The strata from Mesoproterozoic to Quaternary in Guangxi are well distributed and developed, with 12 series and 2 formations * * * 120 stratigraphic units (Table 2-2). The total sedimentary thickness is about 76000m, and there are many rock (ore) layers that provide ore sources for weathered deposits.

1. Yuangu language

Mesoproterozoic to Neoproterozoic are distributed from Jiuwandashan in northern Guangxi to Yuechengling and Yunkaishan in southeastern Guangxi, which are summarized as follows.

(1) Bao Si Group of Jixian System (Ptsh)

This formation is the earliest metamorphic rock exposed in Guangxi, and it is divided into nine groups from bottom to top, Wentong Formation and Yuxi Formation, all of which are shallow metamorphic sandstone and mudstone. The Wentong Formation contains six layers of basic lava, tuff and Komate rock, the thickness of which is greater than 704m, 265,438m+0.865,438m and 5,700m respectively.

Yunkai area is metamorphic flat granulite with a thickness of1832 m.

(2) Danzhou Group (Pt3t)

Sanmen area in Longsheng is composed of metamorphic sandstone mudstone and carbonate rock, sandwiched with three layers of spilite porphyry. The total thickness is 968~4780m. Northeast Guangxi is divided into Yingyangguan Formation and Nantuo Formation. It is sedimentary metamorphic magnetite with a thickness of 20m, mixed with metamorphic amphibole and pyroclastic rocks with a thickness of 14 13 ~ 2090 m.

(3) South China (Nh)

Northern Guangxi is divided into Chang 'an Formation, Fulu Formation and Nantuo Formation, which are composed of shallow metamorphic sandstone, slate and thin hematite with a thickness of 299～4859m m. ..

(4) Sinian system (Z)

It consists of Doushantuo Formation and Laobao Formation. Doushantuo Formation consists of dolomite sandwiched with carbonaceous shale and siliceous shale containing manganese, phosphorus and pyrite nodules. Laobao siliceous rocks are 52 ~ 485 m thick, belonging to Pei Di Formation in the southeast of Guangxi, and are metamorphic sandstone and siliceous rocks with thickness > >1303 m.

2. Paleozoic. Originally known as PRIMARY

(1) CAMBRIAN

The geographical division of northern Guangxi is divided into Bian Xi Formation and Qingxi Formation. The lower shale of Bian Xi Formation is mixed with a small amount of limestone, and the upper shale is interbedded with sandstone and mudstone. The carbonaceous shale of Qingxi Formation is interbedded with siliceous rocks and sandy shale, and the upper part is limestone and dolomitic limestone, with a thickness of 1029 ~ 3 157m. Guidong area is divided into Xiaonenchong Formation and Huangdongkou Formation, which are clastic rocks with flysch formation and turbidite deposits in trough basin, with a thickness of1221~ 6817m.

The western Guangxi is dominated by platform carbonate rocks, and the middle-upper Longha Formation is dolomite, argillaceous banded limestone, siltstone and sandstone, containing trilobite fossils, with a thickness of about 6800m m. The upper series is composed of Tangjiaba Formation, Bochetian Formation and Sandu Formation, and the sandstone shale is a transitional phase with a thickness of1020 ~ 2095 m..

Table 2-2 Survey of Stratigraphic Units and Minerals in Guangxi *

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(2) Ordovician

The lower series in northern Guangxi is divided into limestone and dolomite of Baidong Formation. Huang 'ai Formation sandstone shale and conglomerate interbedded; The black shale and carbonaceous shale of Shengping Formation are interbedded with sandstone, with a thickness of 6 18 ~ 48 13m. The middle series consists of flysch, sand and shale interbeds, including graptolite, with a thickness of 298 ~ 478 meters. The sandstone shale with flysch rhythm of Upper Series is rich in graptolites, with a thickness of 673 ~ 1304 m. ..

There are only Liu Chen Formation and Huang 'ai Formation in the Lower Triassic in southeastern Guangxi, and the former is mixed with thick sandstone. There are sporadic outcrops in the upper series, mainly clastic rocks. Manganese-bearing siderite is sandwiched between Lingshan in Rongxian County and Panlong in Yangmei Beiliu, with a thickness of 830 ~ 1207m.

(3) Silurian system

Mainly distributed in the south and southeast of Guangxi. Collectively called Lingshan Group, its lower part is Tianlinkou Formation in northern Guangxi, and there are 3 ~ 4 layers of siderite and sand shale interbedded in the southeast of Guangxi, with a thickness of 781~ 6745 m. ..

(4) Devonian

There are various types of Devonian sediments in Guangxi, which can be roughly divided into 7 facies zones according to the book Devonian in Guangxi. That is, coastal clastic rocks, carbonate confined platforms, open platforms, platform margins, platform front slopes, platform trenches, trough basins and other facies, and each facies has a corresponding representative stratigraphic group (Table 2-3).

According to the regional metallogenic research in Guangxi, the statistical results of background distribution characteristics of stratigraphic elements are shown in Table 2-4.

Except Zr, more than 20 other elements were relatively enriched in Permian, Carboniferous and Devonian. The concentration in Clark area is greater than 283× 10-9.

The gold and silver background values of Devonian, Carboniferous and Permian are the highest.

The background values of Pb, Zn and Sn in Devonian, Carboniferous and Permian are the highest, which are completely consistent with the occurrence horizons of major lead-zinc deposits in Guangxi. For example, Nandan Dachang 100 # are all located on the D2-D3 horizon.

Devonian, Carboniferous and Permian have the highest manganese background, which is quite consistent with the manganese-bearing horizons D3l, D3w, C 1d, P2g and T 1b in Guangxi.

Table 2-3 List of Devonian Strata and Sedimentary Facies in Guangxi

Table 2-4 Distribution Characteristics of Formation Elements Background

(5) Carboniferous (C)

The Carboniferous in Guangxi inherited the sedimentary characteristics of the Late Devonian, including 23 stratigraphic units. According to Kuang's research in 2000, western Guangxi can be roughly divided into open platform facies, platform margin facies and platform gully facies, and each facies area has a representative stratigraphic name (Table 2-5 and Table 2-6).

Table 2-5 Carboniferous Division and Sedimentary Facies in Western Guangxi

Table 2-6 Division of Carboniferous Sedimentary Facies in Southern Guangxi and Northern Guangxi

The Carboniferous sedimentary facies in southern Guangxi and northern Guangxi are quite different, but according to the data of Kuang et al, they can be roughly divided into shallow water and deep water. The upper or top of the Datang terrace deposited in platform trench facies or continental shelf often contains 1 ~ 4 layers of manganese deposits, which form manganese cap-type or accumulation-type manganese deposits after weathering.

(6) Permian

See Table 2-7 for the division of Permian sedimentary facies belts. The Lower Permian Maping limestone and the former Upper Carboniferous limestone were limestone, which could not be separated in the field in the past. There are thin coal measures at the bottom of Qixia Formation in northern Guangxi, and Gufeng Formation (out of phase with Maokou Formation at the same time) is located in the east of Yongfu-Luzhai-Luo Rong-Xincheng-Laibin-Guigang and other areas. It belongs to deep-water deposition of Taigou facies, with siliceous rocks mixed with limestone, manganese-bearing siliceous rocks and manganese-bearing limestone 1 ~ 5 layers, with a thickness of 54 ~ 2 14m. Qinzhou area is a weathered and leached siliceous manganese oxide deposit with 13 layers of manganese mudstone.

Heshan Formation is 0 ~ 543 m thick with coal, aluminum, iron, pyrite and clay at the bottom, which is one of the main ore-bearing strata in Guangxi. Above the erosion surface of Maokou Formation at the bottom, there is a sedimentary bauxite layer in western Guangxi, with coal 1 ~ 5 layers at the bottom and coal1~12 layers in Xincheng-Shanglin area. There is 1 ~ 3 siderite layer in the upper part of Dongluo-Quxiang area in southwest Guangxi, and the ore grade TFE is 24.8% ~ 35%. After surface weathering, accumulated bauxite deposits are formed. Above Heshan Formation is Dalong Formation, with sand shale mixed with thin layers of siliceous rocks, volcanic rocks and limestone, and the thickness is 10 ~ 1 14m.

Table 2-7 Division Table of Permian Sedimentary Facies in Guangxi

3. Middle school

Lower Triassic (1)

Luolou Group is widely distributed in the shallow shelf facies in western and southwestern Guangxi, which is mudstone and argillaceous limestone, mainly basic volcanic rocks. Pingerguan in Longzhou has extremely thick acidic volcanic rocks, with a thickness of 37 659m m. Majiaoling Formation in platform margin and slope facies is composed of thin limestone, marl mixed with dolomite and oolitic limestone, with a thickness of10 749 m. The upper part of Beisi Formation is limited platform facies dolomite. There is a manganese-bearing limestone with a thickness of 37 659m at the junction of Tiandeng, Debao and Tianyang counties, and there is a 13 manganese deposit in the upper part of Beisi Formation in Dongping area of Tiandeng.

(2) Middle Triassic (T2)

The restricted platform facies is Hekou Formation. The former is limestone, argillaceous banded limestone and dolomite; The latter is interbedded sandstone and mudstone. The terrigenous clastic turbidite in the trough basin is called Baifeng Formation, which belongs to flysch deposit and Ma Bao system, with a thickness of1252 6484m.

(3) Upper Triassic (T3)

Pingdong Formation and Longfu 'ao Formation are distributed in the southern foot of Shiwan Mountain, and belong to the alternating strata of land and sea. Pingdong Formation is purplish red glutenite, with rhyolite porphyry mixed with perlite and tuff lava at the bottom, and the angle is unconformity on Indosinian granite. Shanglong Fuao is composed of purplish red glutenite, sandstone and siltstone mixed with conglomerate, and the coal seam line 13 15 all produces marine septum fossils with a thickness of 425.

4552 meters.

(4) Jurassic (J)

The areas east of Guidong, Guinan and Gongning Line belong to inland rift basin deposits, which are divided into Middle Tang Tian Formation, Daling Formation, Shiti Formation and Hexian Xiwan Formation, with 2 ~ 7 coal layers. Shiwandashan Group belongs to lake facies or swamp facies, and Xiawangmen Formation, Baixing Formation, Zhongnadang Formation, Shangqili Formation and Dongxing Formation are all inland lake facies deposits.

(5) Cretaceous

It is distributed in southeast, south and northeast Guangxi, and belongs to lacustrine or fluvial deposits in inland rift basins. The lower part is divided into Xinlong Formation, Dapo Formation and Pisces Formation, and the upper part is divided into Dong Xi Formation and Tam Formation.

Xinlong Formation in Sanlong area of Lingshan is red sandstone mudstone with a thickness of 80 2445 m, and there are more than 30-60 thin gypsum layers in the upper part, and the thickness of single gypsum layer is10 200mm.

Dong Xi Formation consists of variegated conglomerate, tuff, rhyolite, quartz porphyry and andesite. There are obsidian, perlite and zeolite in the hydrological basin of Cenxi City, with a thickness of 102 738m.

4. the new world

(1) Paleogene (East)

Exposed in southern Guangxi and along the Youjiang River in Baise. Baise basin is divided into six groups of red sandstone and mudstone from Paleocene to Eocene, and the upper part is gypsum with a thickness of 34 ~ 367 m.

Eocene in Baise basin is divided into Dong Jun Formation (thickness1618m), Nadu Formation (thickness 50 1000m) and Baigang Formation (thickness1kloc-0/3625m), which contains multiple layers of coal. Nanning Basin and Shangsi Basin are called Yongning Group (Ey) and contain coal.

Oligocene is divided into Fuping Formation and Jianduling Formation, containing a large number of vertebrate fossils and gastropods, with a total thickness of 3 19 1058m.

There are lignite and refractory clay in Yongning Group of Nanning Basin. There are 9 layers of bentonite in Ningming basin. There are 1 4 layers of lignite in Haiyuan basin.

(2) Neogene

Only distributed in Nankang, Weizhou Island and Xieyang Island in Hepu County, it is called Nankang Group. The lithology is grayish white sand, siltstone, glutenite mixed with lignite and inferior oil shale. Weizhou Island and Xieyang Island are sandwiched with 47 378m thick olivine basalt and volcanic breccia. ..

(3) Quaternary (Q)

Quaternary is divided into cave accumulation, river alluvial deposit and coastal deposit, as shown in Table 2-8.

Table 2-8 Summary of Quaternary Division in Guangxi

1) cave development in central Guangxi: according to cave accumulation and Pleistocene series of animal fossils, it is divided into Liucheng Formation (including Bubu period great ape fossils), which is equivalent to a fourth terrace with an altitude of 80110m; Daping Formation is equivalent to the third terrace, which is 50 ~ 9m above the water surface. Xinxing formation (including fossils of Liujiang people, Laibin people and giant pandas) developed in secondary terrace caves; Qianjiang Formation is developed in a first-class karst cave, with variegated clay and animal fossils.

2) River alluvium: mainly distributed on the banks of Zuojiang River, Youjiang River, Yujiang River, Jiang Xun River, Yongjiang River and Liujiang River. Pleistocene is divided into Jiang Xun Formation, Baisha Formation and Wang Gao Formation. The Holocene is divided into Guiping Formation and floodplain deposits (Table 2-8).

3) Coastal sediments: distributed in Beihai, Hepu and Dongxing coastal areas, Weizhou Island and Xieyang Island, with Pleistocene Beihai Formation, Pingjiang Formation and Holocene.

There are placer tin deposits in Quaternary in northeastern Guangxi, Nandan, Fuhe and He Zhong, placer gold associated rare earth deposits in Shanglin and Beiliu Longsheng, residual and alluvial ilmenite deposits in southeastern Guangxi and Xibama, and crystal placer deposits in karst depressions in western Guangxi. Laterite bauxite is distributed on the karst ancient platform (planation plane) in central and southeast Guangxi.

Second, magmatic rocks

There are magmatic activities in Guangxi from Mesoproterozoic to Cenozoic with complex lithology, which can be divided into volcanic rocks and intrusive rocks as follows.

1. Volcanic rocks in Guangxi

Volcanic rocks in Bao Si and Xuefeng periods are mainly distributed in northern Guangxi. Variscan and Indosinian volcanic rocks are mainly distributed in western and southwestern Guangxi. Yanshanian volcanic rocks are mainly distributed in basins in southeastern Guangxi; Himalayan volcanic rocks are exposed in coastal islands. There are 46 cycles of volcanic eruption with a thickness of about 9000m (Table 2-9).

(1) Volcanic rocks in Bao Si

Distributed in Jiuwandashan and Yuanbaoshan, produced in Wentong Formation and Yuxi Formation.

The lower member of Wentong Formation is only1~ 2m thick altered basic tuff. The upper member of Wentong Formation has six layers, representing six cycles. Volcanic rocks mainly include tholeiite, basaltic Komatiite, basaltic pyroclastic rocks and associated volcanic jet deposits.

The volcanic rocks of Yuxi Formation are only distributed in the south of Tian Peng rock mass, with 1 ~ 3 layers, which are intermediate-acid tuffs.

(2) Volcanic rocks in Xuefeng period

It is distributed in Sanmen, Longsheng and Yin-Yang Pass of Hexian County, and is produced in Tanghe Formation of Danzhou Group.

Both areas are composed of three eruption cycles, all of which are spilite-keratophyre assemblages. The iron ore with industrial value is located at the top of Yinyangguan sodium-rich volcanic rock.

(3) Caledonian period

There is a layer of altered basic lava at the bottom of Ordovician in Guanyang county and Damingshan area, with a thickness of 20 ~ 80 m, and the Lower Silurian in Taiping and Dashuang areas of Cenxi city is sandwiched with volcanic breccia, amphibole and amphibole, with a total thickness of > > 80 m.

(4) Huali Western Regions Period

It is distributed in the west of Guangxi, and only a small area is exposed in some areas.

1) The lower Devonian Mo Ding Formation almond-shaped basalt mixed with siliceous belt, with a thickness of 80 ~ 100 m, is produced in Ba Du, Tianlin.

2) Banmeng and Kejia in Longzhou County have basaltic porphyry, trachyte porphyry and tuff lava of Donggangling Formation of Middle Devonian, with a thickness of 10~50m ~ 50m.

3) Upper Devonian basaltic porphyry and trachyte porphyry occur in Ande, Banmeng, Kejia in Jingxi County and Wude in Longzhou County, with a thickness of 1 ~ 50m.

4) Lower Carboniferous basalt, tuff and volcanic breccia tuff, with a thickness of 12 ~ 73m, are produced in Longlin, Ludong and Longna of Jingxi County.

5) The volcanic rocks of Maokou Formation in Middle Permian are composed of basalt, basaltic tuff, agglomerate and lava, with a thickness of 2 15m. The Upper Permian in western Guangxi is dominated by basalt, which evolved from basic-neutral to acidic from northwest to southeast, and the horizon gradually increased. There are often titanomagnetite deposits in Quaternary nearby.

Table 2-9 Histogram of Volcanic Eruption Characteristics in Different Periods in Guangxi

(5) Indosinian volcanic rocks

Volcanic activity in this period was the strongest in Guangxi, with basic-intermediate acid marine eruption in the early and middle Triassic and acid volcanic eruption in the late Triassic.

1) Lower Triassic volcanic rocks: Napo area is basalt, Pingxiang area is acidic and moderately acidic lava, with a thickness of 197 ~ 2022 m, scattered in Pingguo, Guigang and Pingle.

2) The Middle Triassic volcanic rocks are distributed in Chongzuo, Ningming, Napo and Nandan, which are acid lava and tuff breccia. There is dacite porphyrite in Jiangzhou, Chongzuo, with a thickness of100 ~ 500m.

3) Upper Triassic volcanic rocks: distributed in Long Fu Depression-Banba Cave at the southern foot of Shiwandashan Mountain, mainly rhyolite porphyry, with a thickness of 236-620m. ..

(6) Yanshanian volcanic rocks

It is mainly distributed in Cenxi-Bobai fault and Lingshan-tengxian fault. In the late Cretaceous, there were1~ 4 eruption cycles in the fault basins such as Dingshan, Baisong, Bailiang, Gupang, Zhougongding, Shuiwen, Yulin Shuijuntang, Bobai, Baisha and Beiliu Liu Ma, which were composed of tuff breccia, felsic, quartz porphyry and dacite. Related minerals: zeolite and perlite in Shuiwen basin, agate in Bobai and Du 'an basins.

(7) Himalayan volcanic rocks

Only in Yandunling, Weizhou Island and Xieyang Island, Hepu, three olivine basalts erupted.

2. intrusive rocks

Guangxi regional geological survey team found intrusive rocks about 1200, covering an area of about 20000km2, accounting for 8.5% of the total area, mainly distributed in northern Guangxi, northeastern Guangxi, southeastern Guangxi and western Guangxi. Magmatic activities in different periods control the formation of endogenetic deposits in Guangxi, which is closely related to the formation of nonferrous metal minerals, rare earth dispersion and rare metal minerals. In particular, most granite weathering crusts have ion adsorption rare earth deposits or mineral rare earth deposits, forming another dominant mineral species in Guangxi. The area of intrusive rocks and related mineral resources in each period are summarized in Table 2- 10.

What needs to be explained here is that our Map of Metallogenic Regularity of Weathered Deposits in Guangxi adopts the Digital Geological Map of People's Republic of China (PRC) in 2007 (Guangxi Part) compiled by the Institute of Chinese Academy of Geological Sciences as the geological base map. In this figure, intrusive rocks are represented by geological age, while in this book, intrusive rocks are represented by tectonic movement names in order to facilitate the dissolution of the two.

Table 2- 10 Classification of Granites (Rock Groups and Rocks) in Different Periods in Guangxi and List of Related Minerals

sequential

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sequential

Through, compare them with the following:

Bausch period includes all kinds of granites in Mesoproterozoic; Xuefeng period contains late Proterozoic granite; Caledonian (γ3) contains early Paleozoic granite; Variscan (γ4) contains late Paleozoic granite (D-P); Indosinian epoch contains Triassic granite; Early Yanshanian Jurassic granite; Late Yanshanian granite, including Cretaceous granite.

(1) Bao Si intrusive rocks

The intrusive rocks in this period can be divided into two types: ultrabasic rocks-basic-neutral intrusive rocks. It is distributed in Jiuwan Mountain, Luocheng Baotan and Rongshui forested area. The other is intermediate-acid intrusive rocks, distributed in Luocheng and Rongshui, including Dongben, Caigun, Longyou, Xiangfen, Dapoling, Mengdongkou, Sanfang, Yuanbaoshan, Pingying and Qingming Mountain.

The related minerals in this period include copper, nickel, serpentine, asbestos, platinum, palladium and tin.

(2) Xuefeng intrusive rock

Ultra-basic-basic-neutral intrusive rocks, distributed in Sanmen and Hekou areas of Longsheng, are related to minerals such as copper, nickel, cobalt and palladium.

(3) Caledonian granite

1) remelted granite, distributed in Yuechengling, Maoershan, Haiyang, Dupangling (Xiti), Lingzu, Xinzhai, Luoping and Qinjia in Debao County, northeast Guangxi. The related minerals are tungsten and tin.

2) The syntectic granodiorites related to gold and silver deposits are Daning and Yonghe.

3) metasomatic granite: distributed in southeast Guangxi, with intrusions such as Beijie, Liu Jing, Jialong, Yongbiao, Hongtaizhai and Hengshan, mainly related to weathered deposits such as ilmenite and rare earth minerals.

(4) Variscan intrusive rocks

1) Basic layered intrusions: distributed in Bama, Longlin, Yilong, Yangwei, Ba Du and Xiabu in Jingxi County, with three lithologic combinations: a. Diabase type; B. Diabase-diabase type; C biotite lherzolite-gabbro type. But most of them should be marine volcanic rocks. Rock masses A and B contain 2% to 4% ilmenite.

2) Variscan Granite: It is a giant rock belt with a length of about 375km and a width of about 75km, which is distributed at the southern foot of Rong Da Mountain, Liuwan Mountain and Shiwan Mountain, and its emplacement gradually increases from northeast to southwest. The rock mass is generally rich in ilmenite, which is related to lead-zinc minerals.

(5) Indosinian intrusive rocks

1) ultrabasic-basic intrusive rocks: Seven small rock belts and dikes distributed along Pingxiang deep fault invaded Carboniferous-Middle Triassic. The main lithology is pyroxene peridotite and gabbro, and the related minerals are titanium and gold.

2) Granite: distributed in Shinan-Fangcheng, Qinzhou Temple, Matai, Gai Na, Renyin, carved eagle Ridge, Liang Na and other places, as well as in eastern Guangxi, northeastern Guangxi, Guiping and Pingxiang.

During this period, ilmenite deposits were mainly formed in the weathering crust of quartz diorite complex in Cenxi-tengxian area.

(6) Yanshanian intrusive rocks

1) ultrabasic-basic intrusive rocks: only found in Xiangshan, Wang Fu, Pubei County, with an area of 0.7km2, consisting of pyroxenite-gabbro and a small amount of olivine gabbro. Trace elements contain 5% Cr, so some people think that chromium ore may be formed in the deep.

2) Early Yanshanian granites: remelting granites are distributed in northeast, southeast and central Guangxi, including Limu, Dupangling East, Yinding Shanhuashan, Guposhan, Jinjiding, Changgangding and Guangping. The contact zone is related to tungsten, tin, iron, niobium and tantalum, and the weathering crust of rock mass contains ion adsorption rare earth and mineral rare earth minerals.

3) The third type of syntectic granite in the early Yanshanian period: Mashan in Hengxian County, Du Nan in Rongxian County, Luo Rong in Guiping County, Fenghuangling, clear lake in Luchuan County, Xia Ying in Cangwu County and Nan 'an County. Granodiorite-quartz diorite-diorite-basic rock is mostly complex, and the weathering crust is related to ilmenite and ion-adsorbed rare earth ore.

4) Late Yanshanian granites: including Kunlun Pass, Luchuan, Dachang Cage Box Cover, Xie Xianzhang, Michang, Dawangling, Baiyu Y and Sanchachong, as well as sporadic small rock masses such as Yingqiao, Doudong, Sheshan, Guogailing and Yapoling in Shengzhou, which are mainly related to tungsten, molybdenum, lead, zinc and ion adsorption rare earth minerals in weathering crust.

Three, coal seam (body) and ore-bearing rock mass (layer)

1. iron-bearing horizon

Iron ore: known iron-bearing horizon in Guangxi 1 1 (Table 2- 1 1). After long-term surface weathering, limonite is mostly formed, especially in the Silurian Lingshan Group in Qinzhou-Lingshan area of southern Guangxi, which contains 1 ~ 8 layers of pyrite. After weathering, limonite often forms iron hat type or accumulation type.

Table 2- 1 1 General situation of iron-bearing strata in Guangxi

2. Manganese-bearing horizon

The known manganese-bearing horizons in Guangxi are 1 1 (Table 2- 12), in which Devonian, Carboniferous Datang Formation, Permian Gufeng Formation and Lower Triassic Beisi Formation are all economically valuable manganese-bearing horizons, all of which are platform-gully facies deposits.

Table 2- 12 General situation of manganese-bearing layer in Guangxi

(1) Devonian manganese-bearing rock series

Distributed in southwest, middle and southeast Guangxi. There are 2 ~ 3 manganese-bearing layers, which are located in the middle and lower parts of Liujiang Formation and Wuzhishan Formation respectively. Mainly manganese-bearing siliceous rocks and manganese-bearing limestone. The ore belongs to the type of rhodochrosite-manganese-containing carbonate rock, and accumulated manganese oxide deposits and hat-shaped manganese oxide deposits are mostly formed after weathering.

(2) Lower Carboniferous manganese-bearing rock series

Distributed in western Guangxi, Nanning-Mashan, Liuzhou-Pingle and Nandan-Yishan. There are four layers of manganese carbonate sandwiched with manganese limestone in the middle of Datang Formation in central Guangxi, and the upper part is composed of manganese limestone sandwiched with 1 6 manganese carbonate layer, which can form weathered deposits.

(3) Middle Permian manganese-bearing rock series

It is distributed in central Guangxi, western Guangxi, northeastern Guangxi, eastern Guangxi and Qinzhou Dazhi-Fangcheng Tanying. Manganese-bearing horizons are inconsistent. Quanzhou and Liuzhou are located in the upper part of Gufeng Formation, and Qinzhou-Fangcheng area is located at the bottom.

Xing 'an and Quanzhou Gufeng Formation are manganese-bearing siliceous rocks, Liuzhou-Laibin is manganese-bearing limestone and manganese carbonate deposits, and Qinzhou-Fangcheng Gufeng Formation is manganese-bearing siliceous rocks and manganese-bearing siliceous mudstone, with a total of four manganese-bearing horizons. Weathered deposits can be formed.

(4) Manganese-bearing rock series of Lower Triassic Beisi Formation.

Dongping, Jiangcheng, Pingyao, Dawang and Longyan are located at the junction of Tiandeng, Tiandong and Debao counties. It is manganese-containing argillaceous siliceous limestone with manganese carbonate layer, which forms better weathered sediments after weathering.

(5) Jurassic manganese-bearing rock series

It is distributed in the Xiwan Basin of Hexian County, and the lower Jurassic Tang Tian Formation is a manganese-bearing rock series. It is manganese-bearing mudstone, manganese-bearing shale and manganese-bearing nodule, which can be enriched to form accumulated manganese ore after local weathering, such as Fanglin in Hexian County.

3. Al-bearing rock series at the bottom of Upper Permian

Widely distributed in western and southwestern Guangxi. Located at the bottom of the Upper Permian Heshan Formation and on the erosion surface of the Middle Permian Maokou Formation, there are sedimentary bauxite and siderite. Weathering and denudation form accumulative bauxite deposits and lateritic bauxite deposits.

4. Granite-related minerals

See table 2- 13 for the relationship between the mineralization of weathered minerals in Guangxi and granites in different periods. According to the statistics of Guangxi Reguiyuan 1996, as shown in Table 2- 14, weathered crust sand deposits can be formed by weathering and enrichment of accessory minerals near rock plants, and then river terraces and coastal sand deposits are often formed by flowing water.

Bao Si granite is related to tin ore (chloritization, Dianying); Caledonian granites are related to tin, tungsten, gold and kaolin. Variscan-Indosinian intermediate acid rocks are related to ilmenite and ion-adsorbed rare earth minerals. Granites in the early Yanshan period are generally closely related to ion adsorption of rare earth, mineral rare earth and rare metal minerals. For example, the weathering crust of Guposhan granite body is rich in brown yttrium ore, black rare gold ore and monazite. The late Yanshanian granite is related to tungsten, tin, ions, rare earth minerals and placer gold.

5. Relationship between ore bodies and weathered deposits

Ore bodies are often directly related to weathering deposits, and the material source determines the minerals of weathering deposits. Generally, local materials are used, reformed or slightly replaced, and weathered deposits such as weathered crust residual slope deposit, mine cap type, leaching type and accumulation type are formed on the upper part or surface of primary ore bodies.

Endogenous metal sulfide deposits in northern and southeastern Guangxi are formed by weathering and leaching on the surface or shallow part, such as lead-zinc pyrite in Beishan area along the Yangtze River, tin polymetallic ore body in Danchi area and polymetallic pyrite body in southeastern Guangxi. Iron hat limonite is often distributed on the surface. The timely primary calcite vein deposits and crystal-bearing occurrences in northwest Guangxi mostly form crystal placers in the surrounding karst depressions after weathering. Granular gold deposits have iron caps and ion-adsorbed gold deposits.

Table 2- 13 List of Relationship between Granite and Weathered Minerals in Different Periods

Table 2- 14 Statistics of Primary and Secondary Minerals in Granite in Different Periods (average gross unit is g/t)