The common siliceous rocks in Guangxi are massive, banded and layered structures. Petrochemistry shows (Table 5- 1, Table 5-2) that the SiO2 _ 2 content of massive siliceous rocks is relatively high, generally above 85% ~ 90%, and the highest can reach 97.2 1%. Secondly, the content of Fe and Mn is higher, especially the content of MnO is relatively high, generally 0. 13% ~ 0.35%, while the content of TiO2, Al2O3, MgO and CaO is lower. For banded siliceous rocks, the chemical composition of banded siliceous rocks is complicated by adding other components besides banded and banded siliceous rocks, such as argillaceous, manganese carbonate, other carbonate rocks, siliceous limestone, iron and carbon. First of all, the content of silicon dioxide is reduced, generally less than 75%, and the lowest is only about 45%.
Among the major elements, MgO content is an important index to judge whether the deposit is a hot water deposit. In the modern mid-ocean ridge hot water system, MgO is a component with serious loss, and the content of MgO in the mid-ocean ridge hot water in the eastern Pacific Ocean at 350℃ is zero, so the increase of magnesium in the hot water system can be used as an indicator of seawater pollution and mixing (Edmond et al., 1983). The content of MgO in massive siliceous rocks in Gaolong mining area and massive or striped siliceous rocks in Gutan mining area is very low, while that in Gaolong gold mine is trace, and that in Gutan mining area is less than 0.05%, and its ratio of SiO _ 2/MgO is more than 2000. The content of MgO in other banded siliceous rocks is increased due to carbonate composition in banded or dolomite surrounding rocks, generally ranging from 0.25% to 65438 0.27%, and a few are close to 4%. It can be seen that the formation of these siliceous rocks in this area is related to the action of hot water.
The results show that the enrichment of iron and manganese in marine sediments is mainly related to the participation of hot water, while the enrichment of aluminum and titanium is related to the participation of terrigenous substances (Bostrom et al., 1969,1973; Zuli,1986; Yamamoto, 1987). Therefore, Bostrom et al. (1969, 1973) put forward the ratio of Al/(Al+Fe+Mn) in marine sediments as an index to judge the participation of hot water components in sedimentation, and this ratio decreased with the increase of hot water sediment content in sediments. Zuli et al. (1986) and Yamamoto (1987) pointed out that the Al/(Al+Fe+Mn) ratio of siliceous rocks ranges from 0.0 1 of pure hot water sediments to 0.60 of offshore biogenesis. Turekian et al. (196 1) research shows that the ratio of modern deep-sea pelagic clay is 0.54, that of offshore clay on shelf is 0.6 13, and the corresponding average ratio in shale is 0.62. Sugizaki et al. (1982) and Yamamoto et al. (1983) pointed out that the ratio of radiolarian flint rocks in China and Japanese coastal areas is 0.6; Relevant research shows that this ratio of hot water sediments is very low, such as that of hot water sediments in the East Pacific uplift is lower than 0.0 1(Bostrom et al., 1969), and that of SiO2 _ 2 sediments near siliceous vents in the Galapagos Rift is close to zero (Herzig et al., 1988).
Table 5- 1 Petrochemical Composition and Parameters of Siliceous Rocks in Guangxi
Note: A-SRO; B treasure; C-TFe2O3. Sample testing unit of this book: Guilin Nonferrous Metals Mineral Geology Testing Center.
Table 5-2 Petrochemical Composition and Parameters of Siliceous Rock
Fig. 5- 1 diagrams of Fe/Ti and Al/(Al+Fe+Mn) of siliceous rocks in Guangxi
The relationship between Fe/Ti and Al/(Al+Fe+Mn) is an index to judge whether a modern submarine metallic hydrothermal deposit is a hydrothermal deposit according to its geochemical characteristics. Bostrom( 1983) pointed out that a marine deposit is a typical hot water deposit when its Fe/Ti is more than 20 and Al/(Al+Fe+Mn) is less than 0.35. In 1973, the Fe/Ti-Al/(Al+Fe+Mn) diagram is drawn to distinguish hydrothermal metal deposits in deep-sea sediments. Later, Bostrom( 1983) and Spry( 1990) further drew up the diagram of Fe/Ti- to distinguish the mixing ratio of hot water sources and terrestrial materials.
The Al/(Al+Fe+Mn) ratio of siliceous rocks in this area is shown in table 5- 1 and table 5-2. It can be seen from Table 5- 1 that among the samples of 16 from five mining areas in Guangxi, the ratio of 1 1 sample in four mining areas (Panlong, Gutan, Xia Lei and Gao Long) is less than 0.35, which indicates that it is typical hot water. However, it is still close to the value of 0.35. At the same time, all four rock samples belong to banded or lamellar siliceous rocks. In addition to siliceous bands, rocks also contain argillaceous limestone or calcareous mudstone bands, which increase the aluminum content and Al/(Al+Fe+Mn) ratio. Obviously, pure siliceous zone is a typical hot water deposit, and banded siliceous rocks are also the products of hot water deposit, which only shows that certain terrigenous materials were deposited during the intermittent period of hot water deposit to form this zone. The only sample whose ratio (0.59) is close to 0.6 belongs to the eighth layer of the lower manganese ore area, that is, the siliceous rock on the roof of the ore body, which is the product of hydrothermal deposition and mineralization in the later period. It should be normal that more terrigenous detrital materials are involved, which makes its ratio higher. In addition, from the average value of Al/(Al+Fe+Mn) of siliceous rock samples collected from eight places in Dachang, Gui Mu and Debao, Guangxi (Table 5-2), the ratio of six places (Panlong, Gutan, Xia Lei, Gao Long, Gui Mu and Debao) is less than 0.35, as mentioned above. The ratio of the other two places (Chatun and Dachang) is 0.39, which is also close to 0.35, indicating that it is mainly the product of hydrothermal deposition. For example, the ratio of siliceous rocks in Dachang is 0.39, which may be related to the fact that some siliceous rocks are banded siliceous rocks, that is, besides siliceous rocks, there are some bands composed of argillaceous rocks or feldspar and sericite (Han Fa et al., 1997).
Comparing the Al/(Al+Fe+Mn) ratio of siliceous rocks in these areas of Guangxi with the Al/(Al+Fe+Mn) ratio of siliceous rocks at home and abroad (Table 5-2), it can be seen that it is compared with the Al/(Al) ratio of hydrothermal sedimentary siliceous rocks in Bafangshan, Qiandongshan, Dengjiashan, Bijiashan and Barrow lead-zinc deposits and Laerma gold-uranium deposits in Qinling area of China and Mojiang gold deposit in Yunnan. Song Chunhui et al.,1992; Liu Jiajun et al.,1993; Ying Hanlong et al.,1999); The Al/(Al+Fe+Mn) ratio of hydrothermal sedimentary siliceous rocks in Chuande lead-zinc deposit in North Korea is also very similar, which is similar to the Al/(Al+Fe+Mn) ratio of hydrothermal sedimentary siliceous rocks in Fran-ciscam terrane of the United States and siliceous rocks such as hydrothermal siliceous rocks and white clay in the 32nd voyage of deep-sea drilling plan, but obviously similar to radiolarian siliceous rocks in Kamiaso, China. However, some mining areas do have terrigenous materials mixed in, often forming banded siliceous rocks with calcareous mudstone bands. This feature is very similar to the flint rock of the Yuchuan manganese mine in Tianye. The flint rocks in Tianye Yuchuan mining area are considered to be formed by submarine hot springs, and its Al/(Al+Fe+Mn) ratio is 0.55. The reason may be that there are more thin layers of flint in Al2O3. As mentioned above, the enrichment of titanium and aluminum in marine sediments is related to the participation of terrestrial materials. Therefore, some thin layers of thin-layer flint in the mining area may be mainly terrigenous materials, which increases the Al content in the rock and leads to the increase of Al/(Al+Fe+Mn) ratio. Xia Lei and Chatun in Guangxi are also manganese ore areas, with similar ore bodies, ore compositions and siliceous rocks, and high Al/(Al+Fe+Mn) ratio (Table 5- 1). Compared with them, it also shows that siliceous rocks in this area are mainly caused by hot water deposition.
On the Fe/Ti-Al/(Al+Fe+Mn) diagram (Figure 5- 1), the samples from various mining areas in Guangxi are mainly concentrated in the middle of the curve, and the proportion of hot water sources is about 40%, of which two thirds are about 50% and one third is more than 60%, which is consistent with the above characteristics.
According to the different sources of iron, manganese, aluminum and titanium in marine sediments, Bostrom et al. (1969) also drew an Al-Fe-Mn triangle genetic discrimination diagram to distinguish hot water sediments from normal sediments. Later, Zuli et al. (1986) and Yamamoto (1987) also successfully applied this figure (Figure 5-2) to the genetic discrimination of siliceous rocks. At the projection point of 16 siliceous rock samples from five mining areas in this area on the Al-Fe-Mn ternary diagram, only the siliceous rock samples from the roof of Xia Lei mining area fall into the non-hot water area, the other five samples fall into the transition zone between hot water deposition and non-hot water deposition, which is the product of the interaction between hot water deposition and terrigenous water deposition, and the remaining 10 samples all fall into the hot water deposition area. The projection points of the average value of siliceous rocks in other Dachang, Gui Mu and Debao areas show that only Dachang belongs to the transitional zone between hot water deposition and non-hot water deposition, while both Gui Mu and Debao areas belong to the hot water deposition zone. These are consistent with the above understanding, reflecting that siliceous rocks in Guangxi are mainly the products of hydrothermal deposition, and some mining areas are involved in terrigenous materials.
Figure 5-2 Al-Fe-Mn Triangle Diagram of Siliceous Rock (according to Zuli et al. 1986)
Second, the characteristics of major elements in barite rocks
See Table 5-3 for the petrochemical analysis results of barite from Jilongding copper-silver polymetallic mine, Laibin Gutan barite mine, Wuxuan Panlong lead-zinc mine and Sanjiang barite mine in Rongxian, Guangxi. As can be seen from the table, the chemical composition of barite rocks in four mining areas in the area is relatively pure. Except for one sample from Panlong mining area, the BaSO4 content of other samples is about 97%, and only the SiO2 _ 2 of Gutan and Sanjiang and the SrO of Panlong are in the range of 1% ~ 2%, and the other components are less than 1%. This feature is very similar to that of barite rocks in Xinhuang, Hunan, Suizhou, Hubei and Yindongzi, Shaanxi, and is considered to be formed by hydrothermal deposition (Tu Guangchi et al.,1987; Yan, 1995), so it is speculated that the above four barite rocks in this area may also be related to hydrothermal sedimentation. In addition, the Fe2O3 content of barite samples in this area is higher than FeO, indicating that the formation environment is relatively oxidized.
Table 5-3 Petrochemical Composition and Parameters of Barite
* TFe2o3； The figures in brackets are calculated values; Source: 1~9 books; 10 N 12 Tu Guangchi et al. (1987); 13 strict (1995). The sample testing unit of this book: Guilin Nonferrous Metals Mineral Geology Testing Center.
As mentioned above, the ratio of MgO to Al/(Al+Fe+Mn) in marine sediments is an important index to judge whether marine sediments are hot water deposits, and whether the sediments are hot water deposits can be effectively judged by using the Al-Fe-Mn triangle genetic discriminant diagram. Because barite rocks in four places in this area are all marine sediments, these indicators and diagrams can also be used to discuss their genesis.
Characteristics of MgO content: the MgO content in the barite sample of 10 in this area is very low, and the MgO content in Sanjiang sample is 0.05%; The MgO content of 1 sample in Panlong mining area is 0.35%, and that of 1 sample is 0.0079%. The MgO content of the other seven barite rocks is less than 0.05%. This is consistent with the serious loss of MgO in the modern mid-ocean ridge hot water system (Edmond et al., 1983), and similar to the low MgO content in barite rocks deposited by hot water in Xinhuang, Suixian and Yindongzi (Table 5-3). It can be considered that the formation of barite rocks in these mining areas is related to the action of hot water.
Al/(Al+Fe+Mn) ratio: As can be seen from Table 5-3 and Figure 5-3, the Al/(Al+Fe+Mn) ratio of eight barite samples from four mining areas in Guangxi is 0.02 ~ 0. 19, which is obviously less than 0.35, and it is a typical hot water deposit. The Al/(Al+Fe+Mn) ratios of the other two samples are 0.5 1 and 0.53, respectively, which is less than 0.6, indicating that hot water still exists, because both samples belong to Gutan mining area and have striped or banded structures, while the other sample, which is also a mining area, is dense and massive, with a low ratio of 0. 19. From the whole mining area, combined with the analysis of the characteristics of siliceous rocks in the above mining area, barite rocks in Gutan mining area should be mainly the product of hot water. Comparing the Al/(Al+Fe+Mn) ratios of barite rocks from four mining areas in Guangxi with those from Xinhuang, Suixian and Yindongzi mining areas in China, we can also see that the ratios are similar, which are mainly typical products of hydrothermal deposition.
On the genetic discrimination diagram of Al-Fe-Mn Triangle (Figure 5-4), eight barite samples from four mining areas in Guangxi 10, and the projection points of barite samples from three mining areas in Xinhuang, Suixian and Yindongzi of China all fell into the hot water deposition area, and only two barite samples from the ancient beach fell into the non-hot water area. These two samples (Gu 3 and Shen 4) are the above tools.
Fig. 5-3 diagrams of Fe/Ti and Al/(Al+Fe+Mn) of barite rocks in Guangxi (the original diagram is based on Spry, 1990, and the description in the diagram is the same as that in fig. 5- 1).
Figure 5-4 Guangxi Barite Al-Fe-Mn Triangle Diagram (according to Zuli et al. 1986)
Three. Characteristics of constant elements in electrical rocks
Because the mineral components in calcium carbide (or electric Shi Ying) except tourmaline are mainly chronotropic, and its chronotropic content can reach 40% ~ 70%, calcium carbide can be regarded as a special siliceous rock. See Table 5-4 for the chemical composition analysis results of hydrothermal sedimentary mantle rocks in Guangxi and some areas at home and abroad. As can be seen from the table, the contents of major elements in calcium carbide in these areas are almost the same, especially the content of SiO2 is higher, generally more than 60%. The content of silica in calcium carbide rocks in Yidong area of Guangxi is 62.35% ~ 76.74%, with an average of 67.67%, and the content of silica in calcium carbide rocks in Dachangpo-Tongkeng area is 66.59%, both of which are close. Therefore, pyroxenite can be regarded as a special siliceous rock in terms of mineral composition and chemical composition. The content of other elements in rocks is characterized by high Al2O3 content. The Al2O3 content in a rock cave in Shi Ying electric power plant ranges from 9.12% to13.76%, with an average value of 12.48%, which is slightly lower in Dachangpo-Tongkeng mining area, reaching 6.33%. In addition, the high content of FeO, Fe2O3, MgO and B2O3 in rocks is also an important feature of rocks, especially B2O3 content, which is as high as 2.96% ~ 4.32% in Yidong mining area, with an average of 3.85%, except that it is slightly lower than 0.7 1% in Dachang mining area.
Han Fa et al. (1989) and et al. (1990) proposed that biogenic siliceous rocks can be effectively distinguished from volcanic or submarine hydrothermal siliceous rocks by using the correlation binary diagram of the contents of TiO _ 2, Al _ 2O _ 3, K _ 2O and Na _ 2O in siliceous rocks. On the binary diagram of Al _ 2O _ 3-TiO _ 2 and Al _ 2O-(K _ 2O+Na _ 2O), it is judged that the electric quartzite (electric quartzite) is a special kind of siliceous rock. It also shows that the projection points of the electric quartzite in a cave in Guangxi and the electric quartzite in Changpo-Tongkeng, as well as those in other mining areas at home and abroad, are all deposited with siliceous rocks in the volcanic arc area and submarine hot brine. In particular, the author also found that on the binary diagrams of Al2O3-TiO2 _ 2 and Al2O3-(K2O+Na2O), silicalite and pyroxenite from different sources have their own obvious enrichment areas. In the hot water sedimentary area, the projection points of these pyroxenites are closer and relatively concentrated in a small area, so it is called the hot water sedimentary pyroxenite area, that is, HT area. Whether from Hujiayu copper mine in Zhongtiaoshan, Bailuwutu copper-sulfur polymetallic mine in Inner Mongolia and Zhangjiagou-Caijiagou pyrite mine in Liaodong, or from Sullivan lead-zinc-silver mine in Canada, Brokenshire lead-zinc mine in Australia and Gordon Dekedom lead-zinc gold mine abroad, these rocks are considered as typical hydrothermal sedimentary rocks (Sun Haitian et al.,1990; Nie Fengjun et al.,1990; Xia,1997; Han Fa et al.,1997; Slack， 1993； Plimer, 1986), from the petrochemical point of view, provides new evidence for the hydrothermal sedimentary genesis of Yingdianying rock and Dachangpo-Tongkengdian rock in Guangxi. At the same time, it also provides a new genetic discrimination diagram for the genetic interpretation of hydrothermal sedimentary calcium carbide.
Four. Characteristics of major elements in layered skarn
Layered skarn occurs in Fozichong lead-zinc mine in Guangxi, Tao Dong lead-zinc mine, Niutangjie tungsten mine and Qinjia copper-tin mine, and is the direct host rock of the deposit. For the characteristics of major elements of layered skarn, predecessors have studied it with Al/(Al+Fe+Mn) ratio and Fe/Ti-Al/(Al+Fe+Mn) diagram, such as the study of layered skarn in Yangla copper concentration area in northwest Yunnan by Lu Yuanfa (1999) and Liu Yuping (1999). Yang Bin et al. (2000a) studied the layered skarn in Fozichong lead-zinc ore field, and the results of * * showed that the ratio of Al/(Al+Fe+Mn) was 0.033 ~ 0.39, with an average value of 0.203, which was a typical hot water deposit. On the Fe/Ti-Al/(Al+Fe+Mn) diagram (Figure 5-7), most of the projection points are located near the throwing point of Haiyuan hot water sediments, and some projection points are close to the end members of terrigenous sediments, indicating that some terrigenous materials are involved. The author studied, analyzed and tested two skarn samples in Tao Dong mining area. The Fe/Ti ratios are 163.28 and 13.08, with an average of 88. 18, and the Al/(Al+Fe+Mn) ratios are 0.06 and 0.53, with an average of 0.295, which are typical hot water deposits. On the Fe/Ti-Al(Al+Fe+Mn) diagram (Figure 5-7), one projection point falls near Haiyuan hydrothermal deposit, and the other projection point falls near terrigenous deposit endmember, showing obvious interference characteristics of terrigenous substances. Therefore, the research results generally show that the layered skarns in Fozichong and Tao Dong lead-zinc mine areas are mainly the products of hydrothermal deposition, but there are also some terrigenous materials involved.
Table 5-4 Petrochemical Composition Percentage of Dianyingyan (Dianyingyan)
Note: The sample testing unit of this book: Guilin Nonferrous Metals Mineral Geology Testing Center.
Fig. 5-5 Diagram of Al2O3-(K2O+Na2O) of siliceous rocks with different genetic types (the original diagram is based on Mao Jingwen et al., 1990).
Fig. 5-6 TiO _ 2-Al _ 2O _ 3 diagram of siliceous rocks with different genetic types
(The original picture is based on Mao Jingwen et al., 1990). The legend is the same as Figure 5-5.
Fig. 5-7 Fe/Ti-Al/(Al+Fe+Mn) diagram of layered skarn (according to BostromK. , 1973).