赣东北蛇绿混杂岩中尖晶石环带特征及其地质意义
发布时间：2019-07-06 08:26
【摘要】：本文对赣东北蛇绿混杂岩中环带状的尖晶石进行了深入的矿物学研究,结合地幔橄榄岩和玄武岩进行地球化学分析,并综合尖晶石的共生矿物特征,进而揭示尖晶石微区环带特征与其所经历的深部地质过程之间的耦合关系,探讨其地质意义。论文取得以下几点认识:(1)识别出了3种产状的尖晶石:①部分蚀变状尖晶石,呈黑色和红褐色不规则状,Cr#值为20.25~38.39,指示为深海橄榄岩的残余体,估算部分熔融程度为8%~11%;②环带状尖晶石,呈粒状分布在蛇纹岩中,Cr#值介于45.36~49.53之间,指示洋内俯冲环境;③有孔状尖晶石,呈浸染状和粒状,表面具孔隙发育,高Cr#值(介于48.39~69.90之间)特征反映岛弧环境,指示后期碰撞造山作用;(2)环带状尖晶石的主、微量元素含量表明从核心到边缘,Fe O、Ga、Ni和Ti含量增加,Al2O3、Mg O、Cr2O3、V、Co和Mn含量减少;(3)俯冲作用的流体交代导致了尖晶石环带的形成,从核心到边缘发生元素的重新分配。流体交代过程中会使尖晶石中的主要成分Al2O3和Mg O发生转移,在这期间产生了绿泥石充填在孔隙中;随着氧化流体渗透进一步加强,尖晶石空孔隙中富Cr2+和Fe2+的流体会导致尖晶石中八面体配位和四面体配位的Fe3+、Fe2+重新排序,同时Zn、Co、Mn和Fe2+等元素可进入Mg2+空出的四面体配位中,而Ni2+、Ga3+、Sc3+和Ti4+等元素可进入Al3+空出的八面体配位中,从核心向边缘的规律分布导致环带的形成;(4)流体在环带尖晶石的形成上起到重要作用,而地幔橄榄岩中的流体来源与构造环境息息相关,研究表明赣东北蛇绿混杂岩中地幔橄榄岩具亏损地幔源区的特征,为原始地幔熔融残留物,并显示有陆源物质的混染,可能受消减作用的影响;(5)根据尖晶石环带特征及区域构造过程,对尖晶石环带成因认识如下:1100Ma~1000Ma洋壳发育阶段,具MORB特征的玄武岩产出,在洋中脊深海橄榄岩形成尖晶石;1000Ma~890Ma期间,伴随古华南洋向扬子块体俯冲,处于岛弧之下的地幔楔发生部分熔融,洋内俯冲带流体交代致使尖晶石发生部分蚀变形成环带状尖晶石,流体进一步蚀变改造,并最终形成有孔状尖晶石;890Ma~850Ma期间,洋壳进一步俯冲使华夏板块与扬子板块在绍兴-江山-萍乡一带碰撞拼贴,产生的构造应力作用使赣东北蛇绿岩发生NW向褶皱变形,导致有孔状尖晶石具裂隙发育;850Ma~800Ma阶段区域发生大规模的岩浆活动,对尖晶石微区的影响不明。尖晶石具有岩石成因的指示意义,为探讨蛇绿岩的成因提供直接的矿物学证据。本文对赣东北蛇绿混杂岩中环带状尖晶石的研究表明尖晶石对蛇绿岩的形成和演化过程具有记录作用,可以反映岩石经历的深部地质过程。此外,本文对环带状尖晶石只是初步研究,在后续研究工作中可以对尖晶石微区中的微量元素、同位素、流体来源做进一步系统的分析研究,揭示尖晶石微区中元素的分布规律,限定流体性质以及矿物形成时温度、压力、氧逸度等物理化学信息。
[Abstract]:In this paper, an in-depth mineralogical study of the banded spinels of the middle ring of the ophiolitic melange in the northeast of Jiangxi is carried out, and the geochemical analysis of the ground-derived peridotite and the basalt is carried out, and the characteristics of the intergrowth of the spinel are integrated. Furthermore, the coupling relation between the characteristics of the spinel micro-zone and its deep geological process is revealed, and its geological significance is discussed. The following recognition is made in this paper: (1) Three types of spinel are identified: a partially altered spinel, a black and reddish-brown irregular shape, a Cr # value of 20.25-38.39, a residual body indicated as deep-sea peridotite, an estimated partial melting degree of 8-11%, and a ring-like spinel, In the granites, the Cr # value is between 45.36 and 49.53, which indicates the subduction environment of the ocean; the pore-like spinel is in the form of disseminated and granular, and the surface has pore development, and the high Cr # value (between 48.39 and 69.90) reflects the island arc environment and indicates the post-collision orogeny; (2) The contents of the main and trace elements of the ring-shaped spinel show that the content of Fe O, Ga, Ni and Ti is increased from the core to the edge, and the content of Al2O3, Mg O, Cr2O3, V, Co and Mn is reduced; and (3) the subduction of the fluid has led to the formation of the spinel belt. The redistribution of elements from the core to the edge. During the fluid metasomatic process, the main components Al2O3 and Mg O in the spinel are transferred, during which the chlorite is filled in the pores, and as the oxidation fluid penetration is further strengthened, The rich Cr2 + and Fe 2 + in the spinel hollow pores can lead to the octahedral coordination of the spinel and the Fe3 + and Fe2 + re-ordering of the tetrahedra, while the elements such as Zn, Co, Mn and Fe 2 + can enter the tetrahedrally coordinated with Mg2 +, while Ni2 +, Ga3 +, elements such as Sc3 + and Ti4 + can enter the octahedral coordination vacated by Al3 +, and the distribution of the regular distribution from the core to the edge leads to the formation of the endless belt; and (4) the fluid plays an important role in the formation of the annular spinel, and the source of the fluid in the ground peridotite is closely related to the construction environment, The study shows that the characteristics of the ground-and-ground olive-rock in the North-East and North-East snake-green hybrid rock are characterized by the loss of the source region, which is the original melting residue, and shows that the mixed-dyeing of the land-source material can be affected by the reduction effect; and (5) according to the characteristics of the spinel belt and the process of the regional construction, The genetic understanding of the spinel belt is as follows: at the stage of the development of the oceanic crust at the stage of 1100 Ma ~ 1000 Ma, the basalt output with the characteristics of the MOB, the spinel in the deep-sea peridotite in the ocean, and the subduction of the Yangtze block with the southern ocean of the ancient China during the period of 1000 Ma ~ 890 Ma, and the partial melting of the geodesic wedge under the island arc. in that period of 890-850 Ma, the oceanic crust further subduction to make the Cathaysian plate and the Yangtze plate collide with the Yangtze plate in the area of Shaoxing-Jiangshan-Meixiang, The tectonic stress produced in the northeast of Jiangxi resulted in the NW-to-fold deformation of the ophiolite in the northeast Jiangxi, resulting in the fracture development of the pore-like spinels, and the large-scale magmatism in the region of the 850-800 Ma phase region, and the influence on the spinel micro-domains is unknown. The spinel has the indication of the origin of the rock, and provides a direct mineralogical proof for exploring the origin of the ophiolite. In this paper, the study of the banded spinels of the middle ring of the ophiolite in the northeast of Jiangxi shows that the formation and evolution of the spinel has a record effect on the formation and evolution of the ophiolite, which can reflect the deep geological process of the rock's experience. In addition, this paper is a preliminary study on the ring-shaped spinels. In the follow-up study, the trace elements, isotopes and fluid sources in the spinel micro-domains can be analyzed and studied, and the distribution rule of the elements in the spinel micro-domains is revealed. Physical and chemical information such as temperature, pressure, oxygen fugacity, etc. when the fluid property and the mineral formation are defined.
【学位授予单位】：东华理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P578.46;P588.1
本文编号：2510897
[Abstract]:In this paper, an in-depth mineralogical study of the banded spinels of the middle ring of the ophiolitic melange in the northeast of Jiangxi is carried out, and the geochemical analysis of the ground-derived peridotite and the basalt is carried out, and the characteristics of the intergrowth of the spinel are integrated. Furthermore, the coupling relation between the characteristics of the spinel micro-zone and its deep geological process is revealed, and its geological significance is discussed. The following recognition is made in this paper: (1) Three types of spinel are identified: a partially altered spinel, a black and reddish-brown irregular shape, a Cr # value of 20.25-38.39, a residual body indicated as deep-sea peridotite, an estimated partial melting degree of 8-11%, and a ring-like spinel, In the granites, the Cr # value is between 45.36 and 49.53, which indicates the subduction environment of the ocean; the pore-like spinel is in the form of disseminated and granular, and the surface has pore development, and the high Cr # value (between 48.39 and 69.90) reflects the island arc environment and indicates the post-collision orogeny; (2) The contents of the main and trace elements of the ring-shaped spinel show that the content of Fe O, Ga, Ni and Ti is increased from the core to the edge, and the content of Al2O3, Mg O, Cr2O3, V, Co and Mn is reduced; and (3) the subduction of the fluid has led to the formation of the spinel belt. The redistribution of elements from the core to the edge. During the fluid metasomatic process, the main components Al2O3 and Mg O in the spinel are transferred, during which the chlorite is filled in the pores, and as the oxidation fluid penetration is further strengthened, The rich Cr2 + and Fe 2 + in the spinel hollow pores can lead to the octahedral coordination of the spinel and the Fe3 + and Fe2 + re-ordering of the tetrahedra, while the elements such as Zn, Co, Mn and Fe 2 + can enter the tetrahedrally coordinated with Mg2 +, while Ni2 +, Ga3 +, elements such as Sc3 + and Ti4 + can enter the octahedral coordination vacated by Al3 +, and the distribution of the regular distribution from the core to the edge leads to the formation of the endless belt; and (4) the fluid plays an important role in the formation of the annular spinel, and the source of the fluid in the ground peridotite is closely related to the construction environment, The study shows that the characteristics of the ground-and-ground olive-rock in the North-East and North-East snake-green hybrid rock are characterized by the loss of the source region, which is the original melting residue, and shows that the mixed-dyeing of the land-source material can be affected by the reduction effect; and (5) according to the characteristics of the spinel belt and the process of the regional construction, The genetic understanding of the spinel belt is as follows: at the stage of the development of the oceanic crust at the stage of 1100 Ma ~ 1000 Ma, the basalt output with the characteristics of the MOB, the spinel in the deep-sea peridotite in the ocean, and the subduction of the Yangtze block with the southern ocean of the ancient China during the period of 1000 Ma ~ 890 Ma, and the partial melting of the geodesic wedge under the island arc. in that period of 890-850 Ma, the oceanic crust further subduction to make the Cathaysian plate and the Yangtze plate collide with the Yangtze plate in the area of Shaoxing-Jiangshan-Meixiang, The tectonic stress produced in the northeast of Jiangxi resulted in the NW-to-fold deformation of the ophiolite in the northeast Jiangxi, resulting in the fracture development of the pore-like spinels, and the large-scale magmatism in the region of the 850-800 Ma phase region, and the influence on the spinel micro-domains is unknown. The spinel has the indication of the origin of the rock, and provides a direct mineralogical proof for exploring the origin of the ophiolite. In this paper, the study of the banded spinels of the middle ring of the ophiolite in the northeast of Jiangxi shows that the formation and evolution of the spinel has a record effect on the formation and evolution of the ophiolite, which can reflect the deep geological process of the rock's experience. In addition, this paper is a preliminary study on the ring-shaped spinels. In the follow-up study, the trace elements, isotopes and fluid sources in the spinel micro-domains can be analyzed and studied, and the distribution rule of the elements in the spinel micro-domains is revealed. Physical and chemical information such as temperature, pressure, oxygen fugacity, etc. when the fluid property and the mineral formation are defined.
【学位授予单位】：东华理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P578.46;P588.1
【参考文献】
相关期刊论文 前1条
1 胡世玲,郝杰,李曰俊;江西德兴西湾钠长花岗岩的激光质谱~(40)Ar/~(39)Ar等时年龄[J];中国区域地质;1998年01期
，本文编号：2510897
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