西藏波密花岗岩体的年代学、地球化学特征及其意义   总被引：1，自引：1，他引：0  

李炜恺  谢锦程  董国臣  莫宣学  赵志丹  王天赐 《岩石学报》2013,29(11):3745-3754

波密岩体位于西藏东南部,处于班公湖-怒江蛇绿混杂岩带与印度河-雅鲁藏布蛇绿混杂岩带之间,整体呈NW向延伸,面积约29km²。本文对波密花岗岩体进行了系统的岩石学、地球化学及同位素年代学研究。结果显示,波密岩体主要以黑云母石英闪长岩与黑云母花岗闪长岩为主,两个花岗闪长岩的LA-ICP-MS锆石U-Pb年龄分别为113.1±2.3Ma和113.4±2.1Ma。花岗岩类SiO₂介于64.11%~66.63%,K₂O+Na₂O=6.36%~7.54%,全碱含量较高,属于高钾钙碱系列。稀土元素含量为114.9×10^-6~182.8×10^-6,分配曲线均呈右倾趋势。另外,A/CNK为0.80~0.95,波密岩体有高K,高Si,低P的特点,大离子亲石元素(Rb、K)富集,高场强元素(Nb、Ta、P、Ti)亏损,属于偏铝质I型花岗岩。2件样品37个测点的锆石ε_Hf(t)值不均一,几乎全为负值(-13.72~-0.08),反映岩浆可能源于古老地壳;地壳模式年龄(t_DM^C)集中于891~2047Ma之间。综合分析波密岩体地球化学及锆石年龄数据,均与中冈底斯及弧背断隆带中早白垩世的岩体特征相似。因此本文推断波密岩体的成因为中冈底斯早白垩世带状岩浆大爆发事件在东部的延续。  相似文献   

中国东北地区自然重砂及其矿物组合对金矿类型的响应     

韦少港  董国臣  王松洋  董美玲  贾丽琼  聂飞  张翔  薄海军 《地质论评》2013,59(Z1):371-372

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拉萨地体的起源和古生代构造演化   总被引：19，自引：0，他引：19  

朱弟成  赵志丹  牛耀龄  王青  Yildirim DILEK  董国臣  莫宣学 《高校地质学报》2012,18(1):1-15

早期由于资料有限,对拉萨地体古生代时期的裂解、漂移、俯冲和碰撞历史的认知程度还很低。本文利用目前已有
地质和地球化学资料,分析了拉萨地体的中生代岩石圈结构,探讨了拉萨地体的起源和古生代演化历史。大量长英质岩石
的锆石Hf 同位素和全岩Nd 同位素表明,南部和北部拉萨地体以新生地壳为主,部分地区可能存在前寒武纪结晶基底,而
中部拉萨地体是具有古元古代甚至太古代结晶基底的条带状微陆块。大量古生代沉积岩的碎屑锆石U-Pb 年龄数据表明,拉
萨地体约1170 Ma 的碎屑锆石年龄指标,明显不同于以约950 Ma 为碎屑锆石年龄指标的安多、羌塘和特提斯喜马拉雅。拉
萨地体起源于澳大利亚大陆北缘是目前资料情况下的最合理解释。中部拉萨地体约492 Ma 的双峰式火山岩形成于活动大陆
边缘背景,代表了古地理上位于澳大利亚大陆北缘的岩浆弧的一部分,可能与原特提斯洋岩石圈板片的断离有关。拉萨地
体南缘和南羌塘的泥盆纪末期-石炭纪早期片麻状花岗岩类为存在明显幔源物质输入的S 型花岗岩,可能形成于最终演化
为松多特提斯洋的弧后盆地背景。中二叠世末期发生的拉萨地体与澳大利亚大陆北缘的碰撞造山事件可能触发了班公湖-
怒江特提斯洋岩石圈的南向俯冲,并随后对拉萨地体的中生代构造岩浆演化发挥关键性作用。  相似文献   

滇西三江地区临沧花岗岩的岩石成因:地球化学、锆石U-Pb年代学及Hf同位素约束   总被引：21，自引：12，他引：9  

孔会磊  董国臣  莫宣学  赵志丹  朱弟成  王硕  李荣  王乔林 《岩石学报》2012,28(5):1438-1452

位于滇西三江地区南澜沧江带的临沧花岗岩,其岩石类型主要为黑云母二长花岗岩,研究结果表明,该花岗岩的SiO2含量为66.84%～73.99%,平均为69.72%,K2O/Na2O值高,为1.42～30.1,平均为8.66,Al2O3含量为12.94%～15.23%,平均为14.44%,铝饱和指数A/CNK为1.06～8.59,平均为2.61,大部分大于1.1,为高钾钙碱性过铝-强过铝花岗岩。岩石总体上富集大离子亲石元素和Pb,明显亏损高场强元素。稀土总量198.2×10-6～359.2×10-6,平均为252.5×10-6,具有明显的轻稀土富集,重稀土亏损的特征,(La/Yb)N为7.87～17.62,平均11.19,δEu为0.34～0.57,平均0.48,球粒陨石标准化配分模式显示明显的负Eu异常。两件样品的锆石U-Pb年龄分别为219.19±0.99Ma和219.69±0.67Ma,属晚三叠世。SiO2-P2O5、SiO2-Zr判别图、K2O-Na2O判别图、ACF图解等花岗岩成因类型判别图指示临沧花岗岩为S型花岗岩,其物质来源为贫粘土的砂屑岩。微量元素Rb-Y+Nd判别图中,临沧花岗岩体投影点全部落入后碰撞花岗岩区。在Sr-Yb判别图中,投影点大部分落入低Sr高Yb型花岗岩区,与我国东南沿海花岗岩特征一致,应形成于挤压向伸展转换的后碰撞阶段。锆石Hf同位素组成比较均一,εHf(t)均为负值(集中于-14～-11之间),Hf地壳模式年龄集中于1.95～2.15Ga,推断其为古老地壳部分熔融的产物。结合锆石定年结果及岩体产出的区域地质背景,我们认为临沧花岗岩形成于缅泰马陆块与思茅地块大陆碰撞造山过程的后碰撞阶段,应形成于晚三叠世。  相似文献   

Lithium isotope geochemistry and origin of Canadian shield brines   总被引：3，自引：0，他引：3  

Bottomley DJ  Chan LH  Katz A  Starinsky A  Clark ID 《Ground water》2003,41(6):847-856

Hypersaline calcium/chloride shield brines are ubiquitous in Canada and areas of northern Europe. The major questions relating to these fluids are the origin of the solutes and the concentration mechanism that led to their extreme salinity. Many chemical and isotopic tracers are used to solve these questions. For example, lithium isotope systematics have been used recently to support a marine origin for the Yellowknife shield brine (Northwest Territories). While having important chemical similarities to the Yellowknife brine, shield brines from the Sudbury/Elliot Lake (Ontario) and Thompson/Snow Lake (Manitoba) regions, which are the focus of this study, exhibit contrasting lithium behavior. Brine from the Sudbury Victor mine has lithium concentrations that closely follow the sea water lithium-bromine concentration trajectory, as well as delta6Li values of approximately -28/1000. This indicates that the lithium in this brine is predominantly marine in origin with a relatively minor component of crustal lithium leached from the host rocks. In contrast, the Thompson/Snow Lake brine has anomalously low lithium concentrations, indicating that it has largely been removed from solution by alteration minerals. Furthermore, brine and nonbrine mine waters at the Thompson mine have large delta6Li variations of approximately 30/1000, which primarily reflects mixing between deep brine with delta6Li of -35 +/- 2/1000 and near surface mine water that has derived higher delta6Li values through interactions with their host rocks. The contrary behavior of lithium in these two brines shows that, in systems where it has behaved conservatively, lithium isotopes can distinguish brines derived from marine sources.  相似文献   

Funding in integrated coastal zone management partnerships     

McGlashan DJ 《Marine pollution bulletin》2003,46(4):393-396

In countries where integrated coastal zone management (ICZM) is not enshrined in statute, a voluntary approach has often been taken. This review examines issues relating to funding in ICZM partnerships, particularly the local coastal fora (LCF) network in the UK. It highlights the lack of sustainable long-term funding mechanisms for organisations with the core aim of sustainable management of coastal resources. The relative difficulty of raising funds for core costs as opposed to projects is addressed, as is the lack of business/industry involvement. The 'hamster wheel syndrome' of fundraising is noted, where staff spend too much time trying to raise money, as opposed to developing ICZM. The resultant impact on the staff and the operation of the LCF is considered. Examples beyond the UK are considered, as are the problems associated with 'pump-prime' funding and implementation. Is the lack of formality in ICZM the crux of the funding problem?  相似文献   

Imposex in the indigenous Nassarius kraussianus (Mollusca: Neogastropoda) from South African harbours     

Marshall DJ  Rajkumar A 《Marine pollution bulletin》2003,46(9):1150-1155

Nassarius kraussianus populations in the Durban and Richards Bay harbours (along the eastern seaboard of southern Africa) and in the Knysna lagoon (southern Cape coast) showed imposex development, confirming bioavailability of tributyltin (TBT) in these waterways. Incidence of imposex (which ranged from 29% to 100%) and relative penis length of females (RPL; which ranged from 1.3% to 55.2%) were markedly variable among populations from different sites in each waterway, indicative of localised effects of TBT contamination. Shell length of the snails was apparently not correlated with contamination level, as assessed from imposex measurements. While population imposex features are easy to determine and often provide a sensitive biomarker of TBT exposure, the discussion outlines reservations when extrapolating these to general ecological situations. Additionally, this study represents the first published report on the topic for sub-Saharan, African harbours, some of which seem remarkably less affected than suggested for other world regions.  相似文献   

Organochlorine compounds and aliphatic hydrocarbons in Pacific walrus blubber     

Seagars DJ  Garlich-Miller J 《Marine pollution bulletin》2001,43(1-6):122-131

Blubber samples were collected from 8 male and 19 female Pacific walrus (Odobenus rosmarus divergens) taken during a 1991 joint USA/USSR cruise traveling widely through the Bering Sea. Dieldrin was found at a level similar to that reported 10 years earlier; oxychlordane was found at a slightly higher concentration than reported previously (Taylor et aL, 1989). Heptachlor epoxide was detected for the first time and found at a low concentration. An initial testing for alpha-, beta- and gamma-HCH detected concentrations similar to those in other Bering Sea pinnipeds. Mean summation of PCB was 0.45 microg g(-1) wet weight in males and 0.16 microg g(-1) in females; only one sample was > 1 microg g(-1). Traces of aliphatic hydrocarbons were detected in all sampled animals, only pristane (x = 0.48 microg g(-1)) was found in concentrations > 1 microg g(-1). Small sample sizes, a lack of samples from immature animals, and uniformly low concentrations of contaminants precluded meaningful analysis of age-related effects and regional differences.  相似文献   

内华达州洪堡县沿Getchell Trend浸染状金矿床周围地下水和冲积物中的…     

Grim.  DJ  王芳 《物探化探译丛》1994,(3):65-67

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从重晶石锶同位素研究认识塔斯马尼亚贱金属矿化的成因     

Whit.  DJ 梁智敏 《地质科学译丛》1993,10(2):52-57

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