Yunnan Mine Tour (Midu Ma Changqing Gold Mine-1)

Speaking of Yunnan gold mines, those familiar names always come to my mind, but apart from fame, the original landforms of many Yunnan gold mines have been gradually replaced by commercial interests of mining, so they can't be my favorite destinations. During a short driving trip on Valentine's Day and Lantern Festival on 20 19, I found the Ma Changqing Gold Mine, which is not too far from hongyan town, Midu County.

The first time I met Ma Changqing Gold Mine, it originated from a chat after dinner. According to friends, there is also a little-known gold mine in hongyan town, Midu, Dali, which retains part of its original ecology. I'm fascinated and want to find out. However, due to the busy life, 20 18 has not been able to make it. On the fifteenth day of the first month of the Spring Festival, I traveled at the wrong peak, and finally I was able to drive to the Ma Changqing Gold Mine in hongyan town, Midu County, which made many people feel a lot.

The road from Kunming to Dali has gone through countless times. Although the wind in early spring is still mixed with a hint of coolness, the blue sky and white clouds are refreshing against the green mountains and green waters on the roadside. The hardships on the road didn't affect my mood at all, and it was near dusk when I arrived in hongyan town, Midu County. Under the faint oblique light, my first impression of hongyan town is not cold and bleak, but fresh and quiet.

As a small town, hongyan town is not as crowded as other towns I have been to before, even though the day I arrived coincided with the Lantern Festival. Walking on the concrete road of hongyan town Street at night, looking at few figures and messy shops, it is hard for me to remember the scene of the bustling crowd during the day.

Hongyan town is located in the northwest of Midu Dam, surrounded by mountains on three sides, with Michuan in the south, Dali in the north, Xiangyun in the east and Weishan in the west. Jiuding Mountain in China is the highest peak in Midu, with an altitude of 3 1 17.9 meters. The elevation of the dam area is1720m, and the terrain is high in the north and low in the south. Chishui River in the east and Shao Qing and Wangjiaqing at Qiaotou in the west flow into Pixiong River. Hongyan town is located in the northernmost part of Midu County, and the Chu-Da Expressway (Dali-Chuxiong section of G56 Hangrui Expressway), National Highway 2 14, Guohe Highway and Midu West Road pass through the territory, with convenient transportation and pleasant climate. North Gate of Midu County, which is separated from Dali, the resident of Dali Bai Autonomous Prefecture, by a mountain.

Hongyan town is so quiet after dark. I've been in a noisy big city for a long time, and I don't seem to be used to it. When the weather is fine, you can see the stars all over the sky, which also makes many donkey friends take pictures of the villages and towns, while I go back to the inn and choose to enjoy scented tea in the humble hall, but I can't seem to get rid of the vulgarity and completely escape the bondage of the internet. After walking for a long time, there are already some pictures in the mobile phone WeChat that can be shown off to friends. Looking at their praise, I told myself that the nature of pursuing simplicity has not changed. More often, people get drunk in noisy bars, which is actually a kind of self-paralysis, just because they are not quiet enough to really get out.

Breathing fresh air, I spent my first quiet night in hongyan town without any interruption. The next day, with the sunrise, the bell rang when I visited the Ma Changqing Gold Mine in hongyan town, Midu. After a simple breakfast in the inn, I drove and crawled on the mountain road with my luggage.

Ma Changqing Gold Mine is located at the junction of Dali, Midu and Xiangyun counties, and its administrative division is under the jurisdiction of Midu County, Dali Prefecture. It is located on the east side of the junction of Yangtze landmass and Changdu-Simao landmass, and on the southwest edge of Lijiang platform marginal fold belt on the southwest edge of Yangtze landmass. It is a typical deposit related to alkali-rich intrusive rocks in Jinshajiang-Ailaoshan structural belt. Ma Changqing Gold Mine is a polymetallic mine with copper, molybdenum and gold as the main minerals, and its proven gold reserves have reached a large scale.

The light in the morning is warm and soft. You can see Ma Changqing Village by driving to auspicious village and walking a mountain road to the north. At this time, an old man was driving a group of black goats to walk leisurely on the gravel-covered hillside road, which made me envy his mentality of not chasing or catching up. Even goats that eat leaves on the slope seem to be not afraid of passers-by. The mine and clear stream in front of us set off a good picture with Jiuding Mountain in the distance. Ma Changqing Village also produces Chinese herbal medicine-seven leaves and one flower.

After arriving at Ma Changqing Village, I continued to walk along the path to Jiuding Mountain for an hour, and then I saw the gold mineralization belt.

The gold mineralization belt in Ma Changqing is generally distributed in the northeast direction. Dozens of mineralized bodies (veins) such as copper, molybdenum, gold, iron, lead and zinc have been found in the mineralized zone with a length of 12km and a width of 2.5km, which are divided into Ma Changqing, Rentouqing, Luandongshan, Baoxingchang and Xinshan from northeast to southwest.

The occurrence of ore bodies (veins) in Ma Changqing Gold Mine is closely related to alkali-rich rock bodies (veins) in the area, and the alteration zoning is obvious in space, time or later. The study of gold abundance, isotopes and rare earth elements in ore deposits and related alkali-rich rocks (veins) shows that alkali-rich rocks themselves are not the source of minerals. Ore-forming fluids and main minerals come from the deep part of the earth, mainly in the upper mantle or the mixed zone of crust and mantle.

Tired of walking, I sat down on a flat stone, drank saliva, took out mine geological data from my bag and looked at the geological situation of the gold mine.

The tectonic position of the mining area is located at the junction of the western margin of Yangtze plate and Lanping-Simao microplate. The northwest Jinsha River-Ailaoshan suture zone and the northeast Chenghai-Binchuan fault respectively pass through the southwest and east of the mining area and meet in the south of the mining area, so the deposit occurs in the triangle surrounded by these two deep faults. In the alkali-rich rock belt in northwest Yunnan, it belongs to the Dali-Yi Yun (including Binchuan) rock mass (vein) intensive area in the southern rock belt.

The strata exposed in the mining area are mainly the 3rd and 4th members of Xiangyang Formation of Lower Ordovician, Kanglang Formation of Lower Devonian and Qingshan Formation (Figure 1).

Among them, the fourth member of the Lower Ordovician is the main distribution stratum in the mining area, which is divided into two sub-sections: the lower sub-section is gray coarse-grained feldspar sandstone with conglomerate, gravelly coarse sandstone and gray-green siltstone; The middle and lower part of the upper sub-member is purplish red, dark gray and thin to thick layered timely feldspar siltstone, black carbon argillaceous fine sandstone mixed with limestone and argillaceous dolomite lens, and the upper part is interbedded with gray thin limestone and thin siltstone. This submember is widely distributed in the mining area and is the main ore-bearing stratum.

The structure of the mining area is mainly controlled by regional NW-trending, N-S-trending main faults and nearly EW-trending concealed structures. There are faults and folds of different types and scales in NE-trending, EW-trending, NW-trending and N-S-trending, and the structural activities have obvious multi-stage and multi-stage characteristics. According to the relationship between structure and gold mineralization, it can be divided into several tectonic active periods: basic tectonic period, metallogenic tectonic period and post-metallogenic tectonic period. The basic structures are mainly folds and faults in ne direction, NE direction or near EW direction, and the representative structures are F 1 fault (NE direction), Jinchangqing anticline (NE direction), Luandongshan-Tongchang syncline (EW direction) and so on. The research shows that these structures are important rock-controlling structures in this area, which control the location and distribution of alkali-rich rocks (veins) in the early mining area and are closely related to copper-molybdenum mineralization in this area. Metallogenic structure mainly refers to the metallogenic structure of gold deposits, which can be divided into two fault groups:

1, N-S fault group, mainly including Tongchang F30, Malipo F3 1 and ShishHuang Qing F32；;

2. Near east-west fault groups, mainly including F, F5, F6, F34, F3 and F36. These two groups of structures are a pair of yoke faults. Together with the early pleated beryllium structure, they not only controlled the distribution of alkali-rich rocks (veins) in the later period, but also jointly controlled the distribution of gold veins. After mineralization, the structure is not very developed, mainly northeast, and the scale is generally small.

Alkali-rich rocks (veins) mainly consisting of monzoporphyry, granite porphyry, syenite porphyry and lamprophyre are widely exposed in the mining area and its periphery, and there are Hercynian gabbro veins in the area.

Alkali-rich magmatism has obvious multi-stage and multi-stage characteristics, and Ma Changqing complex is its typical representative. The complex is exposed in the west of the mining area and consists of more than 260 kinds of rocks, mainly syenite porphyry and granite porphyry, with rock clusters, dikes, bedrock, dikes or pillars. According to the interpenetration between dikes, the sequence of magmatic activity can be divided into three stages:

① Early intrusive stage dominated by porphyry granite-granite porphyry;

(2) Middle intrusive stage dominated by shallow alkali feldspar granite;

③ In the late intrusive stage, syenite porphyry-adamellite porphyry-granite porphyry is dominant.

The petrochemical composition of each stage has certain regular changes. Early magmatic activity was restricted by the intersection of NE and NW structures, and was closely related to copper (molybdenum) mineralization. In the middle and late stage, it was mainly controlled by the near east-west structure, forming a series of near east-west dikes, which were closely related to gold mineralization in Jinchangqing and Baoxingchang areas.