滇西昌宁阿愿山花岗岩锆石U-Pb年代学特征及其地质意义

采用LA-MC-ICPMS锆石U-Pb测年方法,确定了阿愿山花岗岩体的形成时代。研究表明,阿愿山花岗岩体锆石U-Pb年龄为(238±1)Ma。岩体所具有的岩相分带和冷凝边,表明岩体与围岩间为侵入接触关系。由岩体的侵位年龄、围岩的岩石组合共同限定有时代有争议的围岩可能属于无量山岩群。     

天堂山水库坝区断裂构造基本特征及其活动性

野外调查与室内分析表明,影响大坝基础稳定性的北西向断裂属不活动断层;压碎岩占80％以上,强度较高,有利于坝基工程基础处理;引水隧道及峒室工程必需考虑现今构造应力场主压应力近南北向来布置,以减少构造应力对围岩稳定性带来的不利影响。     

Peat record reflecting Holocene climatic change in the Zoige Plateau and AMS radiocarbon dating

Through the use of reliable AMS dating of high resolution (15-30 years) peat and the establishment of monsoon climate proxies sequence, we have been able to recognize several cold, dry events in the Tibetan Plateau during the Holocene. The more obvious ones occurred around 12800, 11300, 10200, 9580, 8900, 6400, 4400, 3700, 2800 and 1500 cal. aBP. These events correlate well with both ice rafting events recorded in high latitude North Atlantic Ocean sediment cores and cooling events in the low latitude SST. Spectral analysis indicates high frequency climate variation on centennial-millennial time scale during the Holocene. This further reflects Holocene climate instability and the existence of centennial-millenium scale rhythm in mid latitude areas as well.     

Re-Os dating of gold-bearing arsenopyrite of the Maoling gold deposit,Liaoning Province,Northeast China and its geological significance

The Maoling gold deposit, one of the large gold deposits in eastern Liaoning Province, NE China, is an arsenopyrite-disseminated gold deposit with a resource of approximately 25 t Au and an average Au grade of 3.2 g/t. Six arsenopyrites closely related to Au mineralization of the Maoling gold deposit are dated by Re-Os technique and define a Re-Os isochron with an age of 2316±140 Ma, which suggests that the deposit was formed in the Paleoproterozoic era rather than in the Indosinian period as some early researchers suggested. High initial ^187Os/^188Os ratio of 1.32±0.48 indicates a crustal derivation of the ore-forming material of the deposit, which may be derived from rocks of the Gaixian formation of the Liaohe Group. Furthermore,the result also implies that the age of the Gaixian Formation in the Maoling district is older than 2316±140 Ma.     

Ultra-low procedural blank and the single-grain mica Rb-Sr isochron dating

Both low procedural blank and high-precision measurements of isotopic ratios are crucial for the analysis of micro samples. This study reports a chemical procedure of ultra-low blank for the high precision measurement of Sr isotopic ratios on micro samples （〈1 ng level） using a new-type thermal ionization mass spectrometer IsoProbe-T, with a case study of single-grain Rb-Sr isochron dating on phlogopite from the Fuxian kimberlite in Liaoning Province. This method can be employed in studies of high resolution Rb-Sr geochronology and Sr isotopic geochemistry and thus will broaden application of the Rb-Sr isotopic system to earth sciences.     

Identification of Hercynian shoshonitic intrusive rocks in central Hainan Island and its geotectonic implications

Hercynian (Variscan) orogenic belts, including the European-NW African orogen, the Appalachian orogen of North America and the central Asia-Mongolia- Hinggan orogen, etc., are widely distributed in the world. Their extensions are often several thousand ki…     

Identification of 3.5 Ga detrital zircons from Yangtze craton in south China and the implication for Archean crust evolution

The LA-ICP-MS U-Pb dating of hundreds of detrital zircon grains from the Sinian sandstones of Liantuo formation and tillites of Nantuo formation at Sanxia area in Yichang identified 3319?3508 Ma zircon grains. Their ²⁰⁷Pb/²⁰⁶Pb and ²⁰⁶Pb/²³⁸U ages show excellent agreement (concordia degree 99%?100%). Their CL images exhibit well-developed oscillatory zoning and the Th/U ratios are within 0.46?0.76, implying that they are igneous zircons which formed during middle-early Archean. These zircons are the oldest ones discovered in Yangtze craton until now. However, the detrital zircons with ages older than 3.3 Ga in the metamorphic rocks of Kongling group were not found by further investigation, which suggests the presence of crust older than high-grade metamorphic Kongling terrain in Yangtze craton.     

米兰柯维奇地质定年方法的数学表达及其意义

重点讨论了米兰柯维奇理论地质定年若干问题的数学表达及其意义。结果表明：利用米兰柯维奇理论进行地质定年的理论依据是充分的；加强对沉积速率及其分布特征的统计和研究是改进米兰柯雏奇理论地质定年效果的重要途径之一，另一重要途径则是提高被处理层段地质持续时间的确定精度；被处理井段所对应的地质持续时间，应不小于米兰柯维奇理论地质定年方法的分辨率；当被处理井段厚度较大时，应当注意米兰柯维奇旋回对应频率成分的能量大小，是否能保证旋回识别的有效性。该方法是一种新的定年方法，其数学表达式易于计算机运算的实现，为自动化定年提供了可能。     

北京王府井东方广场古人类遗迹热释光断代

东方广场位于北京王府井地区。施工开挖中发现,在埋深大约10.5m和12m处分别有2层河流砂层,含化石、石器、灰烬等物。经热释光断代方法测定,上层约为距今1.5至1.9万年,下层约为距今2.2至2.6万年。