First, the uniqueness of multiple configurations of geological structures in the shallow crust.
1) Each structural layer (including some lithostratigraphic units) is mainly located in the west of the Strait, with a small extension and poor continuity. Therefore, in many areas, under different underground depths, pressures and temperatures, it is a structural layer with a small exposed area, almost at the surface level. For example, it is inferred that the Paleoproterozoic Wuyi structural layer formed underground 10km at a temperature of 500 ~ 600℃ is often the same as the Caledonian, Hercynian, Indosinian, Yanshan and Himalayan structural layers formed on the crust surface, and the structural environment formed between them is very different, which mainly reflects that the subsequent structural layers broke (rift valley, rift valley and Himalayan period) during the formation of strata. Yongmei sag had a great uplift and denudation after Wuyi Movement and before Sinian, and was relatively stable in northwest Fujian after Mesoproterozoic, but slightly uplifted or lowered. The so-called skylight in Ninghua New Village, Wuping Taoxi, Yongding Rentian, Xingning Chengguan, Anxi Jiandou, Dehua Upwelling, Youxi Banmian, Meixian, Yongtai Changqing, Pingnan Pandi and other places is caused by several different types of block movements and has different characteristics of later activities. The ore-bearing strata (groups) inherent in these ancient fault blocks and the deep faults around them have become favorable factors for the superimposed mineralization of ore-bearing strata (groups) and Yanshanian period, which can be explored and evaluated by modern technology.
2) Many different provenances and sources of magma and new and old rock masses controlled by structures are exposed on the surface, and most of the structural layers have been strongly reformed in three dimensions, so that geological bodies (including structural layers) with a certain depth between the surface and the underground have been cut many times. The linear distribution of four NE-trending intrusive rock belts is superimposed with two NW-trending and NE-trending intrusive rock belts, and it is combined with the rock mass in southwest Fujian in the form of core (Xiaotao rock mass) arc (Hufang-Weipu-Xuanhe rock mass) (also called ear-shaped rock mass), which not only shows large (giant) linear (mainly fracture) concealed structural deformation belts, but also marks Mesoproterozoic and Silurian. In the above-mentioned multi-source and multi-element rock mass zones or nodes, mineralization often occurs in shallow denuded rock mass or unit concealed rock mass (unit) and surrounding rock, depending on the migration energy of ore-forming elements, high (titanium), medium (tungsten, tin) and low (gold, silver, copper). There are still concealed rock masses and geochemical anomalies shown by geophysics and geochemistry in the structural magmatic belts from Ninghua to Jiangle, Longyan to Zhangping and Dehua to Yongtai in this area, which deserves attention.
Secondly, fault is the most important and common structural form.
It develops in two main structural types of layered geological bodies, namely folds and fractures, especially in layered strata covering crystalline basement strata. Although folds are common, fractures are the most important and common structural form. The well-preserved Mingxi-Liancheng-Meizhou and Datian-Longyan composite anticlines in Hercynian and Indosinian periods, according to the existence of Laiyuan (Liancheng)-Shuangjishan (Shanghang) uplift belt in the paleogeographic pattern of Yongmei tongue-shaped land surface, resulted in thick sediment accumulation in the trough rift under the tension background. Extensional faults (rifts) of Carboniferous and Early Triassic syngenetic deposits in northeast China (Liancheng Tian Xin, Shanghang Huyang, Yongding Cheng Bang, Meizhou Yushui, Datian Longfengchang-Shangcai, Datian Xiong Feng-Wenhua, Dehua Yangshan-Jiandu, Longyan Makeng, Longyan Houtian, Hua 'an Caoban, etc.). ) and Luoyang in the northeast (Zhangping). This phenomenon was also true during the period of Da 'nan 'ao in Taiwan Province Province. The "well" rift in Mesoproterozoic also has a "four in one" situation similar to Hercynian and Indosinian.
In the three sub-periods of Yanshan Ivory Stage, Nanyuan Stage and Shimaoshan Stage, almost all regional major faults dominated various geological processes, including regional faults, magmatic eruption (deposition), volcanic subsidence, mineralization, regional fault revival, magmatic intrusion, local faults and mineralization. Each sub-stage has the characteristics of "four in one" geological evolution, and the Himalayan period also has the characteristics of geological evolution similar to the Yanshan period in the coastal mountainous areas and Jinguashi areas east of Taitung longitudinal valley.
Three. The main geological processes and mineralization in the restricted area of regional large-scale fault with beam lattice.
Jiangshan-Shaoxing, Zhenghe-Anxi faults formed in Mesoproterozoic and Wenzhou-Shantou faults possibly formed in this period meet in Ningbo area, forming the early fault pattern and bundle faults in this area. Indosinian Movement (some may be earlier) and Yanshan Movement (including Three Scenes) inherited and reborn the Northeast (Chong 'an-Shicheng, Guangze-Wuping, Zhenghe-Dapu, Shouning-Hua 'an, Fuan-Nanjing, Wenshan, Chen Da-Wuqiu (and possibly Quchi-Chaozhou) and Northeast-Dongguangze-Jiumu and Ningning. Shanghang-Xiao Yun fault and Shan-Xingning fault are mostly active for many times, controlling sedimentation, magma and mineralization. They are mainly brittle fractures, followed by ductile and brittle-ductile fractures, and the width of the fault zone is relatively large. These faults are often tectonic magmatic belts, and Yanshanian magmatic activities are mainly controlled by them. In the lattice space of large fault zone, there are often dense checkerboard structures of joint faults.
Nanping, located at the northeast end of Yongmei depression belt, is another noteworthy cluster fault gathering place in this area. Nanping-Ninghua fault and Zhenghe-Dapu fault converge in Nanping, other faults and folds also converge in Nanping, and the arc of intrusive rock mass also protrudes in Nanping, indicating that the stress in the right strike-slip area accumulates in Nanping direction. Therefore, many geological processes in Liu Qing, Jiangle, Shunchang, Nanping and Datian are different from mineralization and deep geological processes.
4. Major regional faults have obvious multi-element geochemical anomaly zones.
The Zhenghe-Dabu fault zone in this area and the Jiangshan-Shaoxing fault zone in the north of this area have the same zonal geochemical anomalies of oxygen-loving elements such as chromium, nickel, cobalt and copper and sulfur elements. From Lishui-Zhenqian (Zhenghe)-Gutian and Youxi-Huaan-Dabu, a negative anomaly zone with clear western boundary and fuzzy eastern boundary is formed, which is quite noticeable in regional geochemistry. In the west of the negative anomaly zone, Guangze-Heyuan and Zhouling (Jian 'ou)-Xingning form two basically continuous geochemical anomaly zones, in which the positive anomalies of potassium, zirconium, lanthanum and vanadium are nested with the negative anomalies of copper, cobalt, nickel, chromium and vanadium, which are large hidden fault zones and control the distribution of regional heavy lava bodies.
In the northwest of Shanghang-Xiao Yun fault zone, there are negative anomaly zones of chromium, nickel, cobalt, vanadium and copper and positive anomaly zones of potassium, sodium, strontium, barium and aluminum. The spatial location of this belt is in Raoping, the southeast end, which generally reflects the characteristics of the rock mass belt formed along the Shanghang-Xiao Yun fault zone.
5. Vertical upward movement is extremely important among multiple structural factors, and it is extremely important to integrate the vertical movement of different material forms restricted by multiple structural factors.
Since Proterozoic, this area has experienced 1 1 geological periods such as Mesoproterozoic, Neoproterozoic, Sinian, Silurian, Carboniferous, Triassic, Early Jurassic, Late Jurassic, Cretaceous and Tertiary, during which the asthenosphere and upper mantle fractures melted, the lower and middle crust remelted, the upper crust mixed and the upper crust cracked. Each time, they intermittently vertically move different forms of upper mantle materials (such as silicate molten slurry and slurry, gas-liquid fluid and heat energy, etc.) in different spaces in the crust in various forms (eruption, intrusion, mantle plume, etc.). ) or escape into the atmosphere.
Similarly, the paleocrust in the middle and upper crust is mainly influenced by the thermal energy and chemical energy generated by the upper mantle cutting, crust rupture and mantle remelting. The derivatives of the crust and the initial substances of the mantle are located in different three-dimensional spaces in the crust from bottom to top in different material forms (silicate melt, mineral magma, gas-liquid fluid, etc.). ) Through folds (bedding) in the middle and lower crust, magmatic eruption, intrusion and quasi-in-situ mixing. At present, magmatic rocks with different distribution trends, such as linear, trough-shaped, porphyry, chain-shaped, banded, magmatic rocks containing natural gold in Shanghang and Heping Lake, hydrothermal altered rocks (so-called amphibole in Xikou Formation), endogenetic ore bodies, Huyang (pyrite layer of Yushui copper mine) veins, mixed granite, etc. They are all affected by comprehensive geological structural factors (uplift and fold of B' and B "layers in the upper mantle, imbalance of overheated high conductivity layers in the crust during fracture, disintegration of radioactive elements, escape of gas and liquid in the crust and mantle, mechanical energy of crust and mantle fracture, etc.). ), and they move vertically from deep to shallow, even to the surface. This vertical material movement and its various material construction records are the most prominent features in the geological structure and lithosphere in this area. The deep circulation hydrothermal solution and fault mineralization since Quaternary are typical examples to understand this geological structure phenomenon.