湘东北中生代望湘花岗岩体岩石地球化学特征及其构造环境   总被引：9，自引：0，他引：9       下载免费PDF全文

贾大成  胡瑞忠  赵军红  谢桂青 《地质学报》2003,77(1):98-103

华南中生代构造由早期的挤压转为晚期的拉张,确定这种构造转折时期对认识华南大地构造演化具有重要意义。花岗岩的多期次侵入往往是不同构造环境的产物,不同构造环境花岗岩表现出岩石地球化学组成上的差别。本文对湘东北望湘花岗岩体不同期次岩石地球化学研究后,认为257～165 Ma,151～144 Ma,135～128 Ma 3个侵入期的花岗质岩石分别在TiO_2,K/Rb,Rb/Sr,∑REE,δEu及微量元素组成上存在较大的差异,反映为不同的产出构造环境,分别代表印支期的挤压构造环境、燕山早期的剪切—走滑环境和燕山晚期的伸展—滑脱环境。J_3—K_1(140 Ma±)是挤压—剪切与伸展—拉张构造环境的转折期,前者表现为岩石圈增厚,后者表现为岩石圈减薄,湘东南大规模金属及铀矿的形成多与岩石圈减薄期花岗质小岩体有成因联系。  相似文献   

吉林红旗岭地区含矿与不含矿岩体的地质地球化学对比   总被引：4，自引：0，他引：4       下载免费PDF全文

柴社立  任洪茂  申庆贵  王大勇 《地质找矿论丛》2003,18(4):229-232

吉林红旗岭地区是我国岩浆型铜镍硫化物矿床的主要矿化集中区之一。在区内已发现的镁铁质一超镁铁质岩体中，有的含有铜镍矿床或铜镍矿化，有的则不含矿。通过本区含矿与不含矿岩体的形成时代、岩石组合、橄榄石矿物成分、岩石化学成分和微量元素组合特征的对比，建立起镁铁质-超镁铁质岩体含镍性的评价标志，为隐伏岩体和新发现岩体含矿性的评价提供了理论依据。  相似文献   

晚更新世以来潍河古河道沉积及其对现代咸水入侵的控制   总被引：7，自引：0，他引：7  

刘恩峰  张祖陆  沈吉  杨丽原 《高校地质学报》2003,9(1):47-53

在莱州湾潍河古河道沉积区选取4条典型的地质剖面，对典型钻孔岩芯进行粒度、^14C及热释光测年分析，结合野外实地考察及100余个地质钻孔资料的分析，揭示了潍河晚更新世以来古河道的沉积特征。沉积剖面自下而上沉积物粒度逐渐减小，潍河以东古河道砂层厚30－50m，连续性好；潍河以西古河道砂层厚度小于20m，连续性较差。沉积特征的不同导致潍河以东地区咸水入侵发生早，后期变缓，为上淡下咸二层水文地质体；潍河以西地区咸水入侵主要是20世纪70年代末期以来在人类活动的干预下大规模的入侵，沿古河道入侵距离可达9－10km，为淡－咸－淡三层水文地质体。研究古河道沉积与咸水入侵的关系，为咸水入侵的发展趋势及防治措施的研究提供了重要科学依据。  相似文献   

金宝山铂族元素矿床铂族元素的热液活动研究   总被引：8，自引：3，他引：8  

陶琰  朱丹  高振敏  罗泰义 《矿物岩石地球化学通报》2003,22(1):32-37

金宝山铂族元素矿床是典型的岩浆型矿床，但矿体中广泛发育热液脉状矿石，脉体有较高的铂族元素含量，特别是硫化物细脉为铂族元素的重要载体，反映铂族元素的热液活动。根据岩体主要蚀变类型，区分出岩浆晚期高温流体活动阶段、岩浆期后蛇纹石化阶段和低温碳酸盐化阶段。各阶段热液性质、流体来源及铂族元素热液活动性分析表明，蛇蚊石化阶段铂族元素热液活动最强烈，主要表现为就地改造；热液活动未造成矿体形态、产状的根本变化。  相似文献   

Petrochemical evidence for off-ridge magmatism in a back-arc setting from the Yakuno ophiolite, Japan   总被引：2，自引：0，他引：2  

Yuji Ichiyama  Akira Ishiwatari 《Island Arc》2004,13(1):157-177

Abstract The Permian ophiolite emplaced in the Yakuno area, Kyoto Prefecture, consists of metavolcanic sequences, metagabbro and a troctolitic intrusion. The metavolcanics are associated with thick mudstone through a contact that shows the flowage of lava over unconsolidated mud layers on the sea floor. The metavolcanics and metagabbro have rare earth element (REE) patterns that are similar to enriched (E)‐ and transitional (T)‐types ([La/Yb]_N = 0.77–11.2) of mid‐oceanic ridge basalts (MORB), whereas their Nb/La ratios (0.40–1.20) are as low as those of back‐arc basin basalts (BABB). Cr‐spinels in the metavolcanic rocks have Cr? of 40–73 and an Fe³⁺? of 9–24, numbers which are comparable to the values of BABB. These lines of evidence suggest that the Yakuno ophiolite originated more likely from an early stage back‐arc basin rather than from an oceanic plateau, as has been suggested by some researchers. The troctolitic body that intrudes as a 0.5‐km long lens in the metagabbro is composed of troctolite, olivine gabbro and microgabbro. The troctolite is marked by an olivine–plagioclase crystallization sequence, different from the commonly observed olivine–clinopyroxene sequence in other mafic/ultramafic cumulates of the Yakuno ophiolite. The microgabbro, with a composition close to that of the parental magma of the troctolite, is depleted in light REE ([La/Yb]_N = 0.18–0.55) so that it has an REE pattern that mimics normal (N)‐type MORB. The interstitial clinopyroxene of the troctolite has highly variable TiO₂ contents (0.2–1.4 wt%), which is interpreted to result from postcumulus crystallization of heterogeneous intercumulus melts. The troctolitic intrusion may represent a late stage intrusion that formed in an off‐ridge environment during sea floor spreading of the back‐arc basin. The geochemical variation observed in the Yakuno ophiolite, ranging from N‐ to E‐MORB affinities, reflects the changes in both mantle source compositions and processes involved in magma generation during the evolution of the back‐arc basin.  相似文献   

开合构造环境下花岗岩体的构造样式与变形差异   总被引：1，自引：0，他引：1  

杨坤光徐亚军  杨奎锋刘强 《地质通报》2004,23(3):246-249

传统研究认为，大量花岗岩体的侵入发生于区域性伸展环境，是碰撞造山后应力松弛阶段侵位的，称之为造山后或非造山侵入体。近年来，对造山带和古岩浆弧的深入研究发现，花岗岩不但可以侵位于伸展构造环境，也可侵位于挤压构造环境(同构造侵入体)，两者在三维窄间形态、宏观尺度、露头尺度、显微尺度上的构造样式与变形往往是不同的。区分2类不同构造样式的岩体，对于分析区域构造和造山带演化有着重要的意义。  相似文献   

Prediction of slope water intrusion into the Kii channel in summer     

Toshinori Takashi  Tateki Fujiwara  Toshiaki Sumitomo  Wataru Sakamoto 《Journal of Oceanography》2006,62(1):105-113

Intrusions of the warm, oligotrophic surface slope water (SSW) and the cold, nutrient-rich bottom slope water (BSW) from the continental slope influence the annual variations in water temperature and nutrient concentrations in the Kii Channel in August. In order to evaluate the relationships between both these intrusions and the distance of the Kuroshio axis from Cape Shionomisaki (Kuroshio distance), a Distance-Intrusion-Diagram (DID) for temperature, which can reproduce the vertical temperature profile of the channel, was constructed by analyzing the temperature and Kuroshio distance records in August for 1967–2001. DIDs for nutrients (nitrate and phosphate) are also constructed by using the relationship between the nutrient concentration and water temperature. The only explanatory variable in the DIDs is the Kuroshio distance. The DID for temperature predicts that the SSW occupies almost the entire water column when the Kuroshio approaches Cape Shionomisaki (Kuroshio distance = 18.5 km). When the Kuroshio distance lies in the range 18.5–74 km, the BSW thickness increases proportionally to the Kuroshio distance increment while the SSW thickness decreases. The BSW occupies the largest portion of the channel when the Kuroshio distance is 74 km. Further, beyond 74 km, the BSW thickness reduces gradually. Yearly variations in the temperature and concentrations of nitrate and phosphate were hindcast with the DIDs. The results revealed that the Kuroshio distance contributes 70%, 35%, and 30% of the variances in temperature, nitrate concentration, and phosphate concentration, respectively.  相似文献   

Comment on “A note on salt intrusion in funnel-shaped estuaries: Application to the Incomati estuary, Mozambique” by     

Hubert H.G. Savenije   《Estuarine, Coastal and Shelf Science》2006,68(3-4):703

A comment is provided on the paper by Brockway et al. (2006. A note on salt intrusion in funnel-shaped estuaries: application to the Incomati estuary, Mozambique. Estuarine, Coastal and Shelf Science 66, 1–5) on a simple method to determine the salt intrusion in the Incomati estuary. Although this method is able to describe the salt intrusion in the Incomati reasonably well with only limited information, it is demonstrated that with the same data, but a more up-to-date methodology, a better and generally applicable equation could have been obtained.  相似文献   

海水入侵问题理论与实践   总被引：4，自引：1，他引：4  

邱汉学  张维冈 《海洋湖沼通报》1993,(4):20-27

本文综述了海水入侵的机理，入侵引起的生态变化及模型化、计算方法的研究现状、已发生入侵区的治理措施，指出了目前研究中存在的问题并探讨了今后的研究方向。  相似文献   

New type of pycnostad in the western subtropical-subarctic transition region of the North Pacific: Transition Region Mode Water     

Hiroko Saito  Toshio Suga  Kimio Hanawa  Tomowo Watanabe 《Journal of Oceanography》2007,63(4):589-600

A new type of pycnostad has been identified in the western subtropical-subarctic transition region of the North Pacific, based on the intensive hydrographic survey carried out in July, 2002. The potential density, temperature and salinity of the pycnostad were found to be 26.5–26.7 σ _θ , 5°–7°C and 33.5–33.9 psu respectively. The pycnostad is denser, colder and fresher than those of the North Pacific Central Mode Water and different from those of other known mode waters in the North Pacific. The thickness of the pycnostad is comparable to that of other mode waters, spreading over an area of at least 650 × 500 km around 43°N and 160°E in the western transition region. Hence, we refer to the pycnostad as Transition Region Mode Water (TRMW). Oxygen data, geostrophic current speed and climatology of mixed layer depth in the winter suggest that the TRMW is formed regularly in the deep winter mixed layer near the region where it was observed. Analysis of surface heat flux also supports the idea and suggests that there is significant interannual variability in the property of the TRMW. The TRMW is consistently distributed between the Subarctic Boundary and the Subarctic Front. It is also characterized by a wide T-S range with similar density, which is the characteristic of such a transition region between subtropical and subarctic water masses, which forms a density-compensating temperature and salinity front. The frontal nature also tends to cause isopycnal intrusions within the pycnostad of the TRMW.  相似文献