皖南和赣东北蛇绿岩成因及其构造意义：元素和Sm－Nd同位素制约   总被引：32，自引：0，他引：32  

赵建新  李献华  周国庆  邢凤鸣 《地球化学》1995,(4)

本文对扬子块体南缘构造侵位于板溪群（及相应地层）的皖南和赣东北晚元古代蛇绿岩进行了系统的元素和Ｓｍ－Ｎｄ同位素地球化学研究，结果表明两套蛇绿岩具有类似的元素地球化学特征，即二者的火山岩元素地球化学特征均类似于形成于弧后盆地构造环境的拉斑玄武岩。但是，两套蛇绿岩的Ｎｄ同位素组成明显不同。赣东北蛇绿岩具有相当均一的高εＮｄ（Ｔ）值（＋５．５±１．２），表明来源于一较亏损的上地幔源区，并且没有受到明显的较成熟地壳物质的混染。相反，皖南蛇绿岩的εＮｄ（Ｔ）值低，并有较大的变化范围（＋４．５──１．０），并和Ｓｍ／Ｎｄ、Ｎｄ、ＭｇＯ、ＳｉＯ２呈明显的二元混合相关关系，表明蛇绿岩是由亏损幔源岩浆（初始εＮｄ（Ｔ）≈＋５．５）在结晶分异过程中与地壳组分（初始εＮｄ（Ｔ）≈－１）混合形成的。皖南和赣东北蛇绿岩的Ｎｄ同位素和元素地球化学特征以及该地区的同时代花岗岩和火山岩的时空分布特征，可以用华南和扬子元古宙陆－弧－陆碰撞模式来解释。大约在１．０Ｇａ前，扬子和华南块体之间存在一多岛弧洋盆。大陆边缘岛弧和大洋岛弧在扬子块体南缘发育演化。皖南和赣东北蛇绿岩就是在大陆边缘盆地和弧间盆地演化过程中形成的洋壳构造侵位的碎片。该地区Ｉ型  相似文献   

内蒙古中西部多岛海构造演化   总被引：10，自引：0，他引：10  

高计元  王一先  裘愉卓  张乾 《大地构造与成矿学》2001,25(4):397-404

内蒙古中西部大陆由一个微大陆、三条弧后盆地和三条火山岛弧,即华北微大陆、白云鄂 傅弧后盆地、白乃庙火山岛弧、温都尔庙弧后盆地、苏尼特左－锡林浩特火山岛弧、贺根山弧后盆 地和二连浩特－锡林郭勒火山岛弧组成。经过了长期而复杂的微大陆和火山弧的裂解、弧后盆地 的消减衰亡及弧－陆和弧－弧碰拉等构造演化,才最终形成今天所见到的这种构造样式。  相似文献   

六盘山典型植被类型土壤中石砾对大孔隙形成的影响   总被引：4，自引：1，他引：4  

时忠杰  王彦辉  熊伟  徐丽宏  于澎涛  徐大平 《山地学报》2007,25(5):541-547

六盘山山区土壤中存在大量的石砾,对土壤大孔隙的形成具有重要影响。为了深刻了解和评价土壤中石砾对大孔隙形成的可能作用,本研究分析了六盘山典型植被类型下土壤中的石砾体积含量、大孔隙度变异以及石砾体积含量对大孔隙度、大孔隙半径与密度的影响。结果表明,石砾含量增加导致土壤大孔隙的平均半径和体积增大,特别是导致半径大于1.4 mm的大孔隙密度的增大,但对较小半径的大孔隙密度影响不大;总体上,石砾对土壤大孔隙度的形成影响随土深的增加而越来越明显,说明六盘山地区土壤的大孔隙明显同时受到生物因素和石砾含量因素的影响。  相似文献   

基于小波变换的反射光谱分析在蛇绿岩识别中的应用研究——以西准噶尔地区为例     

赵同阳  周可法  张晓帆  陈川  徐仕琪 《西北地质》2007,40(4):87-93

介绍了基于小波变换的反射光谱分析技术的基本理论和方法;运用此技术手段对克拉玛依市白碱滩区西侧地区40条岩石野外光谱曲线数据进行了定量处理,总结并分析了蛇绿岩套中常见典型岩石(基性混杂岩、辉长岩、橄榄岩、蛇纹石)的光谱特征及其产生原因。最后,结合ETM 波段范围提出了适用于西准噶尔地区多波段遥感影像光谱角(Spectral Angle Mapper,SAM)提取模型,从遥感影像上识别蛇绿岩分布奠定了良好的基础。  相似文献   

Geochemistry and spatial distribution of OIB and MORB in A’nyemaqen ophiolite zone: Evidence of Majixueshan ancient ridge-centered hotspot   总被引：2，自引：0，他引：2  

Guo AnLin  Zhang GuoWei  Sun YanGui  Zheng JianKang  Liu Ye  Wang JianQi 《中国科学D辑(英文版)》2007,50(2):197-208

The mafic volcanic association is made up of OIB, E-MORB and N-MORB in the A'nyemaqen Paleozoic ophiolites. Compared with the same type rocks in the world, the mafic rocks generally display lower Nb/U and Ce/Pb ratios and some have Nb depletion and Pb enrichment. The OIB are LREE-enriched with (La/Yb)N =5―20, N-MORB are LREE-depleted with (La/Yb)N = 0.41―0.5. The OIB are featured by incompatible element enrichment and the N-MORB are obviously depleted with some metasomatic effect, and E-MORB are geochemically intermediated. These rocks are distributed around the Majixueshan OIB and gabbros in a thickness greater than a thousand meters and transitionally change along the ophiolite extension in a west-east direction, showing a symmetric distribution pattern as centered by the Majixueshan OIB, that is, from N-MORB, OIB and E-MORB association in the Dur'ngoi area to OIB in the Majixueshan area and then to N-MORB, OIB and E-MORB assemblage again in the Buqingshan area. By consideration of the rock association, the rock spatial distribution and the thickness of the mafic rocks in the Majixueshan, coupled with the metasomatic relationship between the OIB and MORB sources, it can be argued that the Majixueshan probably corresponds to an ancient hotspot or an ocean island formed by mantle plume on the A'nyemaqeh ocean ridge, that is the ridge-centered hotspot, tectonically similar to the present-day Iceland hotspot.  相似文献   

Geology and geochemistry of the Bingdaban ophiolitic mélange in the boundary fault zone on the northern Central Tianshan Belt,and its tectonic implications     

Dong YunPeng  Zhang GuoWei  Zhou DingWu  Luo JinHai  Zhang ChengLi  Xia LinQi  Xu XueYi  Li XiangMin 《中国科学D辑(英文版)》2007,50(1):17-24

The properties and tectonic significance of the fault bound zone on the northern margin of the Central Tianshan belt are key issues to understand the tectonic framework and evolutionary history of the Tianshan Orogenic Belt. Based on the geological and geochemical studies in the Tianshan orogenic belt, it is suggested that the ophiolitic slices found in the Bingdaban area represent the remaining oceanic crust of the Early Paleozoic ocean between the Hazakstan and Zhungaer blocks. Mainly composed of basalts, gabbros and diabases, the ophiolites were overthrust onto the boundary fault between the Northern Tianshan and Central Tianshan belts. The major element geochemistry is characterized by high TiO₂ (1.50%–2.25%) and MgO (6.64%–9.35%), low K₂O (0.06%–0.41%) and P₂O₅ (0.1%–0.2%), and Na₂O>K₂O as well. Low ΣREE and depletion in LREE indicate that the original magma was derived from a depleted mantle source. Compared with a primitive mantle, the geochemistry of the basalts from the Bingdaban area is featureded by depletion in Th, U, Nb, La, Ce and Pr, and unfractionated in HFS elements. The ratios of Zr/Nb, Nb/La, Hf/Ta, Th/Yb and Hf/Th are similar to those of the typical N-MORB. It can be interpreted that the basalts in the Bingdaban area were derived from a depleted mantle source, and formed in a matured mid-oceanic ridge setting during the matured evolutionary stage of the Northern Tianshan ocean. In comparison with the basalts, the diabases from the Bingdaban area show higher contents of Al₂O₃, ΣREE and HFS elements as well as unfractionated incompatible elements except Cs, Rb and Ba, and about 10 times the values of the primitive mantle. Thus, the diabases are thought to be derived from a primitive mantle and similar to the typical E-MORB. The diabases also have slight Nb depletion accompanying no apparent Th enrichment compared with N-MORB. From studies of the regional geology and all above evidence, it can be suggested that the diabases from the Bingdaban area were formed in the mid-oceanic ridge of the Northern Tianshan ocean during the initial spreading stage. Supported by the Major State Research Program of PRC (Grant No. 2001CB409801), the National Natural Science Foundation of China (Grant Nos. 40472115 and 40234041) and the State Research Program of China Geological Survey (Grant No. 2001130000-22)  相似文献   

Zircon SHRIMP U-Pb ages and trace element geochemistry of the Kuhai gabbro and the Dur''''ngoi diorite in the southern east Kunlun tectonic belt, Qinghai, Western China and their geological implications     

LI WangYe  LI ShuGuang  GUO AnLin  SUN YanGui  ZHANG GuoWei 《中国科学D辑(英文版)》2007,50(Z2):331-338

Timing of the intermediate-basic igneous rocks developed in the area of Kuhai-A'nyêmaqên along the southern east Kunlun tectonic belt is a controversial issue. This paper presents new zircon SHRIMP U-Pb dating data for igneous zircons from the Kuhai gabbro and the Dur'ngoi diorite in the Kuhai-A'nyemaqen tectonic belt, which are 555±9 Ma and 493±6 Ma, respectively. The trace element geochemical features of the Kuhai gabbro and the Dur'ngoi diorite are similar to those of ocean island basalts (OIB) and island arc basalts (IAB), respectively. Thus, the Kuhai gabbro with the age of 555±9 Ma and OIB geochemical features is similar to the Yushigou oceanic ophiolite in the North Qilian orogen, whereas the Dur'ngoi diorite with the age of 493±6 Ma and IAB geochemical features is similar to the island arc volcanic rocks developed in the north Qaidam. The Late Neoproterozoic to Early Ordovician ophiolite complex in the area of Kuhai-A'nyêmaqên suggests that the southern margin of the "Qilian-Qaidam-Kunlun" archipelagic ocean in this period was located in the southern east Kunlun tectonic belt. Therefore, the southern east Kunlun tectonic belt in the early Paleozoic is not comparable to the Mianlüe tectonic belt in the Qinling orogenic belt.  相似文献   

Geology and geochemistry of the Bingdaban ophiolitic mélange in the boundary fault zone on the northern Central Tianshan Belt, and its tectonic implications     

DONG YunPeng  ZHANG GuoWei  ZHOU DingWu  LUO JinHai  ZHANG ChengLi  XIA LinQi  XU XueYi  LI XiangMin 《中国科学D辑(英文版)》2007,50(1)

  相似文献   

新疆东昆仑阿其克库勒湖西缘地区蛇绿岩的确证   总被引：6，自引：0，他引：6  

吴峻  兰朝利  李继亮  俞良军 《地质科技情报》2001,20(3):6-10

新疆东昆仑阿其克库勒湖西缘出露了一套超基性—基性岩。该蛇绿岩的野外地质、岩石学以及岩石化学特征表明它们是由变质橄榄岩和堆晶岩两大单元组成的蛇绿岩 ,是否存在蛇绿岩的其它单元值得进一步研究。同时 ,这些特征表明其与青海东昆仑清水泉蛇绿岩相似 ,指示它们可能为同一洋壳的残余。  相似文献   

Soils and Land use on Lithologically Diverse Ophiolitic Alluvia on the Coastal Plain of Palawan,Philippines     

I .C. Baillie  N. B. Inciong  P. M. Evangelista 《Singapore journal of tropical geography》2001,22(1):1-14

The soils on the southeastern coastal plain of Palawan, Philippines are developed on alluvium derived from various lithologies of the Palawan Ophiolitic Complex. There is little lateral mixing of the alluvium. The soil pattern is interpreted as the result of increasing weathering and leaching with age on deposits of different lithological origins. In the ultramafic catchment the younger soils are infertile due to several unfavourable characteristics, including high contents of heavy metals and Mg, deficiencies of P and micro‐nutrients, and impermeability. These soils improve with increased weathering and leaching, and the older soils have better physical and Mg characteristics. In felsic alluvia the reverse is found, and the soils on younger deposits are the most fertile, while the older soils have unfavourable combinations of subsoil compaction, acidity and dominance by aluminium. These patterns are reflected in the current land use, with areas of sparse settlement and cultivation on the less fertile soils on younger ultramafic and older felsic alluvia. These areas have been avoided or abandoned, rather than overlooked, by farmers and cannot be considered as “empty lands”. Their sustainable development will require careful management. Most of the more fertile land is already cultivated.  相似文献