Geological characteristics of Tianzhu Mountain

Tianzhu Mountain is an integral part of Dabie Mountain extending eastward. The mountain is mainly composed of Wanshan Mountain (commonly known as Tianzhu Mountain in geological circles), which is located at the junction of Yuexi County and Qianshan County in Anhui Province. It spreads in the northwest direction, cutting the public anticline. The exposed area of irregular bedrock on the surface sandwiched by calamus-township head and Shuihouling-Chenlingtou fire faults is 65,438 0.20 square kilometers, and the contact zone with surrounding rocks is mostly covered. The particle size of rock mass near the contact zone becomes finer and the surrounding rock is silicified. Along the contact zone on the east, west and south of the rock mass, we can clearly see the so-called "marginal migmatite" composed of feldspar metasomatism, and its width ranges from tens to hundreds of meters. A small amount of fine amphibole gneiss remains in the rock mass, and baking can be seen at the edge. In Bai Matan area to the west of the rock mass, we can see that there are residual surrounding rock components. Feldspar and syenite veins are developed in the rock mass, which are mainly arranged in northeast oblique lines. Secondly, diorite porphyry and veinlets are also seen.

The facies belt of Wanshan rock mass is asymmetric, and the internal phase is composed of medium-grained mixed granite and mixed adamellite, accounting for more than 90% of the rock mass. Fine-grained rocks often lack tips, usually a few meters to dozens of meters wide. It is wider on both sides of Bai Matan and Sibojian. The historical process of the formation and evolution of Tianzhu Mountain can be traced back to Archaean 2.6 billion years ago. At that time, Tianzhu mountain area, like the whole Dabie mountain area, was in the development period of late Archean marine geosyncline. During the descent of geosyncline, the precursor of Dabie Mountain Group with huge thickness of flysch formation (ultrabasic rocks and basic rocks in the early stage and intermediate-acid volcanic rocks in the late stage) was accumulated in this area.

The Dabie movement at the end of Archean 2 billion years ago caused the marine geosyncline in this area to fold and uplift generally, forming Dingyouling and Xieshan. Due to the regional metamorphism of geosyncline sediments and the orogenic deformation accompanied by the intrusion of granitic magma, Dabie Mountain Group experienced the middle-deep regional metamorphism, forming a mixed granite of migmatization and continental crust transformation, which constituted an isolated metamorphic terrane in this area, namely Huaiyang Uplift, including this area. The Wutai-Lvliang crustal movement (Dabie movement) formed a closed and linear composite fold, and the Yanshan movement occurred in the late period of 65.438+0.40 billion years. Fault activities in NE, NE and N-S directions are generally developed, and the folds are complicated by disturbance and destruction, and they are in the process of uplift and weathering and erosion in different degrees for a long time. Until the late Quaternary (Himalayan period) 2 million years ago, that is, the early Pleistocene, the area rose sharply, reaching more than 1000 meters. River erosion landform is formed in the rising area, especially in the rapidly rising mountainous area. Due to long-term weathering and erosion, the majestic and peculiar natural landscape of Tianzhu Mountain has been formed today.