地热资源对减少开采利用化石能源，缓解全球环境问题，存在着极大的潜力。在开采利用过程中，地热赋存地层及围岩发生高温水-岩作用，影响地下岩层的稳定性，制约资源的开采效率。因此，研究岩石经过高温水-岩作用后的损伤机制，对提升地热资源的开采利用效率具有重要意义。本文以辉长岩、花岗岩为研究对象，以室内试验为主要手段，结合理论分析方法，研究了高温水-岩作用对两种岩石的影响，通过开展岩石微观结构变化特征和溶液元素变化特征分析试验，揭示岩石溶出矿物元素的变化规律，结合力学试验，阐明岩石发生高温水-岩作用时的变化过程和损伤机制。本文主要取得了以下认识：

（1）经过高温水-岩作用后，辉长岩总孔隙度降低，孔隙结构始终以小孔隙为主；花岗岩孔隙度增加，孔隙结构从以中孔为主过渡到以大孔为主。辉长岩单轴抗压强度提升，在325℃达到最高强度167.77MPa后开始波动变化；花岗岩单轴抗压强度降低，断裂韧度在325℃前从0.92MPa×m^0.5降低至0.50MPa×m^0.5后开始波动变化。随着温度的升高，花岗岩断裂模式从裂纹平行拓展改变为相交发育。辉长岩表面部分区域被溶液中析出的矿物覆盖，辉石颗粒被氧化，少量不规则坑洞出现在样品表面；花岗岩表面在250℃后部分小颗粒长石脱落，长石、石英表面出现较为明显的溶蚀痕迹，325℃后表面角闪石出现氧化痕迹。

（2）基于电感耦合等离子体质谱技术，研究不同温度的高温水-岩作用后，溶液中矿物元素的浓度，揭示处理前后矿物溶蚀元素的变化规律。结果表明，辉长岩、花岗岩溶液内的矿物元素浓度明显增加，按照浓度排序为：Si、Na、K、Ca、Al、Mg，其中Si、Na、Mg的浓度分别为辉长岩：600、16、11.4μg/mL；花岗岩：439、34.2、17.4μg/mL，Si浓度远大于其他元素。元素浓度的变化改变了溶液的物理性质，其中辉长岩pH、电导率随温度的升高整体增加，花岗岩则整体降低。辉长岩各元素浓度在不同温度出现较大的波动，花岗岩波动较小，大部分元素浓度在325℃左右最大。

（3）结合宏-微观变化特征，分析辉长岩、花岗岩高温水-岩作用变化过程，阐述微观结构和矿物成分变化影响力学强度的机制。结果表明，辉长岩、花岗岩受高温水-岩作用的影响分为两个方面，一是矿物的溶蚀，高温水环境下，岩石表面最先出现溶蚀，随着时间的增加，溶液渗入岩石内部，内部矿物开始溶蚀，元素溶出，强度降低。二是矿物受热后体积膨胀，挤压周围的矿物，出现晶间裂隙，当两个晶体相互挤压时，引发热应力集中，加上溶蚀降低了矿物颗粒强度，诱发晶体破裂，岩石强度进一步降低。

Geothermal resources have great potential to reduce the exploitation and utilization of fossil energy and alleviate global environmental problems. In the process of mining and utilization, high temperature water-rock interaction occurs in geothermal strata and surrounding rocks which affects the stability of the underground rock formations and restricts the mining efficiency of resources. Therefore, it is meaningful to study the damage mechanism of rocks after high-temperature water-rock interaction, which is important to improve the utilization efficiency of geothermal resources. In this paper, taking gabbro and granite as the research objects, using laboratory tests as the main means, combined with theoretical analysis methods, the influence of two kinds of rocks under high temperature water-rock interaction was studied. By carrying out analysis tests on the characteristics of changes in rock microstructure and elements in solution, the changing rules of mineral elements dissolved from rock were revealed. Combined with mechanical tests, the change process and damage mechanism of rocks during high-temperature water-rock interaction were clarified. The main conclusions of this paper are as follows.

(1) After high temperature water-rock interaction, the total porosity of the gabbro decreases, but the pore structure is always dominated by small pores. The porosity of granite increases, and the pore structure transitions from dominated by mesopores to dominated by macropores. The uniaxial compressive strength of gabbro increases, and starts to fluctuate after reaching the highest strength of 167.77MPa at 325℃. The uniaxial compressive strength of granite decreases, and the fracture toughness decreased from 0.92MPa×m^0.5 to 0.50MPa×m^0.5 before 325℃, and then starts to fluctuate. With the increase of temperature, the fracture mode of granite changed from crack parallelism expansion changes to intersecting development. Part of the gabbro surface was covered with minerals precipitated from the solution, the pyroxene particles were oxidized, and a small number of irregular pits appeared on the surface of the sample. Some small-grained feldspars fall off on the granite surface after 250°C, and obvious dissolution traces appear on the surfaces of feldspar and quartz, and at 325°C, the hornblende on the rear surface shows oxidation marks.

(2) Based on inductively coupled plasma mass spectrometry, the concentration of some mineral elements in the solution after high temperature water-rock interaction at different temperatures was studied, and the change law of mineral dissolution elements before and after treatment was revealed. The results show that the concentration of mineral elements in the solution of gabbro and granite increases significantly. In order of concentration, they are Si, Na, K, Ca, Al, Mg, of which the concentrations of Si, Na, and Mg are 600, 16, 11.4μg/mL for gabbro; 439, 34.2, 17.4μg/mL for granite, Si is the most important element lost by the two rocks. The change of element concentration changed the physical properties of the solution. The pH and conductivity of gabbro increases with the increase of temperature, while the granite decreases. The element concentration of gabbro fluctuates greatly at different temperatures, while that of granite fluctuates little, and the concentration of most elements reaches its maximum at about 325℃.

(3) Combined with the characteristics of macro and micro changes, the changing process of high-temperature water-rock interaction of gabbro and granite was analyzed, and the mechanism of microstructure and mineral composition changes affecting mechanical strength was expounded. The results show that gabbro and granite are affected by high temperature water-rock interaction in two aspects, one is the dissolution of minerals, under high temperature water environment, the rock surface first appears dissolution, with the increase of time, the solution infiltrates into the rock, the minerals inside the rock begin to dissolve, element water out, the strength decreases. The second is the volume expansion of the mineral heat, squeezing the surrounding minerals, intergranular cracks, when the two crystals squeeze each other, resulting in thermal stress concentration, coupled with dissolution to reduce the strength of mineral particles, the emergence of transgranular cracks, rock strength further reduced.

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