source nature 总被引:2,自引:0,他引:2
Mesozoic granitoids are widespread in the Qinling-Dabie-Sulu orogenic belt. Precise U-Pb dating on these granitoids can reveal
the evolution of the continental collision orogen and thus provide information on the nature of magma sources. This study
presents zircon LA-ICP-MS U-Pb dating and whole-rock geochemical analyses for two intrusions at Changba and Huangzhuguan in
western Qinling. Zircon U-Pb ages for central and marginal phases of the Huangzhuguang intrusion are 214±1 Ma and 213±3 Ma,
respectively. Zircons from the Changba intrusion yield a dominant cluster with an U-Pb age of 213±2 Ma. Collectively, these
ages are younger than ages of 220 to 240 Ma for ultrahigh-pressure metamorphism due to the continental collision between the
South China Block and the North China Block, corresponding to syn-exhumation magmatism. Some inherited zircons occur in the
Changba intrusion, yielding a weighted mean of 206Pb/238U ages at 757±14 Ma. This indicates that the Changba intrusion has the crustal source of mid-Neoproterozoic ages and a tectonic
affinity to the South China Block. Geochemically, the two intrusuons are both rich in LILE and LREE but depleted in HFSE and
HREE, similar to arc-type igneous rocks. The Huangzhuguang intrusion exhibits linear correlations between SiO2 and the other major oxides, implying chemical evolution from a cognate magma source. It contains mafic enclaves, suggesting
possible mixing of felsic-mafic magmas. The Changba granite is rich in Si and K but poor in Fe and Mg as well as has a high
value of Fe*, suggesting strong differentiation of granitic magma. Therefore, the two intrusions were derived from the Late
Triassic anatexis of the continental crust of different compositions in the northern margin of South China Block. This process
may be coupled with exhumation of the subducted continental crust in the stage of late collision. 相似文献
15.
秦岭地区自然保护区的生态旅游发展对策 总被引:1,自引:0,他引:1
通过分析秦岭地区自然保护区的类型、特点及发展现状,指出秦岭自然保护区在开展生态旅游时应该通过科学规划、严格管理、加强宣传等手段,达到生物多样性保护和经济发展的双赢。 相似文献
16.
《Journal of Natural History》2012,46(9):1047-1103
A total of 101 verified species and eight ordinal taxa represent the non-marine Crustacea on Antarctica and the islands of the Southern Ocean. The largely terrestrial Isopoda and Amphipoda are confined to some sub-Antarctic and cool temperate islands while the predominantly freshwater Anostraca, Anomopoda, Copepoda (=Calanoida, Cyclopoida, Harpacticoida) and Ostracoda (Podocopida) occur throughout the region. Holocene sea-level rises fragmented freshwater and terrestrial species ranges on New Zealand, Auckland, Campbell, and possibly other South Pacific islands, leaving a legacy of vicariant taxa. Tertiary species probably survived Pleistocene glaciation in aquatic refugia on the New Zealand/South Pacific, Falkland, Crozet and Kerguelen archipelagoes, but there are no valid records of Tertiary Antarctic Crustacea. All 40 Continental and Maritime Antarctic freshwater records can be ascribed to the historic introduction of anthropogenic aliens, Holocene immigration of colonists, returning re-colonists and marine species 'marooned' in epishelf and other coastal lakes. 相似文献
17.
《Journal of Natural History》2012,46(8):927-952
There are no terrestrial and freshwater molluscs associated with Continental nor Maritime Antarctica. The malacofaunas of the cool-temperate and sub-Antarctic islands of the Southern Ocean are extremely depauperate, comprising a mere 68 site-records of 51 species from 27 genera in 13 families. The South Atlantic records are confined to the Falkland Islands, which harbour nine species (one bivalve, five pond snails and three terrestrial aliens), and South Georgia, where there is one Notodiscus sp. (Charopidae). The fauna of the South Indian Ocean islands of Prince Edward, Crozet, Kerguelen and Heard, comprises two alien slugs and endemic Notodiscus hookeri (Charopidae). The majority of species occur on the South Pacific Ocean Islands of Macquarie, Campbell, Auckland, Snares, Antipodes, Bounty and Chatham to the south and east of New Zealand. The Chatham fauna is dissimilar to that on the other South Pacific Islands, though both represent vicariant remnants of common South Pacific Is./New Zealand Athoracophoridae, Charopidae and Punctidae. There is, other than the broad South Indian Ocean distribution of Notodiscus hookeri, little evidence of Holocene dispersal and colonization. Indeed the Southern Ocean is an effective barrier and the different regional (South Atlantic/Indian/Pacific) faunas are principally vicariant and derived from local survivors of Pleistocene glaciation. 相似文献
18.
六垛南闸闸下淤积现状分析 总被引:2,自引:0,他引:2
针对我国在滨海河口地区修建的挡潮闸在河口建闸后普遍存在的泥沙淤积问题,根据苏北灌溉总渠入海口六垛南闸等处的实测资料,分析该挡潮闸下潮汐引河通道冲淤特性,指出挡潮闸下引河的潮流特性、潮流挟沙特性及引河淤积的原因。认为对闸门进行科学合理的控制、有效利用上游有限的泄水量和闸下落潮水流拖淤来防淤减淤是较为简便易行且经济的措施。 相似文献
19.
彭金平 《萍乡高等专科学校学报》2009,26(2):115-118
齐初统治者高帝和武帝沿袭了历史上的分封制并有所改进,他们一边重用宗王,一边又对宗王加以严密控制。推行这种宗王制度,既是出于对现实政治环境的考虑,同时也借鉴了历史上对于分封制的经验教训。 相似文献
20.
佘爱春 《玉林师范学院学报》2010,31(1):62-69
《南方文坛》和90年代以来的广西文学是在互动中共同成长、共同发展的。它始终以推介广西文学为己任。通过设置品牌栏目和策划、举办、参与文学活动等形式,为广西文学的持续发展提供理论支持和营造良好的批评氛围,培养和扶持一批青年作家和批评家,对广西文学的崛起和广西文学整体推向全国文坛作出了突出贡献。 相似文献