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辽西杨家杖子地区位于华北板块北缘,燕山褶皱带东段。该区侵入岩主要有4种类型:中粗粒钾长花岗岩、斑状钾长花岗岩、似斑状钾长花岗岩和细粒角闪二长岩。其中:主体岩石为中粗粒钾长花岗岩、斑状钾长花岗岩和似斑状钾长花岗岩,均呈较大的岩基出露,沿北东向展布,锆石U-Pb同位素测年结果显示其形成于早侏罗世(181~188 Ma);细粒角闪二长岩多呈岩墙或岩脉产出,近南北向展布,锆石U-Pb同位素测年结果显示其形成于晚三叠世(227 Ma左右)。岩石地球化学分析结果显示:斑状钾长花岗岩和似斑状钾长花岗岩属于弱过铝质高钾钙碱性系列岩石;细粒角闪二长岩属于准铝质高钾钙碱性系列岩石。斑状钾长花岗岩和似斑状钾长花岗岩富集高场强元素Th、La、Nd、Hf和Gd,亏损高场强元素Ti、Ho和大离子亲石元素Ba、Sr;细粒角闪二长岩富集高场强元素Gd、Er和大离子亲石元素Ba、Sr,亏损高场强元素Nb、Hf、Ti、Pr、Y、Yb。稀土配分模式图均为右倾型,轻稀土元素分馏明显,重稀土元素分馏不明显。研究表明该区中生代岩浆作用主要发生在早侏罗世,且与著名的杨家杖子钼矿有着密切的成因联系,而晚三叠世岩浆作用相对较弱。 相似文献
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影响北欧海和楚科奇海夏季细菌丰度和生产力的因素 总被引:3,自引:0,他引:3
Abundance and production of bacterioplankton were measured in the Nordic seas and Chukchi Sea during the5 th Chinese Arctic Research Expedition in summer 2012.The results showed that average bacterial abundances ranged from 3.31×10~(11) cells/m~3 to 2.25× 10~(11)cells/m~3,and average bacterial productions(calculated by carbon)were 0.46 mg/(m~3·d) and 0.54 mg/(m~3·d) in the Nordic seas and Chukchi Sea,respectively.T-test result showed that bacterial abundances were significantly different between the Nordic seas and Chukchi Sea,however,no significant difference was observed regarding bacterial productions.Based on the slope of lg bacterial biomass versus lg bacterial production,bacterial communities in the Nordic seas and Chukchi Sea were moderately dominated by bottom-up control.Both Pearson correlation analysis and multivariable linear regression indicated that temperature had significant positive correlation with bacterial abundance in the Chukchi Sea,while no correlations with productions in both areas.Meanwhile,Chl a had positive correlations with both bacterial abundance and production in these two regions.As the temperature and Chl a keep changing in the future,we suggest that both bacterial abundance and production been hanced in the Chukchi Sea but weaken in the Nordic seas,though the enhancement will not be dramatic as a result of higher pressure of predation and viral lysis. 相似文献
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本文基于生态系统健康的基本逻辑与科学内涵构建评价指标体系,评价2008—2021 年中国沿海11 个省、市和自治区的海洋渔业生态系统健康及各要素层水平,借助传统与空间Kernel 密度估计方法分析中国海洋渔业生态系统健康水平的分布动态演进和长期转移趋势。研究发现:在动态演化特征方面,中国海洋渔业生态系统健康水平随时间的推移提升效果显著,其内部各地区海洋渔业生态健康水平的绝对差异呈上升趋势,且极化现象存在加剧趋势。从各要素层分布曲线来看,海洋渔业生态系统活力的下滑制约了海洋渔业生态系统健康水平的提升;海洋渔业生态系统弹性的变化拉动了海洋渔业生态系统健康水平的不断攀升。在长期转移趋势方面,不考虑空间因素条件下,沿海各地区海洋渔业生态系统健康水平具有较强的稳定性与连续性,在3 年的时间跨度内实现跨越式等级跃迁的可能性较小,且存在向低水平和高水平“俱乐部收敛”的可能性。考虑空间因素条件下,中国海洋渔业生态系统健康水平在空间动态条件下的演进趋势呈现“断层”现象。处于1.2耀1.4 临界级与良好级的相邻地区间存在趋同性,而处于0.6 以下风险级与1.4 以上良好级的地区不易与相邻地区发生空间关联作用。 相似文献
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