西藏过铝花岗岩的岩石化学特征及成因探讨   总被引：7，自引：1，他引：6  

廖忠礼  莫宣学  潘桂棠  朱弟成  王立全  耿全如  赵志丹  熊兴国  董国臣 《地质学报》2006,80(9):1329-1341

西藏班公湖—改则—安多—怒江带一线以南分布有61个主要过铝花岗岩体,其岩石类型主要有电气石花岗岩、白云母花岗岩和二云母花岗岩,它们的主量元素组成为SiO2=65.70%~79.52%、K2O Na2O=2.20%~12.51%、K2O/Na2O=0.49~1.04及A/CNK=1.04~1.38。随着SiO2的增加,岩石中Al2O3逐渐下降,而其他的氧化物较离散。岩石系列主要为含钾较高的钙碱性系列,具典型的(强)过铝花岗岩特征。铝饱和指数图解、QAP图解投点大多数落在CCG区,表明其为大陆碰撞构造环境。Ab-Or-Q-H2O相图表明过铝花岗岩形成的压力为0.05~0.2GPa,推断温度低于700℃。根据岩石化学分析,可以得出这样的推论,西藏过铝花岗岩类发生在两个大陆地壳板块的碰撞阶段,源岩来源于上地壳的重熔,成因为S型花岗岩。其中南冈底斯带和拉轨岗日带具有许多相似的性质,这些相似的性质可能暗示二者有相同的岩浆源区或(和)相同的构造环境。  相似文献   

A multivariate assessment of the coral ecosystem health of two embayments on the lee of the island of Hawai'i     

Parsons ML  Walsh WJ  Settlemier CJ  White DJ  Ballauer JM  Ayotte PM  Osada KM  Carman B 《Marine pollution bulletin》2008,56(6):1138-1149

Four coral-dominated coastal sites within two embayments (Kealakekua Bay and Honokōhau Bay) on the lee of the island of Hawai'i were studied to assess evidence of anthropogenic impacts in these relatively pristine locales. Nutrient-loading parameters were analyzed in relation to benthic composition data. Statistically, there were significant positive relationships between nitrate+nitrite, silicate, and ammonium with the abundance of macroalgae, coralline algae, and dead coral, and between delta(15)N and dead coral abundance. The north outside site of Kealakekua Bay and the south outside site of Honokōhau Bay appear to be most impacted by nutrient-loading factors in each bay, respectively. Comparisons with past nutrient data indicate that nutrient inputs have increased to the two bays, and that early impacts of these increased loadings are evident. It is predicted that at current nutrient-loading rates, the north sites of Kealakekua Bay and the south sites of Honokōhau Bay will exhibit evidence of further degradation in future years.  相似文献   

Empirical models to identify mechanisms driving reductions in tissue mercury concentration during culture of farmed southern bluefin tuna Thunnus maccoyii     

Balshaw S  Edwards JW  Ross KE  Ellis D  Padula DJ  Daughtry BJ 《Marine pollution bulletin》2008,56(12):2009-2017

Two empirical models are presented to elucidate the mechanisms driving reductions in the mercury concentration of southern bluefin tuna (SBT) during culture. Model 1 predicts temporal fluctuations in mercury concentration in response to growth dilution. Model 2 predicts the combined effects of growth dilution and linear mercury accumulation. Model 2 was found to be the more accurate model. Over a typical farming period of 136 days, growth dilution resulted in a reduction in mean mercury concentration of SBT edible tissues from 0.51 mg/kg down to 0.33 mg/kg. Extended culture beyond 136 days resulted in an increase in mercury concentration due to the combined effects of mercury accumulation and seasonal lipid depletion. Results indicate that under current industry practice, cultured SBT can be consumed twice as frequently as that of wild caught SBT while maintaining total dietary mercury intake below national recommendations.  相似文献   

华南南盘江盆地早三叠世钙质微生物丘与生物层   总被引：1，自引：0，他引：1  

Lehr.  DJ 康云骥 《广西地质》2000,13(2):75-78

在南盘江盆地海相弧立的碳酸盐台地内部发现早三叠世生物骨架灰岩。它们发育于２个层位：１．三叠系最底部哥里斯巴赫阶（Ｇｒｉｅｓｂａｃｈｉａｎ）,为１５ｍ厚的生物层;２．下三叠统上部史密斯阶－－斯帕斯阶（Ｓｍｉｔｈｉａｎ－－Ｓｐａｔｈｉａｎ）,为１．５ｍ厚弧立的穹隆形或倒置的贺锥形钙质微生物丘。这些钙质微生物丘与生物层是由坚硬的钙质策生物骨架组成,这些骨架围限出１￣３ｃｍ大小的内部孔洞网,期间充以团粒和  相似文献   

使用改进型破裂时间法对南加州做中期地震预测     

Brehm  DJ 杨国栋 《世界地震译丛》1999,(6):16-35

根据由南加州地震目录回顾性地震建模及已发表的对新马德里震带的估算结果,改进型破裂时间法可以作为一种中期地震预测技术用来确定未来主震的地点并预测其大小和时间。提出假设并对先前主震的建模表明本方法预测的离震震级精度达到了约±０．５个震级单位。假设已有兆序列中最后的事件,则破裂时间误差约是±１．１年。当不知识序列中最后的事件时,预测震级保持桢,但随着时间的推移,往序列中追加事件时,预测时间将需要更新。本  相似文献   

Patterns of inorganic phosphate uptake in Cassiopea xamachana: a bioindicator species     

Todd BD  Thornhill DJ  Fitt WK 《Marine pollution bulletin》2006,52(5):515-521

Nutrient levels in the nearshore waters of the Florida Keys have increased over the past few decades concomitant with a decline in the health of Florida's reef system. Phosphorus is a particular concern in the Florida Keys as it may be the limiting nutrient in nearshore waters. We demonstrate that the upside-down jellyfish, Cassiopea xamachana, decreases its rate of phosphate uptake following exposure to elevated levels of dissolved inorganic phosphate. We also show that this subsequent suppression of uptake rates persists for some time following exposure to elevated phosphates. Using these attributes, we experimentally investigated the use of C. xamachana as a bioindicator for dissolved inorganic phosphates in seawater. Our results show that these animals reveal comparative differences in environmental phosphates despite traditional testing methods yielding no detectable phosphates. We propose that C. xamachana is a bioindicator useful for integrating relevant information about phosphate availability in low nutrient environments.  相似文献   

赣西小龙金矿热液活动与成矿作用特征     

杨斌  董国臣  曾书明  孔会磊  刘金元  宋云涛  王伟清 《矿床地质》2011,30(1):125-138

赣西小龙金矿区位于萍乐凹陷带中部竹亭-涧溪深大断裂带附近,矿区内的Au矿化明显受近EW向断裂的控制,与构造活动导致的热液渗透相关.文章在岩相学和地球化学研究的基础上,认为围岩蚀变的特点是以强硅化为主导,伴有轻微的去碳酸盐化和泥化;围岩蚀变是同阶段多期次热液作用的结果,并无明显的分带现象.通过常量元素地球化学特征解析以及...  相似文献   

基于GIS的证据权重法对三江地区的铜矿成矿预测   总被引：1，自引：0，他引：1       下载免费PDF全文

李荣  董国臣  王硕  孔会磊  聂飞 《沉积与特提斯地质》2011,(3):100-106

根据研究区铜矿的成矿规律,在已经建立的三江地质矿产数据库的基础上,将三江地区划分为6418个统计单元,利用GIS的空间分析功能提取了地层、岩体、断裂在内的12个证据图层,建立了证据权找矿模型,圈定出44个找矿远景区,其中A类远景区9个,B类远景区15个,C类远景区20个,并预测了找矿潜力。  相似文献   

关于“洋脊俯冲作用运动学及其对地幔上涌作用性质指示意义”的讨论     

Thor.  DJ 张春福 《地质科学译丛》1995,12(3):21-23

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瑞士阿尔卑斯山金矿化的新类型：迪森蒂斯金矿化     

Knopf  DJ 《地质地球化学》1991,(2):7-11,38

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