共查询到19条相似文献，搜索用时 93 毫秒
1.
鄂西-黔中陆缘坻是扬子地块东南缘晚震旦世陡山沱期磷块岩沉积成矿的构造古地理单元,其形态是向南东凸出的弧形,来自SE方向上升洋流抵达陆缘坻后,分成向NW和SW向两个方向洋流,磷块岩两个工业矿层随洋流方向发生有规律的迁移沉积,这在同一矿集区的不同矿段也表现出清晰的迁移沉积规律。由于陆缘坻本身古构造和古地形特点,决定了磷块岩成矿的具体位置,构成了不同的控矿模型,特别陆缘坻基底隆起迎向洋流的一侧是磷块岩大规模成矿的最佳地段,往往形成成群的大中小矿床,甚至形成超大型矿床。 相似文献
2.
海洋中磷的循环与沉积作用 总被引：1，自引：1，他引：1
磷在海洋中的循环与沉积主要是靠生物作用进行的。海洋表层水中的溶解磷几乎全部被海洋植物摄取，海洋植物及动物死亡后最终以生物碎屑的形式沉入海底，在其沉降和到达深层水的过程中大部分被分解、破坏，变成可溶组分又重新返回海水，使深层水中磷浓度提高。含磷浓度高的深层水被上升洋流带到表层后又被生物吸收，重复循环。当上升洋流抵达大陆边缘，特别是遇有陆缘坻存在时，磷等营养物质滞留，导致磷质生物大量繁衍，死亡后沉积，并经成岩作用，便形成大规模的工业磷块岩矿床 相似文献
3.
贵州晚前寒武世海相磷酸盐循环模式 总被引：1，自引：1，他引：1
被动大陆边缘向前陆（盆地）充填的构造背景，形成了台棚、缓坡、陆坡组成的古地理，提供了陆源磷和发育了磷酸盐循环的古海洋；冰期形成了下降洋流，引起陆源磷酸盐的迁移和深海溶解磷酸盐的富聚；三级相对海平面快速上升和发育于低纬度区的上升洋流，为各种磷块岩形成开拓了沉积场所和磷保证。 相似文献
4.
扬子地块陡山沱期与梅树村期磷矿区域成矿规律 总被引：11，自引：1，他引：10
扬子地块是我国重要的产磷区 ,陡山沱与梅树村两大成磷期磷块岩储量占全国磷矿储量的85 %。在多年来丰富的资料积累与研究基础上 ,经过实践—理论—再实践的认识过程 ,归纳与提练出具有共性和普遍适用的海相磷块岩区域成矿规律 ,上升成为理性认识 ,因而具有很强的实用性 ,可作为成矿预测的准则。这些规律有 :含磷岩系规律、磷矿层规律、磷块岩自然类型规律、磷块岩结构类型规律、磷块岩矿物与化学成分规律、磷块岩序列规律、磷块岩成矿的构造古地理规律、陆缘坻含磷岩组规律、磷块岩富集规律等。并在此基础上划分出扬子地块的 2个三级成矿亚带和若干四级成矿区。 相似文献
5.
川西南雷波卡哈洛磷矿床位于扬子准地台上扬子台褶带美姑-金阳陷褶束的中段,划属川西南成磷带雷波聚磷区,是典型的昆阳式沉积型磷块岩矿床,磷矿层赋存于下寒武统麦地坪组,通过对该区古构造、古沉积环境和古气候特征等的分析研究,认为古微地形地貌对矿体有良好的控制作用,提出"陆缘坻、古沉积环境、古气候与古微地貌"四位一体的成矿模式。这对研究区生产勘探工作具有一定的指导意义。 相似文献
6.
中国扬子地台西缘寒武纪风暴事件与磷矿沉积 总被引：7，自引：2，他引：7
中国扬子地台及邻区海域,在早寒武世至中寒武世早期,风暴活动频繁,地理位置由西向东,由南向北,地层层序自下而上三个组段发现有风暴岩和风暴沉积物,其中以下寒武统梅树村组的磷质风暴岩最典型。风暴活动冲击川滇岛陆及牛首山岛陆的内侧,从而使两个岛陆间的海面下降,造成外海海水填充并形成上升洋流。富磷海水随着上升洋流运移,为磷质沉积提供来源。因此,风暴和风暴流作用不仅形成和加速了上升洋流的循环和补给,同时又是磷矿簸选富集的物理驱动力。风暴流向海的流动和上升洋流通过的方向,沿着扬子地台西缘形成了我国重要的磷质富集带与工业磷矿分布区。 相似文献
7.
新疆阿尔泰哈巴河一带古生代火山岩的形成与演化 总被引：4，自引：0，他引：4
文中详细地论述了新疆阿尔泰哈巴河一带古生代火山岩的地质，岩石化学，稀土元素地球化学特征，将其分为三个类型，认为火山岩是在陆缘裂陷槽的区域构造背景下发生和演化的，对各类型火山岩岩浆来源，上升模式也做了初步讨论。 相似文献
8.
大陆岩石圈和大洋岩石圈有着深刻的差别，运用板块构造理论和模式研究大陆岩石圈会遇到许多特殊的问题。本文从陆缘演化和多个板块构造旋回叠加两方面做了初步探讨，提出岩浆型被动陆缘是独立的一类古陆缘；在辨认后续板块构造旋回叠加中，新构造成分和格局的确定有重要意义。本文还讨论了汲取大陆地质研究经验，在新的学科水平上重新解释传统大地构造学中一些有用概念的意义。 相似文献
9.
浏阳永和磷矿沉积环境与成矿机理 总被引：1，自引：0，他引：1
永和磷矿的磷质主要来自南华洋前湘锰期的海底火山活动 ,上升洋流是磷质运移的主要营力。根据本区的 2个冰海—含磷建造的旋回组合特征 ,本文提出了“冰期磷质储集库”的新解说 ,揭示了“大冰期成磷说”的内涵机理。 相似文献
10.
上扬子地区下寒武统海相富有机质页岩形成环境与主控因素分析 总被引：3，自引：0，他引：3
对上扬子地区下寒武统富有机质页岩发育主控因素的研究是进行该区页岩气勘探有利区预测的基础问题之一。通过对上扬子地区下寒武统黑色页岩典型露头剖面样品特征的分析,运用岩石、矿物、有机质特点、特征元素等指标对该区海相富有机质页岩在早寒武世时的古环境进行恢复,建立上扬子地区下寒武统海相富有机质页岩沉积环境判别综合表,认为该套黑色页岩在早寒武世是典型的缺氧环境。上扬子地区下寒武统富有机质页岩的发育是古构造、古气候和古海平面变化、古洋流及海底热液活动等因素综合作用的结果。建立了上扬子地区古海平面上升―上升洋流―热液活动―水体分层―缺氧环境的页岩发育模式,指出海底热液活动和上升洋流促进生物体的勃发,为富有机质页岩形成提供物质基础;海平面上升和上升洋流不仅造成水体分层,而且共同影响富有机质页岩的分布范围。 相似文献
11.
豫西石炭系铝土矿出露位置的控制因素 总被引：1，自引：0，他引：1
陈旺 《大地构造与成矿学》2007,31(4):452-456
豫西石炭系铝土矿形成于华北古夷平面上,沉积于华北陆表海-湖泊环境中。豫西石炭系铝土矿围绕隆起区分布及太原组海陆交互相的沉积特征,使人认为铝土矿形成于古陆边缘。本文通过对豫西铝土矿的区域地质背景、含矿岩系特征及其形成的古地理环境以及典型矿区地质构造的综合分析认为,豫西石炭纪"古陆"并不存在,豫西的现代地貌和石炭纪有天壤之别,新生代以来的构造运动是豫西铝土矿出露定位的控制性因素,豫西铝土矿围绕隆起区分布的特征是后期、尤其是新生代以来的构造运动造成的。 相似文献
12.
Currently ranking as the largest producer of gold in the world, China's gold reserves are spread over 200 major gold deposits and several minor deposits. A large part of these belong to the late Mesozoic gold deposits in the North China Craton (NCC) that occur along craton margins, as well as within the cratonic interior in reactivated paleo sutures, and show a close spatio-temporal relationship with zones of lithospheric thinning and craton destruction. Here we integrate and evaluate geophysical information from the NCC through an analysis of receiver function and tomography that suggest mantle upwelling accompanied by lower crustal or lithospheric delamination. Our results identify that the major gold belts in the NCC are largely located above zones of mantle upwelling and craton destruction. The faults and paleo sutures provided the pathways for migration of ore-bearing fluids, with the granitoids offering favorable conditions for gold deposition. 相似文献
13.
Matthias Tomczak 《Geoforum》1981,12(2):179-191
The use of terms such as Benguela Current or Peru Current System for different features of the oceanic circulation in the eastern parts of the oceans is reviewed. During 50 years of upwelling research these terms have been used for different oceanographic phenomena. It is argued that one reason for inconsistent use has been that names of currents were chosen on geographic rather than hydrodynamic principles, and that although knowledge of the dynamics of current systems expanded, it became increasingly difficult to modify the existing nomenclature accordingly. In order to provide a basis for a unified terminology, the dynamics of ocean currents in the eastern pans of the oceans are reviewed. It is argued that the coastal upwelling current system is a modification of the inshore part of the eastern boundary current and consequently should not be named as opposed to it but as part of it. It is suggested that the traditional geographic names be used for the eastern boundary currents and new names be assigned by international agreement to the coastal upwelling currents. 相似文献
14.
This study focuses on storm deposits in the Muschelkalk facies of the Betic Cordillera (southern Spain) and interprets their deposition mechanisms. Three types of storm deposit are distinguished: (i) pot/gutter casts; (ii) tempestite beds; and (iii) storm‐winnowed deposits. Each deposit provides information about the carbonate platform environment in which it was deposited. The tempestite models proposed are: (i) the bypass‐zone tempestite model, occurring in a muddy ramp at the epicontinental basin margin. This model is characterized by potholes and gutters that form in a shoreline bypass‐zone during storms; (ii) the gradient‐current tempestite model in which frequent tempestite beds are related to storm gradient currents. Thickness and grain size decrease towards the deep distal ramp; and (iii) the winnowed deposit tempestite model whereby storm deposits are winnowed and deposited in the same environment with only short lateral transport having occurred. This model evokes more restricted and shallower conditions, lagoons or inland seas. The distribution of all these deposits in the stratigraphic sections studied corroborate the eustatic third‐order cycle identified, although the different features of the storm deposits and their positions in each section indicate a subsidence varying in time and space. In the transgressive stage, the margins of the epicontinental basin were a well‐developed ramp with potholes and gutters. In contrast, during the high sea‐level stage, storm deposits generated tempestite beds or storm‐winnowed deposits in the different areas. The epicontinental carbonate platform with ramp edges evolved into a complex depositional system of coastal and shallow‐marine environments with lagoons and restricted inland seas. Thus, the epicontinental platform underwent substantial change from the Late Anisian to the Late Ladinian and this is reflected in its storm deposits. 相似文献
15.
斑岩型钼矿床的形成机制与地球化学过程 总被引：1，自引：1，他引：0
斑岩型钼矿床是世界钼矿床中最重要的种类,其中90%以上的钼矿床都和斑岩有关。斑岩型钼矿床主要分布于环太平洋成矿带和特提斯成矿带上,主要与板块俯冲过程有关,可以分为斑岩铜钼矿床、高氟型斑岩钼矿床和低氟型斑岩钼矿床。我们通过对全球斑岩型钼矿床的时空分布与钼元素地球化学性质分析,认为斑岩型钼矿床的物质来源是钼元素通过表生地球化学作用进行初始富集后形成的富钼沉积物。新元古代晚期(750～542Ma)大气氧再次升高之后,富钼的黑色页岩等才大量出现,因此斑岩型钼矿床主要形成于500Ma之后。富钼黑色页岩等沉积物在板块俯冲过程中脱水,形成富含Mo和Re的变质流体,同时两者发生分异。这种变质流体交代上覆地幔楔使Mo和Re留存在其中。随着俯冲洋壳的部分熔融,形成富Cu(Au)的岩浆,穿过富含Re(Mo)的上覆地幔楔,形成斑岩型铜钼矿床,因此这类矿床的辉钼矿Re含量更高。而随后出现的板块后撤,使软流圈上涌,板片上大量多硅白云母分解,形成了富含F的岩浆,穿过富含Mo的上覆地幔楔,进而形成高氟型斑岩矿床。低氟型钼矿床很可能与俯冲关系较小,富钼沉积物通过造山过程被深埋,在适当的条件下形成低氟型斑岩钼矿床。 相似文献
16.
论内源盆地动力场及磷块岩富集作用的动力学分析 总被引：4，自引：1，他引：4
内源盆地泛指非陆源沉积盆地。其最终沉积方式和展布格局受物理、物理化学、生物化学、生物物理等多种动力场的制约;沉积作用场包括各种直观性和背景性的动力学过程,这种过程由其性质、作用方式、方向强度和变化梯度所决定。就沉积磷矿而言,从全球冰室效应期向温室效应期的突变是引起大洋磷酸盐富集的主因;与这一转变过程相联系的二级或三级最大海泛事件及其伴生洋流上翻就是富集成磷块岩的沉积动力场。中国晚震旦世、早寒武世巨型磷块岩建造便是其明显例证,其磷块岩层序的向上变浅的特征和微相变化特征都是高频率海平面变化动力场(即米兰柯维奇事件)的历史记录,也反映出巨型磷块岩建造具有多级次多旋回沉积特征。 相似文献
17.
Using some uranium deposits and recent U-bearing sediments as examples, it is shown that all U-bearing rocks are characterized by an association of organic matter and calcium phosphate, irrespective of the quantitative relationship between these components. A considerable proportion of these components was delivered into sediments with remains of marine planktonic and nektonic organisms. Along with organic matter, calcium phosphate played a significant role in uranium concentration. This is related to a high sorption ability of the calcium phosphate. Uranium accumulated during diagenesis as a result of diffusion exchange between bottom and interstitial waters. The combination of anoxic bottom environment with high bioproductivity in upper aerated waters, a typical phenomenon in oceanic upwelling zones, is the most favorable factor of uranium concentration in the sedimentary process. This determines the stable paragenetic association of organic matter, phosphorus, and uranium in marine sediments, such as black shales and organogenic phosphate deposits. 相似文献
18.
Here we describe a mosasaurid from the upper Maastrichtian Quiriquina Formation near the town of Cocholgüe about 30 km north of Concepción, central Chile. The specimen comprises a concretion preserving the rostral part of a pair of mandibular rami. The bulbous base of the teeth allows referral to cf. Plotosaurus sp. This is southernmost record of this piscivorous and pelagic taxon. The southern dispersal of mosasaurs during the late Maastrichtian may not only have depended from warm south-bound Equatorial currents but mainly from the nutrient-rich oceanic regime along an upwelling zone of cold abyssal water that mixed with the warm surface water, resulting in an enormous primary production. Apparently mosasaur dispersal depended more on food than on suitable temperatures or currents. 相似文献
19.
《Gondwana Research》2014,25(3-4):1080-1090
Geological studies have suggested that a significant amount of crustal material has been lost from the surface due to delamination, continental collision, and subduction at oceanic–continental convergent margins. If so, then the subducted crustal materials are expected to be trapped in the mid-mantle due to the density difference from peridotitic materials induced by the phase transition from coesite to stishovite. In order to study the effect of the subducted granitic materials floating around the mantle transition zone, we conducted two-dimensional numerical experiments of mantle convection incorporating a continental drift with a heat source placed around the bottom of the mantle transition zone. The simulations deal with a time-dependent convection of fluid under the extended Boussinesq approximation in a model of a two-dimensional rectangular box with a height of 2900 km and a width of 11,600 km, where a continent with a length of 2900 km and heat source below the continent are imposed. We found that the addition of heat source in the mantle transition zone considerably enhances the onset of upwelling plumes in the upper mantle, which further reduces the time scale of continental drift. The heat source also causes massive mechanical mixing, especially in the upper mantle. The results suggest that the heat source floating around the mantle transition zone can be a possible candidate for inducing the supercontinent cycle. 相似文献