發(fā)布時間：2018-12-18 16:03

【摘要】：火山噴發(fā)必然伴隨著高溫巖漿侵入體把熱量從巖石圈深部攜帶到地殼淺層的過程,因而火山區(qū)往往也是地熱資源富集區(qū)�；鹕綆r漿侵入體熱擴散過程的數(shù)值模擬不僅是火山區(qū)構造熱演化研究的重要手段,而且也是火山區(qū)地熱資源評估的重要方法。本文利用在工程熱物理領域應用甚廣、但在地熱地球物理領域鮮有報道的有限元軟件ANSYS WORKBENCH對火山活動巖漿冷卻過程及其對圍巖的熱擾動過程進行了數(shù)值模擬。首先本文建立一系列簡單的柱狀模型,模擬了不同規(guī)模、不同頂板埋深的侵入體的熱擴散過程,引入冷卻指數(shù)α=(T_(侵入)-T)/(T_(侵入)-T_(穩(wěn)態(tài)))×100%及干擾溫差ΔT=T-T穩(wěn)態(tài)分別來定量分析巖漿侵入體冷卻過程及圍巖受侵入體熱擴散擾動程度。結果表明,半徑為0.5km的柱狀侵入體的冷卻時間約為50ka左右,對圍巖熱擾動持續(xù)時間不到0.5Ma,最大橫向熱擾動范圍約為3km。而半徑1km的柱狀侵入體的冷卻時間約為200ka左右,對圍巖溫度場影響可持續(xù)1.4Ma,熱擾動范圍可至7km。頂板埋深越大,侵入體對圍巖熱擾動的持續(xù)時間越短。在上述模擬實驗的基礎上,本文結合最新的相關研究成果,模擬計算了上地殼巖漿房和上中地殼巖漿房兩種情景下長白山天池火山千年大噴發(fā)對于溫度場的可能影響。結果表明,無論其巖漿房位于上地殼或中地殼上部,千年大噴發(fā)對于圍巖的熱擾動目前還局限于500m左右的范圍內(nèi),這可能是區(qū)內(nèi)尚無大規(guī)模地熱顯示的原因。
[Abstract]:Volcanic eruptions must be accompanied by high temperature magmatic intrusions to carry heat from the deep lithosphere to the shallow crust. Therefore, thermal mountain areas are often rich in geothermal resources. Numerical simulation of thermal diffusion process of volcanic magma intrusive body is not only an important means to study the thermal evolution of thermal structure in the volcanic mountain area, but also an important method to evaluate geothermal resources in the volcanic area. In this paper the cooling process of volcanic magma and the thermal disturbance of surrounding rock are numerically simulated by using finite element software ANSYS WORKBENCH which is widely used in engineering thermal physics but rarely reported in geothermal geophysics. First of all, a series of simple cylindrical models are established to simulate the thermal diffusion process of intrusions with different sizes and different roof depths. The cooling index 偽 = (T _ (intrusive) -T) / (T _ (intrusive) -T _ (steady) 脳 100% and disturbance temperature difference 螖 T=T-T steady state are introduced to quantitatively analyze the cooling process of magmatic intrusions and the disturbance degree of surrounding rock by thermal diffusion of intrusive body. The results show that the cooling time of cylindrical intrusions with radius of 0.5km is about 50ka, the thermal disturbance duration of surrounding rock is less than 0.5 Ma, and the maximum transverse thermal disturbance range is about 3 km. The cooling time of the columnar intrusions with radius 1km is about 200ka, and the influence on the temperature field of surrounding rock is 1.4 Ma, and the thermal disturbance range is up to 7 km. The deeper the roof is, the shorter the duration of thermal disturbance of surrounding rock is. On the basis of the above simulation experiments, the possible effects of the millennium eruption of Tianchi volcano in Changbai Mountain on the temperature field under the two scenarios of the upper crust magma chamber and the upper middle crust magma chamber are simulated and calculated in combination with the latest relevant research results. The results show that, no matter the magma chamber is located in the upper crust or the upper middle crust, the thermal disturbance caused by the millennium eruption to the surrounding rock is still limited to about 500 m, which may be the reason that there is no large-scale geothermal display in the area.
【作者單位】： 西安交通大學全球環(huán)境變化研究院地熱與環(huán)境研究實驗室;美國密歇根大學地球與環(huán)境科學系;
【基金】：國家自然科學基金項目(41374089)資助
【分類號】：P588.14

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