Ore source beds formed by sedimentation, ore source bodies formed by magmatism and ore source bodies formed by hydrothermal process are generally buried deep underground, far away from weathering zones. Especially, the older you get, the deeper the ore source body (layer) is buried. Due to the deformation of tectonic movement, folds and faults in various periods, the ore source bodies (layers) are lifted or lowered, and some ore source bodies (layers) are lifted to the weathering zone for mineralization. This is the result of the change of ore source body under the action of tectonic movement, which creates favorable metallogenic conditions for weathering.

Second, neotectonic movement.

1. Neotectonic movement characteristics

On the basis of the tectonic landscape formed by Yanshan movement, the continental crust of Guangxi has generally uplifted in a large area since Neogene Miocene, forming multi-level planation planes, multi-level river terraces and multi-level karst caves, which have the characteristics of uneven and differential movement in stages, with different ups and downs in different geological periods and different geological units in the same period. According to the research results of Guangxi Hydrogeology Engineering Geology Team 1994, the difference fluctuation mainly has the following characteristics (Table 2- 15).

Table 2- 15 Crustal fluctuation of neotectonic movement in Guangxi

(1) block differential lifting

Due to the uplift of Yunnan-Guizhou Plateau, Guangxi has become a slope belt with high northwest and low southeast. The high slope belt (quasi-plateau) in the west of Beijing is 800m above sea level, and from the east to the left valley 150m, it forms a multi-stage Pitti waterfall, which gradually drops. The drop of Detian waterfall is 40m, the Shuolong tunnel waterfall is more than 20m, and the Shuolong power station is only10 m. The Fulu River in Tian Yang is about 40 kilometers long, with a total length of 20 kilometers from the birthplace of Qiao Ye to the power station. * * There are large and small waterfalls 108, large drop 10m, small drop 1m, more than 70m wide, and more than 70m narrow 10m, of which Tuoshuang Waterfall 15m is about 70m wide.

(2) New and old fault activities

Influenced by neotectonic movement, some old faults are active again. According to the survey data provided by Guangxi Hydropower Design Institute, Bama-Kunlunguan fault was reactivated in early Pleistocene and late Pleistocene (F4). The thermoluminescence dating of No.8 cave in Youjiang dam site is 36 2.3 ~ 46.3 35 thousand years, the age of F4 fault gouge is middle Pleistocene [1], and the age of uranium series method is 32.07 6 ~ 25. It reflects that the Pleistocene activity of the old faults in northwest Guangxi is quite strong.

In recent years, new faults have been discovered, especially in Nanning basin and Baise basin. Quaternary faults have been found in Nanning basin, including Xixiangtang-Weicun fault, Wubeiling fault, Xianshengling fault and Dongpo fault of Baise basin oilfield. The general length is 50m 25km, and the fault distance is 3 16m. Mostly normal faults.

According to the research of Guangxi Hydrogeology Engineering Geology Team 1994, there are 13 main active faults in Guangxi, and their comprehensive characteristics are shown in Table 2- 16.

Table 2- 16 Characteristics of Active Faults in Guangxi

sequential

(3) Earthquake

According to the earthquake chronology of Guangxi, there have been 266 earthquakes in Guangxi since 288 1996, of which 13 were destructive earthquakes. Earthquakes with magnitude above 4 are mainly distributed in Cenxi-Bobai, Lingshan-tengxian in the northeast, Youjiang, Napo and Danchi in the northwest.

2. The result of neotectonic movement

(1) Based on the landscape of ancient structures (Yanshan period and its previous structures), the landform fluctuates, resulting in different weathering and erosion differences, thus creating the present landform landscape.

(2) Buried underground ore source bodies (layers) are lifted into the weathering zone to promote mineralization or destroy weathered deposits (the formed weathered deposits are denuded).