研究表明,中酸性岩浆岩(包括 SiO_2>56%的中酸性火山岩和侵入岩)的 Sr 和 Yb 是两个非常有意义的地球化学指标,如果大致按照 Sr=400×10^(-6)和 Yb=2×10^(-6)为标志,可以划分出4类花岗岩,即:高 Sr 低 Yb(Sr>400×10^...研究表明,中酸性岩浆岩(包括 SiO_2>56%的中酸性火山岩和侵入岩)的 Sr 和 Yb 是两个非常有意义的地球化学指标,如果大致按照 Sr=400×10^(-6)和 Yb=2×10^(-6)为标志,可以划分出4类花岗岩,即:高 Sr 低 Yb(Sr>400×10^(-6),Yb<2×10^(-6))、低 Sr 低 Yb(Sr<400×10^(-6),Yb<2×10^(-6))、低 Sr 高 Yb(Sr<400×10^(-6),Yb>2×10^(-6))和高 Sr 高 Yb(Sr>400×10^(-6),Yb>2×10^(-6))型花岗岩。其中,从低 Sr 高 Yb 型中还可以分出非常低 Sr 高 Yb(Sr<100×10^(-6),Yb>2×10^(-6))的一类。因此,按照 Sr 和 Yb 含量的不同,可以将花岗岩分为5类,文中着重探讨了这5类花岗岩形成的源区深度问题,指出按照残留相组成和花岗岩地球化学特征,可以将花岗岩形成的压力分为3或4个级别:即:(1)高压下与石榴石平衡的花岗岩具有高 Sr 低Yb 的特征;(2)在中等或较高压力、麻粒岩相(由斜长石+石榴石+角闪石+辉石组成)条件下,花岗岩具低 Sr 低 Yb 或高 Sr 高 Yb 的特点(取决于原岩成分);(3)低压下,残留相有斜长石无石榴石(角闪岩相),花岗岩为低 Sr 高 Yb 类型的;(4)与蛇绿岩有关的在洋壳剖面浅部由辉长岩部分熔融形成的 M 型花岗岩,具有非常低 Sr 高 Yb 的特点,形成深度约2～5km,可能是非常低压条件下形成的。研究表明,淡色花岗岩大多分布在低 Sr 低 Yb 区,部分正长岩和钾玄岩分布在高 Sr 高 Yb 区。藏南淡色花岗岩可能形成的压力较高。文中探讨了岩浆与深度的关系,得出了一些初步的认识,指出需要进一步研究的问题。为了得到经得起考验的结论,还需要更多资料的积累,更多理论的探讨和更多实验的佐证。展开更多
Artemisia ordosica Krasch. is a dominant shrub occurring mainly on stable sand dunes in the Gobi Desert of China, in the Mongolian phytogeographic region. Achenes of A. ordosica germinate in light but poorly in ...Artemisia ordosica Krasch. is a dominant shrub occurring mainly on stable sand dunes in the Gobi Desert of China, in the Mongolian phytogeographic region. Achenes of A. ordosica germinate in light but poorly in dark and light is the limiting factor regulating the achene germination in sand depth. Achenes germinate in spring or autumn with an optimal temperature of 20 ℃. Achene mucilage can absorb large amounts of water and has important ecological function. Salt concentrations and sand moisture may regulate achene germination in sand. A. ordosica, A. sphaerocephala Krasch. and A. monosperma Delile. from different climates have similar responses to light, the underground location of achene, and sand moisture. Percentage of seedling emergence from different levels of sand depth is depends on the specific, temperature and intensity of light penetrating through the sand depths, as well as on sand moisture. The desert sand habitat seems to have had a dominant influence on the evolution of the germination strategies of these 3 Artemisia species.展开更多
Focal depth data of earthquakes in China's Mainland are processed and analyzed in this paper, as well as the relationship between the focal depths and large-scale tectonic structures. As a basic parameter for eart...Focal depth data of earthquakes in China's Mainland are processed and analyzed in this paper, as well as the relationship between the focal depths and large-scale tectonic structures. As a basic parameter for earthquakes, focal depth is used to investigate deep environment of seis-mogenic regions, tectonic backgrounds for concentration and release of seismic energy, the inner crustal deformation and its mechanic features. Depth data of 31282 ML≥2.0 events with 1st class and 2nd class precision in China's Mainland from Jan. 1, 1970 to May 31, 2000 are used to get spatial features of earthquakes distributed with depth and to provide average depth for each grid area throughout China. Researches show that the average depth (D) for all the earthquakes used in this paper is (16±7) km, and (13±6) km and (18±8) km for the events in eastern China and western China, respectively. The area with the deepest focal depth is located in southwest Xinjiang region, near the western and southwestern ends of the Tarim展开更多
文摘研究表明,中酸性岩浆岩(包括 SiO_2>56%的中酸性火山岩和侵入岩)的 Sr 和 Yb 是两个非常有意义的地球化学指标,如果大致按照 Sr=400×10^(-6)和 Yb=2×10^(-6)为标志,可以划分出4类花岗岩,即:高 Sr 低 Yb(Sr>400×10^(-6),Yb<2×10^(-6))、低 Sr 低 Yb(Sr<400×10^(-6),Yb<2×10^(-6))、低 Sr 高 Yb(Sr<400×10^(-6),Yb>2×10^(-6))和高 Sr 高 Yb(Sr>400×10^(-6),Yb>2×10^(-6))型花岗岩。其中,从低 Sr 高 Yb 型中还可以分出非常低 Sr 高 Yb(Sr<100×10^(-6),Yb>2×10^(-6))的一类。因此,按照 Sr 和 Yb 含量的不同,可以将花岗岩分为5类,文中着重探讨了这5类花岗岩形成的源区深度问题,指出按照残留相组成和花岗岩地球化学特征,可以将花岗岩形成的压力分为3或4个级别:即:(1)高压下与石榴石平衡的花岗岩具有高 Sr 低Yb 的特征;(2)在中等或较高压力、麻粒岩相(由斜长石+石榴石+角闪石+辉石组成)条件下,花岗岩具低 Sr 低 Yb 或高 Sr 高 Yb 的特点(取决于原岩成分);(3)低压下,残留相有斜长石无石榴石(角闪岩相),花岗岩为低 Sr 高 Yb 类型的;(4)与蛇绿岩有关的在洋壳剖面浅部由辉长岩部分熔融形成的 M 型花岗岩,具有非常低 Sr 高 Yb 的特点,形成深度约2～5km,可能是非常低压条件下形成的。研究表明,淡色花岗岩大多分布在低 Sr 低 Yb 区,部分正长岩和钾玄岩分布在高 Sr 高 Yb 区。藏南淡色花岗岩可能形成的压力较高。文中探讨了岩浆与深度的关系,得出了一些初步的认识,指出需要进一步研究的问题。为了得到经得起考验的结论,还需要更多资料的积累,更多理论的探讨和更多实验的佐证。
文摘Artemisia ordosica Krasch. is a dominant shrub occurring mainly on stable sand dunes in the Gobi Desert of China, in the Mongolian phytogeographic region. Achenes of A. ordosica germinate in light but poorly in dark and light is the limiting factor regulating the achene germination in sand depth. Achenes germinate in spring or autumn with an optimal temperature of 20 ℃. Achene mucilage can absorb large amounts of water and has important ecological function. Salt concentrations and sand moisture may regulate achene germination in sand. A. ordosica, A. sphaerocephala Krasch. and A. monosperma Delile. from different climates have similar responses to light, the underground location of achene, and sand moisture. Percentage of seedling emergence from different levels of sand depth is depends on the specific, temperature and intensity of light penetrating through the sand depths, as well as on sand moisture. The desert sand habitat seems to have had a dominant influence on the evolution of the germination strategies of these 3 Artemisia species.
基金This work was supported by the National Key Project of Science Technology Development Programme from the Ministry of Science Technology (Grant No. G19980407).
文摘Focal depth data of earthquakes in China's Mainland are processed and analyzed in this paper, as well as the relationship between the focal depths and large-scale tectonic structures. As a basic parameter for earthquakes, focal depth is used to investigate deep environment of seis-mogenic regions, tectonic backgrounds for concentration and release of seismic energy, the inner crustal deformation and its mechanic features. Depth data of 31282 ML≥2.0 events with 1st class and 2nd class precision in China's Mainland from Jan. 1, 1970 to May 31, 2000 are used to get spatial features of earthquakes distributed with depth and to provide average depth for each grid area throughout China. Researches show that the average depth (D) for all the earthquakes used in this paper is (16±7) km, and (13±6) km and (18±8) km for the events in eastern China and western China, respectively. The area with the deepest focal depth is located in southwest Xinjiang region, near the western and southwestern ends of the Tarim
文摘重金属是河道底泥疏浚要控制的重要污染物,而疏浚深度是生态疏浚工程中需要确定的关键参数.本文以杭州经济技术开发区河道为研究对象,共采集18处底泥柱状样,采用土壤背景值、土壤环境质量二级标准值、变异系数和相关性分析方法对底泥中Cu、Zn、Pb、Cd、Ni、As的污染状况进行了评价,同时分析重金属总量和有效态含量在垂向上的变化特征,并引入地累积指数法对各深度底泥中的重金属进行累积性评估,利用本文提出的临界累积深度方法来确定合理的环保疏浚深度.结果表明,河道表层底泥中Cu、Zn、Pb、Cd、Ni、As的平均含量分别为165.16、342.40、55.34、3.61、34.06、36.70 mg·kg-1,Cd、Cu、As、Zn的有效态含量分别为0.007、3.37、0.095、20.76 mg·kg-1,重金属总量均超过了杭嘉湖平原土壤背景值,其中Cd污染最为严重.各重金属元素在底泥中的变异系数为0.29~2.39,空间分布并不均匀.重金属总量和有效态含量随底泥深度的增大整体呈下降趋势,但受不同时期人类活动污染及河道整治影响而呈不规则变化.各重金属元素的富集程度为Cd>As>Zn>Pb>Ni>Cu,其中,Cd污染等级为2~6级,污染程度为中度污染至极强污染.利用临界累积深度方法推算得到研究区域河道底泥环保疏浚深度为0~0.9 m.
