Qushui: Originated in Liping County, Guizhou Province, it flows from south to north through Xianxi Town and Huitong in Jingxian County, and joins Qingshui River at Tuokou to form Shui Yuan, with a total length of more than 244 kilometers and a drainage area of 60 15 square kilometers. The upper reaches are deep valleys and Zhongshan area, with narrow rivers and undeveloped terraces. The middle reaches entered the Mesozoic red basin area of Jingxian County, where seven terraces developed. The downstream section of Huitong entered the canyon section again, and the longitudinal slope ratio decreased to 0.9‰.
Wuyang River: Originated in Luolang, huangping county, Guizhou, it flows northeast over Huaihua, flows through Shibing, Zhenyuan and Yuping in Guizhou, Xinhuang, Zhijiang and Huaihua in Hunan, and then suddenly turns south and flows into Shui Yuan, hongjiang city. The total length of the river is 422 kilometers, the drop is 420 meters, and the drainage area is 10366 square kilometers. Rivers are popular along the fault zone, and the longitudinal ratio of the south flow section is reduced to 0.89‰. In the suburbs of Zhijiang, there are five accumulation terraces in Quaternary.
Witch Water: Originated in the Jinlong Mountains at the junction of Hunan and Guangxi, it flows northward through Chengbu, Suining, Wang Jiaping, Gaoyi and Ruoshui, and flows into Shui Yuan in hongjiang city. The river is 227 kilometers long, with a total drop of 432 meters and a longitudinal slope of 1.9‰, which is steep and full of canyons. The basin covers an area of 4725 square kilometers. Rivers only develop in the terraced fields of Daizi Street and Suining.
Surabaya: It originates from the western slope of Xuefeng Mountain, flows through Luo Zhuang, Shuidong and Xupu, and flows into Shui Yuan at Dajiangkou, with a length of 142km, a drop of 578m, a longitudinal slope ratio of 3.66‰ and a drainage area of 3 184 km2, which is the smallest of the seven tributaries with the largest longitudinal slope ratio drop. There are many canyons in the upper reaches of Surabaya; The middle reaches enter the red rock hilly area with an altitude of 200~400 meters, and terraces are developed; There are many canyons downstream, and terraces are rarely preserved. The sixth terrace is mainly preserved in the areas of low village, Xupu and Dajiangkou.
Chenshui: Also known as Mayang River or Jinjiang, it originates from the eastern foot of Fan Jing in Guizhou Plateau, flows through Jiangkou, Tongren, Jinhe and Mayang, and flows into Shui Yuan in Chenxi, with a total length of 303 kilometers, a total drop of 390 meters, a vertical gradient of 1.29‰ and a drainage area of 6,834 square kilometers. Above Jinhe Town, Chenshui, it is mainly Paleozoic strata, mainly canyons. At the beginning of Yuan Dynasty, Jinhe Town entered the hilly area of Ma Hongyan, with flat terrain and meandering development, forming four to six terraces.
Dance Water: Originated in Dongguaao, Fenghuang County, it flows through Fenghuang, Hexi and Xixi, and flows into Shui Yuan at Luxi. The Wushui River above the river is called Tuojiang River, with a total length of 170km, a total drop of 500m, a longitudinal slope of 2.94‰ and a drainage area of 39 12k m2, which is only slightly larger than that of Xu Shui among the seven tributaries.
Youshui: It is the largest tributary of Yuanshui, originating from the border of Hunan, Hubei, Chongqing and Guizhou, flowing through Longshan, Shidi, Baojing, Luoyixi and Wusu, and pouring into Yuanshui in Yuanling, with a total length of 432km, a total drop of 4 10/0m and a longitudinal slope of 0.95‰. Above Luoyixi in Guzhang, it is the birthplace of Youshui, Yunnan, Guizhou, Chongqing, Hubei and Wuling blocks, and the strata are mainly carbonate rocks. After crossing Luoyi West, it passes through Guzhang anticline (Qingbaikou stratum), enters Yuanhahong Basin and flows into Yuanshui River. There are many rapids and rapids, and there are 54 rapids in the whole basin. Terraces are underdeveloped, and only a few areas such as Longshan, Liye, Huayuan, Baojing and Yongshun have one to seven terraces. It should be mentioned that although the suburb of Longshan is not far from the source, due to the circuitous river and wide valley, the terrace area is not less than 80 square kilometers, and the Quaternary preservation area is not less than 40 square kilometers, showing five terraces. See Table 4- 1 for terrace elements in seven tributaries.
Table 4- 1 List of terrace elements of seven tributaries of Yuanshui River
sequential
4.2.2 Enrichment law of diamonds and placers in the tributary of Yuanshui River
Qushui: In the 1950s and 1960s, in order to find near-source sand-rich mines and trace back to the original mining areas, large-volume placer mines were successively investigated in Gao Yong Lianshan, Jingxian suburb, Tongdao Qingwuzhou, Jingxian Xinchang, Outuan, Kangtouzhai and Gongdongxi, and diamonds were found, but the content was very low, with an average of 65,438 diamonds of 270 cubic meters. The strata in Outuan area belong to Nanhua system, and no rock mass and diamond indicator minerals have been found after detailed investigation. There is a peculiar layer of gravel in the Huopo lowland of Kangtouzhai, which is 800 meters above sea level. Therefore, the source of diamonds in this area has not been identified.
Wuyang River: In 1950s, in Qiancheng (now hongjiang city), Hongyan Mountain, Zhong Fang and Zhijiang, the aircraft investigated placer deposits and found 26 diamonds. However, no diamond was found in Yuping, Guizhou Province, and 1 diamond was found in the convenient water division of Zhijiang and Xinhuang County. In the heavy sand investigation of regional water system, purple series garnet is only seen in major rivers. The main strata of Wuyang River in Hunan Province are Neoproterozoic Qingbaikou system and Cretaceous red bed, followed by Sinian system and Cambrian system. The middle and upper reaches of Wuyang River mainly pass through the Hunan-Guizhou fault, and no diamond enrichment points were found in the placer survey in the middle and lower reaches.
Wushui: According to the general survey of diamond placer in 1950s and 1960s, only 1 ~ 2 diamonds were found in the middle and lower reaches and their tributaries, such as Palm Tree Foot, Tuanhe Wayao, Wang Jiaping and Hongjiangdai Street, and only 1 diamond was found in each point, with an average sampling of 200 cubic meters, and no sand-rich ore was found. The strata in this basin are mainly Nanhua system, followed by Qingbaikou system and Sinian system.
Surabaya: The Quaternary system developed in Xupu suburb, with a large distribution area. In the 20th century, 728 cubic meters of mineral processing samples were taken, and only 1 fine diamond was seen. 1 fine diamond was found in Luo Zhuang during the heavy sand survey of regional water system. Anomaly of chromite spinel was found in Liangyaping containing chromite, but its source was not found. The main strata in the basin are Qingbaikou Formation, Nanhua Formation, Sinian, Cambrian, Cretaceous and Paleogene. The NE-trending Xiang-Gui lithospheric fault runs through the basin. Lamprophyres appear in groups and belts in Shibadu and Majia areas.
Chenshui: During the period of 1958, 682.5 cubic meters of mineral processing samples were taken from Jinhe Town, Mayang County, and 768.5 cubic meters were taken from the suburbs of jiangkou county, Guizhou Province. No diamonds were found.
Wushui: In the 1970s, in the general survey of heavy sand sampling in regional water system, 56 diamonds with placer gold were found in karst sediments and water system at an altitude of 720m in the distribution area of Cambrian limestone in the Yellow River, but no diamond indicator minerals were found. However, four kinds of garnet crystals were found in artificial heavy sand samples taken from bamboo limestone. Two diamonds were found in the water system in this area.
Youshui: In the 20th century, diamond placers were surveyed in Luoyixi, Huayuan, Baojing, Liye and Longshan suburbs of Guzhang County, and no diamonds were found. Only at the entrance of Youshui into Shui Yuan, three tiny diamonds were found in Baiyangping IV stage. Whether it comes from Shui Yuan or Youshui is controversial. 1 garnet was found in Zejiahu, Yongshun County and Fuxingchang, Baojing County, respectively. The middle and upper reaches of Youshui River are distributed in Wuling fault block area, and the cutting strata are mainly Paleozoic carbonate rocks. The NE-trending lithospheric fault under the crust of Hubei, Hunan and Guizhou passes through the Youshui Basin.
Table 4-2 Statistics of Diamond Characteristics of Seven Branches of Yuanshui River
sequential
* Diamond was found in heavy sand sampling.
4.2.3 Diamond Characteristics in Yuanshui River Basin
According to the classification of jewelry, colorless and transparent diamonds in meta-aquatic products, that is, water-purifying diamonds (American standard class I), account for about 4.5%; The surface is light yellow and light brown, and the interior is transparent (AGS standard ⅰ ~ ⅱ), accounting for about 68%; The surface is light yellow, light brown and other colors, and the interior is silvery white (AGS standard ⅱ), accounting for about17%; Diamonds below Grade II account for about 10.5%. About 80% of the diamonds produced in Hui Yuan are gem-grade, with strong diamond luster. British mineralogist Harris said, "I have never seen a diamond with such a strong luster." Most diamonds in Shui Yuan are Brazilian dodecahedron single crystals, accounting for about 87%. Octahedral single crystal accounts for about 8%; The rest are cubic, tetrahedral and octahedral polycrystals. The integrity rate of crystal face and crystal edge of single crystal reaches 85%. The largest diamond found in Shui Yuan weighs 70 carats and was produced in the port of Taoyuan County. According to the existing statistics, among Shui Yuan diamonds, 0. 1~0.25 carats account for 38.7%, those larger than 0.25 carats account for 19.8%, and the rest are 0.025~0. 1 carat. The quality of diamonds in Shui Yuan is better than that in Brazil. Dingjiagang and Taoyuan mining areas are large and medium-sized gem-grade diamond sand deposits.