Value of geosites

2018-04-11

Jiuhuashan is featured by towering, beautiful, complicated and diverse composite rock body and the integrated landscape combining the northern subtropical vegetation with Buddhist culture, and as an outstanding model of large scale fault-block granitic landform and unique fluid-rich granite crystalline structure cave which present the sima to sial molten magmatic activities and late tectonic activities in deep crust during the collision between Eurasian Plate and Pacific Plate. These are reasons for applying Jiuhuashan Geopark for the membership of UNESCO Global Geopark.

The geosites of Jiuhuashan Geopark are classified into 3 sites of the world-level, 9 sites of the national-level, 9 sites of the provincial-level, and 10 ones of the local-level in accordance with their values in science, science popularization and aesthetics as well as natural and cultural systematicness and their relationship with geology.

The composite rock body and large scale fault-block granite landform of Jiuhuashan are of the global significance. It is an ideal place for scientific research, teaching and science popularization of granite geology and the related field.

(1) Geosites of Jiuhuashan Geopark are representatives of magmatic activity in the collision between oceanic and continental plates in East Asia. The fluorine-rich geode granite and bimodal magmatic activity in the Geopark are good cases for research on crystallization differentiation process of fluid-rich magma and the crust-mantle magmatic interaction.

a. Records of magmatic activities in collision between the Pacific Plate and the Eurasian Plate. The total area of Jiuhuashan composite granite rock body is 790 km2. It is the largest Yanshanian composite granite rock body in the lower Yangtze region and as one of the compositions of the granite belt in the western coast of the Pacific Ocean. The main rock body was formed by two magmatic activities with a shape of concentric telescoped intrusion as a whole. These two magmatic activities occurred respectively at 141-145 Ma and 121-130 Ma ago. The earlier-formed rocks are I-type granodiorite and monzonitic granite, they are mainly distributed in the periphery of the rock body in a larger scale. Both of them are consistent with the same rock type in South China in terms of formation age, and are closely related with the westward subduction of the Pacific Plate. The later-formed rocks mainly are the alkali A-type geode granite, basic veins and alkaline granite porphyry veins. Alkali granite is the main rock type of Jiuhuashan Geopark and the rock is in light incarnate red and medium-fine grain structure. The main rock-forming minerals include alkali feldspar, plagioclase, quartz and few biotite. They widely developed geode structures among the rocks, which indicates that the magma intrusion is located in shallow underground near the earth surface and rich in volatile components. The alkali granite, basic veins and alkali granite porphyry of Jiuhuashan have a close relationship in terms of genesis type, indicating the extension environment after the subduction of the Pacific Plate.

b. A representative of bimodal magmatic activity. The bimodal magmatic activity is usually considered to be closely related with a tensional structure, which was formed in continental rift or back-arc region. Among them, the mafic rock is considered to be the product of melting part of mantle. The bimodal igneous rock association of Jiuhuashan is presented in late mafic veins and the felsic A-type syenogranite. Zircon U-Pb chronology research shows that mafic magmatite and syenogranite are the products of contemporaries (around 125 Ma). The symbiosis of contemporaneous alkali granite and mafic dyke here is a representative of bimodal magmatic activity, indicating a relatively deep magma source area and reflecting the mixing process of crust-mantle magma.

c. A good case area for research on crystallization differentiation of fluid-rich granite magma. Geode structure is well developed in the alkali granite of the Jiuhuashan with automorphic quartz, feldspar and purple and green fluorite single-minerals (F-rich minerals) crystallized in the geode. Chemical composition analysis of minerals found that the biotite of alkali granite at Jiuhuashan has more F-rich elements than other rock types, indicating that there is rich fluid in the alkali A-type granite of the Jiuhuashan. In addition, alkali granite has more silicon, potassium, sodium but fewer elements of magnesium, iron, titanium, calcium and phosphorus than the paragenetic granodiorite and monzonitic granite, indicating that the alkali magma has a higher evolution degree. Geode structure commonly developed in the alkali granite, indicating that it is more enriched in fluid and volatiles, and the depth of emplacement is shallower and closer to earth surface.

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Jiuhuashan rock body (syenogranite)

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Qingyang rock body (granodiorite)

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Miarolitic granite

(2)Jiuhuashan Geopark is a prototype of large fault-block granite landform, and the geomorphic combination of "mountain-hill-basin" shapes the biodiversity and civilization of Jiuhuashan.

a. Jiuhuashan is a prototype of large scale fault-block granite landform, and also is a model of natural beauty and the developmental mechanism of granite landscape.

Jiuhuashan fault block sharply rises to 1,300 m from hilly area with elevation of no more than 300 m above the sea level, extending about 30 km in north-south direction, displaying the magnificent appearance and development mechanism of this fault-block. There are 71 peaks with various sizes at Jiuhuashan Shiwang Peak, being the highest one with an elevation of 1,344.4 m. In addition, the height of Lotus Peak and the Lion Peak also exceeds a thousand meters and extends in north-south direction. Many peaks are in shapes of cone (Tianzhu Peak), column (Candle Peak), ridge (Shiwang Peak), dome (Tianhua Peak), box-like (Shamao Peak) and form the essence of Jiuhuashan geology and landform.

Granitic peaks of Jiuhuashan Geopark are characterized by odd shapes and of great aesthetic value. They perfectly display the shape-developing mechanism by geological processes. Firstly the special bimodal igneous rocks are good materials, and secondly the joint undercutting of Jiuhuashan Fault and many associated small joints are strong and suitable structural conditions with agents of flowing water and freeze-thaw, divers and beautiful peaks developed in Jiuhuashan granitic mountain such as grotesquely-shaped rocks at Huatai and Tiantai. With a combination of diverse natural vegetations, changing and delightful climate, nice environment and rich resource, special water source, was the fantastic landscape born in Jiuhuashan granitic mountain and a natural basis of the Jiuhuashan’s cultural landscape come into being. All of these are powerful impetus for geosite protection.

b. The fault-block granite landform of mountain-hill-basin shapes biodiversity and the civilization of Jiuhuashan. Being controlled by Jiuhuashan Fault, the upthrown block was lifted to create the Jiuhuashan large fault-block granitic mountains extending over 30 km in north-south direction and with average elevation of 1,000 m, and the downthrown block descended down to form hills with average elevation of 270 m and basins with average elevation of 30 m, which comprise a magnificent landscape of “mountain-hill- basin” just in a straight-line distance no more than 6 km. The such towering granitic mountain landscape are not only a geomorphic pattern but also divers habitats of animals and plants. And moreover, the granitic mountain platform provides the sites for the construction of Jiuhuashan Buddhist architecture and Hui-style architecture. The grotesquely-shaped granite rocks, such as The Goddess of Mercy Viewing the land of Buddha, the Buddha View the Sea, were given a new connotation of Buddhist culture. The basins and hills provide a wide space for production and living of local residents and monks in Jiuhuashan Community. All of the above have promoted and continue to promote development of the Jiuhuashan civilization.

c. Jiuhuashan is a Buddhist ashram resort that records real people, real event and real record on the basis of this typical granitic mountain of China. "Real people" refers to a prince of Silla (Korea), Kim Gyo-gak in A.D. 719; "real event" refers to the prince cultivated himself at Jiuhuashan for 75 years and passed away here; "real record" means the death of the incorruptible human body as the sacred site of Ksitigarbha. The combination of mountain-forest-water at Jiuhuashan provided an environment with features of "magnificent, beautiful, moist and tranquil" for Buddhism ashram. "Magnificent" refers to the 1,000 height difference in an area within a distance of 6 km and peaks extends about 30 km in north-south direction; “beautiful” refers to the dense forest at these mountain peaks with elevation range of 1,000m; “moist” refers to abundant rainfall, mild climate, and flowing streams that are the basis of all living things; “tranquil” refers to a tranquil environment featured by dense forest and flowing stream, although here is not far away from the busy waterway of Yangtze River.

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Mountain-hill- basin geomorphologic landscape

(3) The Quaternary glacier relics of Jiuhuashan are important records of the Quaternary glaciers in the eastern China.

During the Cenozoic Era, multiple cold climate events occurred in the world and large-scale glacier activities happened. After having visited Lushan, Huangshan, Tianmushan, and Jiuhuashan in 1930s, Prof. Li Siguang, a famous Chinese geologist pointed out there were glacier relics in the Jiuhuashan, including Jiuhua Street cirque, the U-shaped valley of Jiuhua Street - large/small bridge nunneries, and terminal moraine ridge.

According to the Anqing’s regional geological survey map with a scale of 1:200,000, Machong Formation, a boulder clay layers formed by glacial fluvial deposit of the Pleistocene have been found near Ducun Bridge about 5 km away in the northwest of the Jiuhuashan Geopark. Gravels of the layer are not well-rounded, most of them are angular, flat-topped, different from the shape of fluvial or pluvial pebbles. Thus, they were considered to be formed by glacial deposit.

However, some scholars considered that there were no geological conditions for glacier at Huangshan or Jiuhuashan. The academic debate, just like the glacial relics of the eastern China, would drive the geoscience research. We believe the protection of geosites in Jiuhuashan Geopark, including the Quaternary glacial relics, is of great scientific value for paleoclimate and environmental evolution in the region.

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Jiuhua cirque

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Minyuan glacial erratic boulder


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