赣东北大鄣山花岗岩的地质特征、形成时代及其旅游地学意义

为了研究赣东北大鄣山花岗岩的成岩时代及成岩背景,通过LA-ICP-MS锆石U-Pb方法对大鄣山二长花岗岩的形成时代进行了测定,大鄣山二长花岗岩形成于135.0±2.6 Ma B.P.,为早白垩世。花岗岩的主要矿物为钾长石、斜长石、石英等浅色矿物,暗色矿物稀少,有利于抵抗风化侵蚀,保持岩石的完整性。岩石形成于以伸展为主导的构造背景下,张性的节理和断裂更为发育。风化侵蚀作用只能沿节理和断裂逐渐进行,容易形成尖峰、峡谷、断壁悬崖等花岗岩地貌景观。岩石结构和矿物组成是花岗岩地貌景观形成的物质基础;节理和断裂是花岗岩地貌景观的造型控制因素;成岩之后的构造抬升是花岗岩成为景观的必备条件;气候条件、水文条件等也在景观形成过程中扮演着不可或缺的角色。

Chronology,geological characteristics and landscape geological significance of granites from Dazhang Mountain,Jiangxi,China

LA-ICP-MS U-Pb Zircon dating is used to measure the formation age of the monzogranite from the Dazhang Mountain in order to study the age and background of granite diagenesis of the Dazhang Mountain in Northeast Jiangxi.The result constrains the magmatic emplacement at 135.0± 2.6 Ma B.P.(the Early Cretaceous ).The granites are mainly consisted of potash feldspars, plagioclases,quarts and other leucocratic minerals,with a few dark-colored minerals.So,they are more likely to resist weathering and erosion and to preserve integrity.These granites have formed under an extension-dominated tectonic setting and the tensional joints and faults developed well. Weathering and erosion have occured along the joints and faults to create the granite landscapes,such as peaks,valleys and cliffs.The rock structures and mineral compositions provide the material base to form the granite landscape,while the joints and faults control the shapes of the granite landscapes, and the tectonic uplift after diagenesis is the necessary condition to make the granites landscapes. Weather and hydrologic conditions also play an essential part during the process of the landscapes forming.