江苏沿海地区地形地貌资源的开发与利用

江苏沿海地区地理位置优越,海岸类型以粉砂淤泥质海岸为主,中南部海岸外有辐射状沙洲,形成独特的海岸和海底地形。通过总结江苏沿海地区地形地貌特点,结合以往调查资料的分析研究,对涉及该地区地形地貌资源的开发与利用方面的海洋权益、港口河道及海上工程的建设、扩大陆地面积、地质环境及其开发与利用等方面进行了探讨。     

Deep Fractionation of Clinopyroxene in the East Pacific Rise 13°N:Evidence from High MgO MORB and Melt Inclusions

Mid-ocean ridge basalts(MORBs)from East Pacific Rise(EPR)13°N are analysed for major and trace elements,both of which show a continuous evolving trend.Positive MgO-Al_2O3 and negative MgO-Sc relationships manifest the cotectic crystallization of plagioclase and olivine,which exist with the presence of plagioclase and olivine phenocrysts and the absence of clinopyroxene phenocrysts.However,the fractionation of clinopyroxene is proven by the positive correlation of MgO and CaO.Thus,MORB samples are believe...     

Origin of native sulfur ball from the Kueishantao hydrothermal field offshore northeast Taiwan: Evidence from trace and rare earth element composition

We first report the trace and rare earth element compositions of native sulfur ball with sulfur contents varying from 97.08 wt.% to 99.85 wt.% from the Kueishantao hydrothermal field, off NE Taiwan. We then discuss the sources of trace and rare earth elements incorporated into the native sulfur ball during formation. Comparison of our results with native sulfur from crater lakes and other volcanic areas shows the sulfur content of native sulfur ball from the Kueishantao hydrothermal field is very high, and that the rare earth element (REE) and trace element constituents of the native sulfur balls are very low (∑REE < 35 ppb). In the native sulfur ball, V, Cr, Co, Ni, Nb, Rb, Cs, Ba, Pb, Th, U, Al, Ti and REE are mostly derived from andesite; Mg, K and Mn are mostly derived from seawater; and Fe, Cu, Zn and Ni are partly derived from magma. Based on the sulfur contents, trace and rare earth element compositions, and local environment, we suggest that the growth of the native sulfur ball is significantly slower than that of native sulfur chimneys, which results in the relatively higher contents of trace and rare earth element contents in the native sulfur ball than in the native sulfur chimneys from the Kueishantao hydrothermal field. Finally, we suggest a “glue pudding” growth model for understanding the origin of the native sulfur ball in the Kueishantao hydrothermal field, whereby the native sulfur ball forms from a mixture of oxygenated seawater and acidic, low-temperature hydrothermal fluid with H₂S and SO₂ gases, and is subsequently shaped by tidal and/or bottom currents.     

Talc-beating serpentinized peridotites from the southern Mariana forearc： implications for aseismic character within subduction zones

The serpentinized peridotites overlying the subducted zones in the Izu-Bonin-Mariana (IBM) arc system have been interpret as the cause of the low-velocity layer identified beneath the IBM froearc, in turn few earthquakes occurred along the plate boundary. Chrysotile, which is a low temperature and highly hydrated phase of serpentine with low frictional strength, has been suggested as the low velocity material in the serpentinized peridotites, besides, brucite is inferred to be likely conducive to stable sliding. However, such idea encounters challenging in our serpentinized peridotites from the southern Mariana forearc, which absent both the above minerals. The presence of talc, which characterized by its weak, low-friction and inherently stable sliding behavior, provides new clue. Here we report the occurrence of talc in serpentinized peridotites collected from the landward trench slope of the southern Mariana forearc. We infer that talc is mainly forming as a result of the reaction of serpentine minerals with silica-saturated fluids released from the subducting slab, and talc also occurs as talc veins sometimes. Due to its unique physical properties, talc may therefore play a significant role in aseismic slip in the IBM subduction zone.

     

成都盆地浅层土壤中F来源分析

对成都盆地3061个浅层土壤样品以元素为变量进行F回归分析，在回归模型的基础上进行因子分析，并选取因子载荷较大的元素作为特征元素组合。在结合元素地球化学性质、区域地质背景和因子得分等值线图的基础上，根据特征元素组合来研究F的来源。研究结果表明：①成都盆地浅层土壤中F的来源有6种，其中岷江流经地区出露的酸性岩浆岩、碱性岩和龙门山前陆盆地上三叠统、侏罗系、白垩系沉积岩系是成都盆地浅层土壤中F的主要来源；②F在表生作用过程中显著地发生了迁移，岷江冲积扇成为其富集的“储库”；③自然作用对成都盆地浅层土壤中F的分布特征有显著的影响。     

东太平洋海隆13°N和赤道附近表层沉积物中的元素赋存状态

为了解海底热液活动对沉积物元素赋存状态的影响,对东太平洋海隆(EPR)13°N和赤道附近表层沉积物样品17A-EPR-TVG1、17A-EPR-TVG5做了全样及顺序提取分析,探讨了Al、Ca、Fe、Mn、Ti、Ba、Zn、Cu、Sr、V、Mo、U及稀土元素赋存状态。XRD结果显示,17A-EPR-TVG1沉积物的主要矿物形态为黄铁矿,17A-EPR-TVG5沉积物样品主要矿物为方解石。受热液影响明显的17A-EPR-TVG1沉积物中,除Ca、Sr外,其余元素主要赋存于铁锰氧化物与残留相中。正常深海沉积物17A-EPR-TVG5中,除Al、Ba、Ti外,其余元素主要赋存于碳酸盐相及铁锰氧化物相中。稀土元素的顺序提取结果显示,17A-EPR-TVG1沉积物4个相态稀土元素北美页岩配分曲线中均有Eu正异常,17A-EPR-TVG5沉积物4个相态稀土元素北美页岩配分曲线中均出现Ce负异常,分别指示了二者形成过程中热液与海水的加入。     

Deep Fractionation of Clinopyroxene in the East Pacific Rise 13°N: Evidence from High MgO MORB and Melt Inclusions

Mid-ocean ridge basalts (MORBs) from East Pacific Rise (EPR) 13°N are analysed for major and trace elements, both of which show a continuous evolving trend. Positive MgO–Al2O3 and negative MgO–Sc relationships manifest the cotectic crystallization of plagioclase and olivine, which exist with the presence of plagioclase and olivine phenocrysts and the absence of clinopyroxene phenocrysts. However, the fractionation of clinopyroxene is proven by the positive correlation of MgO and CaO. Thus, MORB samples are believed to show a “clinopyroxene paradox”. The highest magnesium-bearing MORB sample E13-3B (MgO=9.52%) is modelled for isobaric crystallization with COMAGMAT at different pressures. Observed CaO/Al2O3 ratios can be derived from E13-3B only by fractional crystallization at pressure >4 ±1 kbar, which necessitates clinopyroxene crystallization and is not consistent with cotectic crystallization of olivine plus plagioclase in the magma chamber (at pressure ~1 kbar). The initial compositions of the melt inclusions, which could represent potential parental magmas, are reconstructed by correcting for post-entrapment crystallization (PEC). The simulated crystallization of initial melt inclusions also produce observed CaO/Al2O3 ratios only at >4±1 kbar, in which clinopyroxene takes part in crystallization. It is suggested that MORB magmas have experienced clinopyroxene fractionation in the lower crust, in and below the Moho transition zone. The MORB magmas have experienced transition from clinopyroxene+plagioclase+olivine crystallization at >4±1 kbar to mainly olivine+plagioclase crystallization at <1 kbar, which contributes to the explanation of the “clinopyroxene paradox”.     

成都盆地浅层土壤中Cd来源初探

利用四川成都盆地多目标地球化学调查获取的大量数据，通过先线性回归再因子分析等多元统计分析方法，重点研究了浅层土壤Cd元素与其他元素的相关性及在空间上的分布规律，得出浅层土壤中Cd的回归方程及其由元素组合表征的2类来源：自然作用与人为作用。龙门山岩体、沉积地层和硫化物矿床是Cd的主要自然来源；农业活动和城市污染是Cd的人为源，表现为人为作用与自然作用的叠加这为生态评价和污染防治提供了重要参考。