广西浦北五皇山国家地质公园花岗岩景观特征及其形成演化

Formation and Evolution of the Granite Landscapes in Wuhuangshan National Geopark,Pubei,Guangxi

五皇山地质公园,以浦北岩体为物质基础,是大容山―十万大山花岗岩带和S型花岗岩的典型观测点。园区内发育着石蛋、山岳、台地、峡谷、水文遗迹5大类花岗岩景观,它们有序、集中分布于各个相对独立花岗岩山岳的不同地带,表现出明显的垂直分异特征,共同构成一个以石蛋群为核心,山岳、台地、潭池群和瀑布群为重要补充,形态典型、雄伟、优美、珍稀的南方亚热带花岗岩景观群及石蛋景观群。在分析公园区域地质背景及花岗岩岩体特征的基础上,探讨了公园花岗岩岩体和景观的形成演化过程,认为:1)中三叠世期间,该区域产生了大规模的岩浆活动,历经岩浆侵位、分异、冷凝结晶后,逐渐形成一个时间上连续的、建造上完整的巨型花岗岩岩基——浦北岩体;其后,经历隆升剥蚀出露于地表并成山。2)第四纪至今,受湿热气候、地表流水及原生和后生节理十分发育的花岗岩岩体的共同控制,由山顶→山腰→山脚,它们各自汇聚各种形式地表流水的能力逐渐增强,对应由山顶→山腰→山脚的流水侵蚀程度逐渐增强,而各自的风化作用却逐渐减弱;历经漫长地质历史时期的纵向―横向差异侵蚀、冲蚀和风化作用,逐渐形成公园境内形态典型的南方亚热带花岗岩景观群。

Wuhuangshan Geopark which has been developed in the Pubei pluton is the typical observation point of the Darongshan-Shiwandashan granitoid belt and S-type granite. The granite landscapes in the Geopark are generally classified into five categories： spheroidal stone, mountains, platform, gorge, and hydrological heritage. All of them have been distributed orderly and intensively in the different zones of the granite mountains that are relative independent, and showed obvious vertical differentiation features. These granite landscapes constitute a typical, majestic, beautiful and precious south subtropical granite landscape group and spheroidal stone group with spheroidal stone landscape at the core and mountains, platform, pools group and waterfall group as the important complement. Based on the analysis and investigation about the regional geologic background of the geopark and the characteristics of the granite pluton, this paper systematically studies and discusses the formation and evolution of the granite pluton and the granite landscapes in the geopark. Some main conclusions held by the authors are as follows： 1） During Middle Triassic, there was large-scale magmatic activity in this region, then a giant granite batholith with the continuous time and the integrity of formation, namely, Pubei pluton was gradually formed after a series of processes, i.e. magma emplacement, differentiation, cooling crystallization; and then this pluton was uplifted, denuded and exposed to the earth＇s surface to form mountains. 2） Since Quaternary, controlled jointly by humid-warm climate, surface water and granite pluton in which primary and epigenetic joints developed well, the ability to converge all forms of surface water has been gradually increased from mountaintop→mountainside→foothill, the corresponding erosion has been gradually increased but weathering has been gradually weaken from mountaintop→mountainside→foothill. After going through the process of horizontally-vertically differently erosion, washout and weathering during the long geological period, the typical south subtropical granite landscape group in the geopark has been gradually formed.