Shulou(Shulou.com)11/24 Report--

This article comes from the official account of Wechat: Earth knowledge Bureau (ID:diqiuzhishiju), author: cold

The original title: "just now, China has discovered a world-class gold mine!" "

Recently, a giant single gold deposit has been discovered in Shandong Province, China, which is located in Xiling Village, Laizhou City, Shandong Province. According to the preliminary determination of the Provincial Department of Natural Resources, the amount of newly added gold metal in Xiling Gold Mine is nearly 200 tons, with a cumulative gold metal amount of 580 tons, with a potential economic value of more than 200 billion yuan. Xiling gold deposit is the largest single gold deposit discovered in China so far, and it is a world-class giant single gold deposit.

This discovery is a major achievement of the strategic action of ore prospecting breakthrough in China. Because gold has been flashing its unique economic value since ancient times, but China is a country seriously short of gold.

Since 1971, the price of dollar gold has risen 43-fold, largely outperforming global inflation and most commodities and other metals. Especially in recent years, the global economy has been affected by the impact of the epidemic, currency overissuance, anti-globalization and geopolitical upheaval, and gold has become an excellent safe haven investment. The important role of gold in the modern economy is incomparable.

At a time when the economic situation is uncertain

Gold can give us enough sense of security ▼.

Such an important gold, its upstream gold mineral is also a very important industry.

On the evening of October 18, 2021, Zijin Mining announced its intention to acquire the world-class large-scale production Rosebel gold project in Suriname held by Canada's IAMGOLD Gold Mining Company for US $360 million.

On November 6, Zijin Mining became the second largest shareholder of Zhaojin Mining. Two domestic head gold companies joined forces and made a number of overseas gold acquisitions.

The Rosebel gold deposit is one of the largest gold deposits in South America.

The acquisition of gold mines has effectively ensured the supply of gold in our country.

(figure: rosebelgoldmines.sr) ▼

Domestic enterprises have invested heavily in the gold industry on the one hand to focus on their own business growth, on the other hand to increase China's gold reserves and production. It can be said that to enhance China's strength in the global financial system, it is necessary to strengthen gold reserves and gold mineral exploration and development. This is also one of the means to maintain national economic and financial security.

The funds for gold exploration are getting less and less every year.

It was only the year before last that there were signs of recovery, ▼.

According to the USGS, the global gold reserves are about 53000 tons, of which the proven gold reserves are 33000 tons and the resources (including proved and inferred) are about 120000 tons.

Today, it is mainly stored in Australia (18.87% of global reserves), Russia (14.15%), the United States (5.67%), South Africa (5.09%), Peru (5.09%), Indonesia (4.91%), Brazil (4.53%), Canada (4.15%), China (3.77%) and other countries. China only ranks ninth in the world.

China's gold reserves are really not enough for ▼.

According to the statistical table of China's mineral resources reserves (Ministry of Natural Resources, 2022), China now has proven metal gold reserves of 2964.27 tons and produces 328.98 tons of gold in 2021, a decrease of 9.95% compared with the same period in 2020. At this rate of mining, there will be no more gold in our country after 9 years.

There are only so many gold mines in China.

Output is in a state of negative growth almost every year

(excluding imported raw materials for gold production) ▼

So, why on earth is our country short of funds?

The proportion of associated gold is high, and the grade and scale can not coexist gold resources. According to their occurrence characteristics, we usually divide them into placer gold deposit, rock gold deposit and associated gold deposit.

(figure: wiki) ▼

If we want to find out the difference between these kinds of gold deposits, we should start with their genesis.

"gold" was born out of the sky, came to the earth at the beginning of its formation, and has been largely stored in the depths of the earth in its subsequent evolution. In the process of the formation and evolution of the earth for hundreds of millions of years, magmatism brought gold from the deep part of the earth to the near surface and surface.

In magma, gold has a strong affinity with copper and is usually separated from magma together with copper. Therefore, gold is usually mineralized together with copper, which forms a typical associated ore model in China.

This is also confirmed by China's national mineral resources statistics in 2021. Gold deposits are mainly distributed in Shandong (26.35%), Gansu (9.47%), Yunnan (6.82%), Xizang (6.52%), Jiangxi (5.46%) and Inner Mongolia (5.41%).

Distribution of gold ore reserves in various provinces and regions of China ▼

If you have read our last article "Copper deficiency" (NO. 2335), you will find that there is a strong correlation between gold producing areas and copper producing areas in China. China's associated gold reserves account for 28% of the country's total gold reserves, mostly from copper ore and a small amount from lead-zinc ore.

Gold from copper ores accounts for nearly 80% of the associated gold, ▼.

Associated gold occupies an important position in China, and the proportion of its reserves is larger than the average of associated gold in the world, so associated gold is a major feature of gold resources in China.

This makes the associated gold deposits in China controlled by all the shortcomings of copper deposits.

Porphyry copper deposits are the main copper-producing deposits in China, which are related to the ultra-shallow (neutral-acidic) super-shallow and shallow deposits with high SiO2 content in time and space, and a few medium-deep intrusive bodies (magmatic rocks formed in rocks without eruption).

The large porphyry copper deposits in China are concentrated in Xizang.

(distribution of porphyry copper deposits in China) ▼

However, although porphyry copper deposits account for nearly half of the total copper production in China, in fact, the geological conditions of our country are not suitable for the large-scale formation of such deposits, which is explained in detail in NO. 2335 "Copper deficiency".

Porphyry deposits in China are not at the top of the list in the world, which makes the reserves of gold elements associated with such deposits very limited.

This kind of deposit has four characteristics: one large, two poor, three easy to select and four open mining. It is poor in copper and even poorer in gold, generally no more than 2g / t. As a result, the grade and scale of this kind of gold deposits can not coexist in China, which seriously limits the gold reserves.

Many metallogenic belts of rock deposits are limited rock deposits, which, as the name implies, are deposits occurring in rocks. In the world, the reserve ratio of rock gold, associated gold and placer gold is about 70:15:15, which is the absolute main force of gold production.

The important metallogenic belts of rock gold in China include Shandong Jiaodong gold metallogenic belt, Henan and Shaanxi North China craton metallogenic belt, West Qinling metallogenic belt, Yunnan-Guizhou-Guangxi metallogenic belt, Liaodong gold metallogenic belt and Ailaoshan metallogenic belt.

Distribution map ▼ of Ⅲ grade metallogenic belt of continental gold deposits in China

In fact, Shandong Jiaodong metallogenic belt, Henan and Shaanxi North China craton southern margin metallogenic belt, West Qinling metallogenic belt and Liaodong metallogenic belt are all located in the circum-Pacific metallogenic region.

The Pacific Rim metallogenic region is one of the three major metallogenic regions in the world, with proven gold reserves exceeding 10% of the world's proven reserves, known as the "gold ring". The formation of mineral resources in this area is related to hydrothermal gold deposits.

Scale and location of gold deposits discovered from 2000 to 2011

Gagado ▼ gold deposit in the circum-Pacific metallogenic area

According to modern geoscience, the convergence between plates and the change of mantle composition have made an important contribution to the formation of large-scale hydrothermal gold deposits.

For example, the abnormal enrichment of gold in Shandong Jiaodong gold metallogenic belt, West Qinling metallogenic belt and Liaodong metallogenic belt is closely related to the destruction of North China Craton. It is called "craton destructive gold deposit", and some areas are also known as "orogenic gold deposits".

In previous articles related to mineral resources, we have repeatedly mentioned the concept of "craton". Craton is an ancient continental block, which is a relatively stable geological unit on the surface, including the outermost crust and the top part of the mantle, with a total thickness of about 150-200km, floating on the asthenosphere as a whole.

A simplified illustration of craton formation (figure: EOS) ▼

China's North China Craton was formed in the Proterozoic era, that is, about 2.5 billion years ago, when the earth had just formed land and oceans had not yet been formed, and the earth was far from what it is now. In the subsequent evolution of the earth, the North China Craton remained stable until 150-200 million years ago.

There are three major cratons in the geotectonic division of China:

▼ of North China Craton, Yangtze Craton and Tarim Craton

It is well known that the plates on the earth's surface "float" above the asthenosphere. About 150-200 million years ago, the Eurasian continent where China is located collided with the eastern Pacific plate and continued to converge. This convergence led to the active magmatism and fracture of the North China Craton, which destroyed the stability of the North China Craton for 2.3 billion years. This incident is called "craton destruction".

The magmatic activity caused by "craton failure" brought a large amount of gold-rich magma from the mantle. As a result, the "craton destructive gold deposit" shows the characteristics of short metallogenic duration and huge reserves.

These gold-bearing magmas (hydrothermal fluids) migrate, converge and precipitate along fissures in the shallow crust, thus forming the gold deposits we see now. Therefore, for this kind of gold deposits, large faults deep into the lithosphere are very important for mineralization.

Early Cretaceous subduction of the western Pacific plate

The Mechanism and process of causing the destruction of the North China Craton to indicate ▼

The large-scale Tan-Lu fault zone across the lithospheric scale in the North China Craton is considered to be an important channel for large-scale magmatism and migration and evolution of ore-forming fluids in the process of craton failure. Especially in the large-scale Jiaodong Au ore concentration area, the gold deposits of various mining areas and various mineralization types have the same formation age (120 ±5 Ma;Ma is one million years). The lack of similar deep faults may be an important factor limiting mineralization.

Tan-Lu fault zone

It is the main fault zone in a series of NE-trending giant fault systems on the East Asian continent.

(the three major cratons in China and the Tan-Lu fault zone) ▼

In addition to hydrothermal deposits, metamorphic conglomerate deposits are also important types of rock gold deposits. In the history of gold mining in the world, conglomerate gold deposits play an important role, accounting for 60% to 70% of the world's gold reserves.

One of the most famous is the Rand Gold Mine in South Africa, which has the largest reserves and output of all kinds of gold deposits in the world, providing more than 60% of the world's gold output, which is described in detail in the ball bureau NO. 2315 "South Africa, accidentally dug up the mine". This kind of deposit is distributed in Heilongjiang, Shandong and other places in China, and it is not the main type of gold production in China.

Distribution of Mineral Resources in South Africa ▼

As the name implies, these gold deposits come from metamorphic ancient gold-bearing conglomerates. Gold-bearing conglomerate is a new rock formed by cementing existing gold-bearing gravel.

Conglomerate containing pebble-sized detritus

(figure: wiki) ▼

According to this, we can know that the metamorphic conglomerate was deposited in the basin or delta environment before metamorphism, and there are abundant gold veins in the flow area.

As a result, if we want to form a large metamorphic conglomerate gold deposit, we need a large sedimentary basin, a large amount of water to scour the regional strata, and a large gold-rich geological body. This is all the more necessary to "be in the right place at the right time". Because of this, there is only one Rand gold mine in the world.

Gold was deposited in the Witwater Sland Sea, once an inland lake.

In the river delta and form an outcrop along the Witwater Sland Ridge

Which is what we call the Rand Gold Mine.

Such geological conditions are unique (reference: wiki) ▼

Limited placer gold reserves of sedimentary type placer gold is one of the important sources of gold. China has a wide range of placer gold deposits, ranging from Heilongjiang in the north to the Pearl River and Hainan Island in the south, from the Altay and Brahmaputra rivers in the west to Jiaodong, southern Anhui and Fujian in the east. There are placer gold in many river systems and traces of previous gold panning. The proved reserves account for 13% of the total gold reserves.

The distribution of placer gold in China is indicative of ▼

Placer gold is similar to metamorphic conglomerate type gold deposits, because in fact, metamorphic conglomerate type gold deposits also experienced the stage of placer gold before the consolidation and diagenesis. Therefore, the formation of placer gold mainly depends on three factors: placer gold recharge source, hydrodynamic conditions and geomorphological characteristics.

Placer gold, as the name implies, is as fine as sand.

Different from metamorphic conglomerate gold deposits, modern sedimentary placer gold is no longer covered by sediment, consolidated into rocks, and re-enriched "gold element" in the later geological process.

As a result, although placer gold is widely distributed in China, it is difficult to form deposits with industrial value if there is no very suitable place for deposition.

Sedimentary location of placer gold deposit

(figure: Prospectingplanet) ▼

In addition, the hydrodynamic conditions will directly affect the transport and deposition of placer gold, which determines whether it has industrial value. Major rivers in China, such as Heilongjiang, Yellow River, Yangtze River, Pearl River, Ertix River, Liaohe River and Luanhe River, all produce placer gold.

The distribution of placer gold is not universal. Although placer gold is distributed in the Yangtze River, Yellow River and Ertix River, the grade of placer gold is low, the depth is large, and the particles are generally fine, so it is difficult to utilize at present.

It is not that there is no gold in the river, but that the gold in the river is not easy to use.

The placer gold mineralization in the secondary water system is relatively common, such as Xiangjiang River, Yuanjiang River, Changjiang River, Hanshui River, Luohe River and so on. But the taste is low and the scale is small.

The valley of the 3rd and 4th grade tributaries is not only the main occurrence site of placer gold, but also the main object of industrial development. But there are still shackles of limited scale.

The branch gullies above grade 5 are of small scale and rich in grade, so they are the main objects of popular mining.

It's okay to have fun, but it's hard to get rich.

Generally speaking, because of the scarcity of gold, it is much more difficult to enrich and mineralize than the iron and copper elements we mentioned earlier, and it is also more "dependent on heaven for a living". Although there are rock gold and placer gold deposits in our country, the reserves are very limited, so there is a long way to go to ensure the safety of "gold" mineral resources in our country.

The discovery of a giant single gold deposit in Laizhou, Shandong Province will undoubtedly alleviate the current situation of gold shortage in China to a certain extent, and will further enhance our ability to resist financial risks and ensure economic security.

Reference:

Zhu Rixiang, Sun Weidong. Mantle wedge and craton destructive gold deposit. Chinese Science: Geoscience, 2021, 51. DOI: 10.1360 / SSTe-2020-0305

Zhai Mingguo, 2019. Tectonic evolution of North China Craton. Journal of geomechanics, 25 (5): 722-745. DOI: 10.12090 / j.issn.1006-6616.2019.25.05.063

[3] Mineral Commodity Summaries 2021 (usgs.gov), pp71

[4] https://www.mnr.gov.cn/sj/sjfw/kc_19263/kczycltjb/202208/t20220826_2757756.html;

Wang Zaicong, Wang Yan, Wang Xiang, et al., 2021. Metasomatism of lithospheric mantle and gold mineralization. Geoscience, 46 (12): 4197-4229.

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