黑龙江省东安—汤旺河地区花岗岩地球化学及热年代学

发布时间：2018-03-05 06:08

本文选题：黑龙江省　切入点：东安-汤旺河地区　出处：《中国地质大学(北京)》2015年硕士论文　论文类型：学位论文

【摘要】：东安-汤旺河地区位于小兴安岭北缘,松嫩地块与佳木斯地块的衔接地带。本文对位于该研究区的东安金矿区、平顶山金矿区、翠宏山多金属矿区分布的典型花岗岩体进行了岩石学、锆石U-Pb年代学、元素地球化学研究,探讨了岩体的成因及形成的大地构造背景;通过锆石、磷灰石裂变径迹热年代学结合其他同位素年龄研究了岩体自侵位以来的热史演化过程,结合地温梯度计算了岩体在不同阶段的冷却速率、隆升速率和区域剥蚀量,并进一步探讨了造成岩体不均一的抬升剥蚀阶段的地质构造背景。岩石地球化学研究显示,平顶山岩体形成于晚古生代(259±1Ma),高钾钙碱性系列弱过铝质的相对富钙、贫铁、镁,由I型向A型过渡型花岗岩,源区物质来自下地壳物质的部分熔融,形成于华北板块与西伯利亚板块碰撞拼贴过程中伴随的陆内块体间的碰撞机制下;翠宏山岩体形成于晚三叠世(200±1Ma),为高钾钙碱性系列准铝质-弱过铝质过渡的贫钙、铁、镁的A型花岗岩,源区物质表现为壳幔混合型,以壳源为主,形成于华北板块与西伯利亚板块碰撞造山古亚洲洋最终闭合后的伸展机制下;东安岩体形成于早侏罗世(188±1Ma),为高钾钙碱性系列弱过铝质的贫钙、铁、镁岩,为形成于早侏罗世古太平洋板块持续俯冲机制下的以地壳物质为主,部分幔源物质加入的A型中粗粒碱长花岗岩。因三类花岗岩AFT与ZFT值远远小于岩体的形成年龄,磷灰石裂变径迹长度分布均表现出近矮而宽的单峰分布,且径迹长度远小于裂变径迹的标准初始径迹长度16.3um,样品的单颗粒年龄值相对分散,说明磷灰石在漫长的地质历史过程中经历的较为缓慢的冷却退火过程。翠宏山岩体AFT大于平顶山岩体,平顶山岩体AFT大于东安岩体,这种裂变径迹年龄的差异反应了研究区不均匀的构造抬升格局,表明翠宏山岩体晚中生代以来较早经历抬升剥蚀,平顶山岩体较晚抬升至磷灰石裂变径迹退火带底部温度等温面。样品的AFT值与样品所在高度之间反映出明显的正相关性,说明随着岩体隆升与冷却作用的进行,较高处样品相对较早的抬升到裂变径迹部分退火带底部;岩体样品的部分磷灰石裂变径迹年龄值与样品所在高度之间不具有正相关性,可能是岩体在抬升通过110±10°C的等温面深度后局部遭受小规模构造运动的影响,使该区岩体发生局部性的逆冲推覆等情况。通过磷灰石裂变径迹热历史模拟,结合锆石裂变径迹年龄、黑云母K-Ar年龄及锆石U-Pb年龄,表明岩体自侵位以来经历了不均匀的冷却降温过程;由样品在不同阶段的冷却速率、隆升速率及隆升量,总体表现为3个阶段的不均一的抬升及剥蚀;根据现代大陆平均剥蚀速率获得研究区自早侏罗世以来区域剥蚀深度在6.5Km左右;3个阶段不均一的抬升剥蚀过程很可能是由于古太平洋板块持续俯冲伴随的软流圈地幔物质底侵上涌以及陆内造山运动综合作用的结果。
[Abstract]:Dongan area is located in the northern margin of Xingan mountains Tangwanghe, zone between Songnen massif and Jiamusi massif. The study area is located in the Dongan gold mine, Pingdingshan gold mining area, the typical granite Distribution cuihongshan polymetallic mining area of petrography, U-Pb zircon geochronology, geochemistry of rock mass is discussed, and the causes of the tectonic background; the zircon and apatite fission track thermal history of rock mass from emplacement since in combination with other isotopic age evolution of rock mass in the same stage of the cooling rate was calculated with the temperature gradient, the uplift rate and regional denudation, and further discusses the geological background caused by the inhomogeneity of rock mass the uplift and denudation stage. Geochemical study shows that the Pingdingshan rock formed in the late Paleozoic (259 + 1Ma), high potassium calc alkaline series weak peraluminous Relatively rich in calcium, magnesium, iron poor, from I type to A type transition type granite, partial melting of source material from the lower crust, formed in the North China plate and the Siberia plate collision collage process with the intracontinent block collision mechanism; cuihongshan rock formed in Late Triassic three (200 + 1Ma), high potassium calc alkaline series metaluminous had poor calcium, aluminum transition iron, magnesium A type granite, source material for crust mantle mixed type, derived mainly from the crust, formed in the extensional mechanism of the North China plate and the Siberia plate collision after the final closure of the paleo Asian Ocean Dongan; rock formed in the early Jurassic (188 + 1Ma), high potassium calc alkaline series weak poor calcium aluminum, iron, magnesium and rock, was formed in the early Jurassic paleo Pacific plate subduction mechanism under the crust, coarse grained alkali type A part of the mantle material into the granite because of the three. Type of granite AFT and ZFT value is far less than the formation age of rock mass, apatite fission track length distribution showed in short and wide unimodal distribution, the standard initial track length 16.3um and track length is far less than the fission track age, single particle sample value is relatively dispersed, that experience in the geological history of apatite in the process of long time is slow cooling annealing process. The cuihongshan rock rock rock AFT is greater than Pingdingshan, Pingdingshan, Dongan more than AFT rock mass, the difference of fission track age reaction in the study area the uneven pattern of tectonic uplift, the Cuihong mountain rock uplift since Late Mesozoic early experience, Pingdingshan rock later uplifted to the apatite fission track annealing with the bottom temperature the isothermal surface between the sample AFT value. The samples and the height reflects a significant positive correlation, with rock uplift and cooling effect The sample is high, relatively early uplift to the fission track annealing zone at the bottom part of the rock sample; part of the apatite fission track age value and the height between the sample does not have positive correlation, may be the isotherm depth of rock mass in uplift by 110 + 10 ~ C after the Bureau of the Ministry of small scale affected by tectonic movement, the the local rock mass of thrust nappe and so on. Through the apatite fission track thermal history simulation, combined with the zircon fission track age, biotite and K-Ar ages of zircon U-Pb age, shows that the rock mass self emplacement has experienced uneven cooling process; the cooling rate of samples in different stages, the uplift rate the uplift amount, the overall performance of uplift and denudation of the 3 phases are not uniform; according to the average erosion rate of modern China to get the study area since the early Jurassic since the regional denudation depth of around 6.5Km; 3 The process of uplift and denudation at different stages is probably due to the combined effect of continuous subduction of the paleo Pacific plate and asthenospheric mantle invasion and upwelling.

【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P588.121;P597.3

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