胶东半岛不同构造单元深部热流分流聚热模式

中生代、新生代时期地壳剧烈运动将胶东半岛划分为胶北隆起、胶莱凹陷、胶南-威海隆起三大构造单元,其中隆起山地区广泛分布花岗岩、变质岩,凹陷盆地区主要分布砂岩沉积地层,胶北隆起区与威海隆起区相对于胶莱凹陷盆地区具有更高的大地热流值.为系统分析胶东半岛大地热流值分布特征及其形成机理,本文在分析胶东半岛构造-热发展史、地热地质背景、地温场分布、岩石热导率、钻孔岩性与测温数据、地热流体化学成分等基础上,发现胶东半岛地热资源均为断裂构造控制类型的中低温对流型,其热源主要为三元聚热:导热断裂带水热对流、大地热流传导、地下水运移传导-对流;构造分布、岩石热物性、地热热储分布、地下水活动等是影响地温场分布的主要因素.针对胶东半岛地温场特征及其控制因素,提出了适合该地区的隆起-凹陷分流聚热模式与概念模型,即隆起山地区岩性以导热率、渗透率相对较高的侵入岩、变质岩为主,凹陷盆地区岩性以导热率、渗透率相对较低的砂岩为主,低导热率、低渗透率的凹陷区底部更像是一个相对隔热、隔水的顶板,使得来自地壳深部的大地热流及携带热量的流体、气体等在上涌的过程中在凹陷区的底部发生折射与再分配,从而导致热流在隆起山地区的底部形成一个温度相对更高的聚热区,反映在地表即是隆起山地区相对凹陷盆地区具有更高的大地热流值,特别隆起山地区轴部位置为热流值最高的区域,高热流值区域分布形态呈NE、NNE向分布,基本与胶东半岛NE、NNE向的深大断裂走向一致,该模式的提出可以更好地为胶东地区的地热资源勘探提供指导方向.

Discussion on the deep heat flow diversion- acculturation between uplift and depression in different tectonic units in the Jiaodong Peninsula

The strenuous movement of the crust in the Mesozoic and Cenozoic periods divided the Jiaodong Peninsula into three major tectonic units: Jiaobei uplift, Jiaolai depression, and Jiaonan- Weihai uplift. The uplift area is widely covered with granite and metamorphic rocks, and the depression area mainly composedof sedimentary sandstone. The Jiaobei uplift area and the Weihai uplift area have higher heat flow values than the Jiaolai depression area. In order to systematically analyze the distribution characteristics and mechanism of heat flow in the Jiaodong Peninsula, this paper analyzes the tectonic- thermal development history, geothermal geological background, geothermal field distribution, rock thermal conductivity, borehole lithology and temperature data, chemical composition of geothermal fluid etc. in the Jiaodong Peninsula. We find that the geothermal resources in the Jiaodong Peninsula are all medium- low temperature convective geothermal resources of fault control type. Its heat sources mainly come from hydrothermal convection in fault zones, terrestrial heat flow and conduction- convection in groundwater transport. Fault distribution, thermal properties of rocks, geothermal reservoir distribution, groundwater activities, etc. are the main factors affecting the distribution of thermal field. A conceptual model of heat flow diversion- acculturation between uplift and depression in the Jiaodong peninsula is proposed using the thermal field characteristics and its controlling factors. The lithology of the uplift area is mainly composed of intrusive rocks and metamorphic rocks with high thermal conductivity. The lithology of the depression basin is mainly composed of sandstone with low thermal conductivity. The bottom of the depression with low thermal conductivity and low permeability is more like a heat insulation and water insulation roof, which causes the heat flow or the heat- carrying fluids and gases from the deep crust to be refracted and redistributed at the bottom of the depression area. As a result, the bottom of the uplift areas has higher heat flow and the highest heat flow is in the axial position of uplift area. The distribution pattern of high heat flow value is almost the same to the faults strike to NE and NNE direction. This model can better provide exploration direction for geothermal resource exploration in the Jiaodong area.