1. Regional geological characteristics
(1) regional stratum
This area is located in the southern margin of anticlinorium, Taihang Mountain, Shanxi fault uplift in North China landmass. This stratum is a typical sedimentary area type in North China, belonging to Xinxi sub-region of North China Stratigraphic Area.
The stratum is composed of basement and caprock, and has a typical double-layer structure. The basement is mainly composed of Archean medium-deep metamorphic rocks and metamorphic Guyu shallow metamorphic rocks, and its lithology includes various gneiss, schist, quartzite, seasonal sandstone and a small amount of mudstone and carbonate rocks. The caprocks are Cambrian and Ordovician in Lower Paleozoic, Carboniferous and Permian in Upper Paleozoic and Mesozoic and Cenozoic strata.
Due to the influence of Caledonian movement, the crustal uplift suffered denudation from late Ordovician to early Carboniferous, resulting in the loss of upper Ordovician, Silurian, Devonian and lower Carboniferous strata. Ordovician carbonate strata are weathered and denuded to varying degrees. Benxi formation of Middle Carboniferous is a set of iron-aluminum rock series (bauxite ore-bearing rock series), which is directly unconformity with Ordovician. Therefore, the weathering and denudation products of Ordovician carbonate rocks are the main sources of bauxite. Taiyuan Formation and Permian of Upper Carboniferous are a set of coal-bearing strata, the thickness of which exceeds 1000 m, which constitute the overlying strata of bauxite. The main coal seams in Shanxi Formation of bioclastic limestone and Taiyuan Formation are obvious prospecting indicators of bauxite.
(2) Regional structure
This area is located in the southwest edge of North China Platform, with Qinling and Zhongtiaoshan fold uplift belts with strong long-term tectonic activity on the north and south sides. The obvious feature of the tectonic framework is the alternation of uplift and depression. This pattern of alternating ups and downs controlled the development and distribution of Paleozoic strata, as well as the third and fourth tectonic basins and synclines of Mesozoic and Cenozoic. From north to south, the work area is Zhongtiaoshan ancient uplift, Daimenzhai ancient uplift, Songshan uplift, Jishan uplift and Luogu ancient uplift, among which Qinyang-Kaifeng sag, Mianchi sag, Yiyang sag, Dengfeng sag and Linxiang sag are distributed. These depressions are generally characterized by syncline structures, such as Mianchi syncline, Luoxing syncline, Dengmi syncline, Yuxian syncline and Linxiang syncline. Bauxite is mainly distributed in its marginal zone.
(3) Magmatic rocks
Regional magmatic rocks are not developed, but only exposed in Shaanxi and Mianchi. The occurrence time is Mesozoic, and the lithology is amphibolite porphyry and granite porphyry.
2. Geological characteristics of the evaluation area
This mineral evaluation work is divided into four evaluation areas: Mianchi Lizhuangzhai Bauxite Evaluation Area, Xin 'an Yushan Bauxite Evaluation Area, Jiyuan Summer Night Bauxite Evaluation Area and Jiyuan Dashe-Fansi Bauxite Evaluation Area.
Lizhuangzhai Bauxite Evaluation Area is located in Lizhuangzhai, Potou Township, Mianchi County, Henan Province. From Chengtou in the west to Ganjian in the east, it is 1 1.5km long from east to west, 5.0km wide from north to south and covers an area of 57.0km2.
(1) stratum
The working area belongs to the western section of Xin 'an Grade IV bauxite metallogenic area in Mianchi, Shaanxi Province. The exposed strata in the area are Mesoproterozoic Beidajian Formation, Neoproterozoic Cuizhuang Formation, Sanchang Formation, Cambrian, Ordovician, Carboniferous benxi formation and Taiyuan Formation and Permian, which are mainly distributed in the northeast of the evaluation area. This area is covered by Quaternary, and Neogene is scattered in this area.
(2) Structure
The evaluation area is located in the north of Mianchi sag, with monoclinic structure and southwest dip angle of 65438+03 ~ 27. The fault structure in this area is not developed.
(3) Characteristics of Al-bearing rock series
Benxi formation is a set of aluminum-bearing rock series, which is exposed in Ganjian area on the eastern edge of the evaluation area, with sporadic exposure in Honglingpo area in the northwest. The aluminum-bearing rock series in the lower part of Quaternary overburden in the evaluation area is stable, with a thickness of 3.34 ~ 18.04 m, which is dark gray or gray-white thin claystone or bauxite layer and yellow iron-bearing claystone. Thick layered bauxite with gray and dark gray is distributed in the middle and upper part of clayey rock, with a pea-shaped oolitic and clastic structure, and sometimes a granular structure and a massive structure. Porous structure and honeycomb structure can be seen in the weathering zone near the surface. In the deep holes ZK6304 and ZK3 10 1 in the west of the evaluation area, clay rocks contain a large amount of pyrite, which is in the form of fine grains or blocks, with the content of 1% ~ 30%.
3. Geological characteristics of the deposit
(1) Ore body shape, occurrence and scale
Two bauxite bodies have been preliminarily delineated, and the estimated bauxite resources are 3888× 104t.
Orebody I: Located in the northeast of Dongtiantan Village in the east of the evaluation area (line 9 -2), it belongs to shallow concealed orebody and is controlled by two boreholes ZK070 1 and ZK 00 1. The ore body is layered, with strike length1200m and dip extension of 400m, and thickness1.34 ~ 2. Ore content: Al2O3 41.87% ~ 61.74%, coefficient of variation 34%, with an average of 58.61%; SiO 29.34% ~ 17.99%, coefficient of variation 55%, average15.64%; The A/S (aluminum-silicon ratio) value is 1.9 1 ~ 7.47, and the coefficient of variation is 148%, with an average of 3.75. The estimated (334 1) resource is 252.58× 104t.
Ore body ⅱ is located in the middle of the evaluation area and belongs to shallow-buried ore body. The surface is controlled by TC0 1 from west to east, and the middle and deep parts are controlled by ZK630 1, ZK6304, ZK590 1, ZK5504, ZK470 1, ZK390 1 and ZK390. The ore body is in irregular strip shape, with a strike of 4500 meters long and a dip extension of 400 ~ 600 meters. The thickness of ore body is 0.94 ~ 17.36m, and the coefficient of thickness variation is 138%, with an average of 5.71m; . Ore content: Al2O340.60%~67.48% ~ 67.48%, coefficient of variation 37%, average 58.83%; SiO 26.39% ~ 23.76%, the coefficient of variation is 72. 1 1%, and the average value is13.69%; The A/S value is 2.30 ~ 1 1.30, with an average of 4.30 and a coefficient of variation of 84%. The estimated resource is 3636.46× 104t.
From west to east, the content of Al2O3 in the ore gradually decreased, the content of SiO2 gradually increased, the A/S value also decreased, the quality grade of the ore gradually decreased, and the local phase changed into clay ore.
In the vertical direction, from top to bottom, the content of Al2O3 in aluminum-bearing rock series gradually decreases, the content of SiO2 and Fe2O3 gradually increases, the A/S value decreases synchronously, the quality grade of ore gradually decreases, and the local phase becomes clay ore or iron ore.
The thickness of Lizhuangzhai bauxite ore body changes greatly and is unstable, and the thickness of aluminum-bearing rock series is generally positively correlated with bauxite, that is, the thickness of aluminum-bearing rock series is large and the bauxite layer is thick and rich.
(2) the structure of ore
1) Ore structure: The ore is of bean-like oolitic structure, clastic structure and aphanitic structure.
2) Structure: mainly block structure, directional structure, layered structure and honeycomb structure.
(3) Ore type
According to the ore structure, it can be divided into dense massive bauxite, clastic oolitic bauxite and honeycomb bauxite. Bauxite ores are mainly clastic and oolitic bauxite, accounting for about 60%, and the A/S value is generally above 5.
(4) Characteristics of surrounding rocks and rock inclusions of ore bodies.
The bottom wall surrounding rock of bauxite body is Fe-Al claystone or Fe-Al claystone, and the top wall surrounding rock is dark gray or gray-white thin claystone, and there is no rock inclusion in bauxite layer.
4. Main achievements of the project
In the past, it was thought that after the formation of bauxite, due to structural changes, the aluminum-bearing rock series was lifted to the surface in the later period, subjected to long-term continuous weathering, scouring and leaching, and a large number of impurities such as high-silicon clay minerals and iron were lost, and aluminum was relatively enriched, forming soil-rich bauxite, and the A/S value gradually decreased to the deep. It is generally believed that there is no rich bauxite below 200 m.
Through the implementation of this project, it is found that there are still good bauxite-rich deposits in the deep part of Mianchi Lizhuangzhai mining area, such as ZK390 1, ZK31,ZK6304 and ZK5504, and the buried depth of bauxite deposits is180 ~ 298m. In ZK5504, bauxite with a thickness of about 17.36m is seen from 279 to 297 m, and the average ore content is: Al2O31.62%, SiO2 12.54%, with an average A/S value of 4.88 and the highest Al-Si ratio of 34. The thickness of ZK200 1 controlled bauxite in Yushan bauxite mine area of Xin 'an is 7.47m, the Al2O3 content is 75.03%, the SiO2 content is 4.80%, and the A/S value 15.63 ranges from 243.95 to 252.58m..
Bauxite and its roof and floor rocks are clayey rocks (mudstone) and belong to impermeable layers. The roof and floor of bauxite generally contain a lot of star-shaped or massive pyrite, such as ZK3 10 1 bauxite, with a sulfur thickness of 4.76m and a sulfur content of 12.76% ~ 16.44%. There is no desilication and desulfurization to make bauxite. The formation of rich bauxite is related to the sedimentary environment, but not necessarily to the present buried depth.
The breakthrough in the understanding of rich bauxite mineralization provides a theoretical basis for finding high-grade bauxite in the middle and deep part, which greatly expands the space and prospect of finding rich bauxite.
5. Bored core collection
ZK470 1 drilling, footage195.28m; ; ZK5504, with a penetration of 297.95m, is a bauxite with a thickness of about 17.36m from 279 to 297m, with an average content of Al2O31.62%, an average content of SiO2 12.54%, an average A/S value of 4.88 and the highest Al-Si ratio of 38. Borehole ZK470 1 passes through the II main ore body, and loess, glutenite, clay, glutenite, silty mudstone, sandstone, mudstone with coal seam, feldspathic sandstone, mudstone with coal seam, bioclastic limestone, mudstone, clayey rock and sandstone can be seen in the borehole. Coal seams are clay minerals, and the main mineral components are diaspore, kaolinite, iron chlorite, etc. The ore structure is mainly oolitic, clastic and aphanitic. The structure is mainly block, directional, layered and honeycomb. Bauxite ores are mainly clastic and oolitic bauxite, accounting for about 60%, and the A/S value is generally above 5. The bottom wall surrounding rock of bauxite body is Fe-Al claystone or Fe-Al claystone, and the top wall surrounding rock is dark gray or gray-white thin claystone, and there is no rock inclusion in bauxite layer.
ZK630 1, with a penetration of 92.55m and a hole depth of 78m, sees a layer of 6m oolitic bauxite, ZK630 1 passes through the main ore body II, and sees loess, conglomerate, sandstone, mudstone, timely sandstone, limestone, carbonaceous mudstone, siltstone, carbonaceous claystone and iron in the hole. The ore-bearing strata are iron-bearing bauxite and bauxite, and the ore minerals are mainly diaspore, hydromica and chlorite. The structure is mainly aphanitic and oolitic, and the structure is mainly dense and massive.
Drilling hole ZK6304, footage 212.56m, and geological conditions are the same as ZK630 1.
Because the surface of the mining area is thick loess, it is not easy to preserve, and the preservation significance is small. Therefore, the four cores collected this time have been reduced, that is, the surface loess has not been preserved.
The results of the above four boreholes are good, the core recovery rate meets the geological requirements and the ore content is good, which basically reflects the metallogenic geology of the mining area and the results of this bauxite evaluation project.
6. Relevant information
1) Map of Geology, Minerals and Work Deployment of Shanxian-Xin 'an-Jiyuan Area in Western Henan;
2) The topographic, geological and engineering distribution map of Mianchi lizhuang village;
3) borehole histograms of ZK4701,ZK5504, ZK630 1 and ZK6304;
4) Comprehensive profile of exploration line 47 in Lizhuangzhai mining area;
5) Comprehensive profile of exploration line 55 in Lizhuangzhai mining area;
6) Comprehensive profile of exploration line 63 in Lizhuangzhai mining area;
7)ZK470 1, ZK5504, ZK630 1 and ZK6304 sampling registration forms;
8) Geological records of ZK4701,ZK5504, ZK630 1 and ZK6304;
9) Brief introduction of Shanxian-Xin 'an-Jiyuan bauxite evaluation project.