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Poster Session
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On the genetic model of The Fenhe-Weihe Rift
Yan Xinmin and Bai Xinfeng
Remote Sensing Center of Shaanxi Province, Xian, China
Abstract
The Fenhe-weihe Rift, one of the typical epigenotypes of continental rifts in China, is located the middle east region of the conjunction part between the two great-circle tectonic belts in the Northern Shaanxi and in Shangyun-Bashan area. The satellite picture shows that the north margin and the south margin of the rift can be matched. In the rift, the curie isothermal plane reflects a very peculiar regional distribution of the Weihe rift which are reflected by gravity-magnetic field, water system, crustal strees, geothermals, neotectonic movement and undulatory Moho etc. according to the properties mentioned above, a new recognition of the Fenhe-Weihe Rift was proposed in the paper. Thus a new model of formation and evolution of the Fenhe-weihe rift was established. The rift was formed by the crustal extension caused by the mantle upwaring mainly in the areas of Weinan, Linfen, Jingning and Hanzhong, and by counter clockwise rotation of the rock mass in the North Shaanxi great-circle tectonic and clockwise rotation of the rock mass in the Shangyun Bashan great-circle tectonic caused by the mantle upwarping.
The feature of The Fenhe-Weihe Rift
- Geological and Geomorphologic Feature
The Fenhe-Weihe Rift is situated at the southern part between Shanxi up warping region and the Jishaan fault valleys in font of the estern Qinlin mountain . It has the largest area and the deepest depth in the valleys. From Baoji in Shaanxi province to Huoxian in Shanxi province, the land form looks like a crescent graben basin, extended southeast six hundred kilometres in length, and ninety kilometers in width, and measures four thousand square kilometers [1] . The average height is about two thousand metres about the Qinling and Huoshan mountain in southeast, and nine hundred to thirteen hundred metres about the Beishan and Luliangshan mountains in northwest. The vast and flat Fenwei plain between them is about four hundred metres high and is a down-warped basin filled with thicker and looser sediments. The Weihe Rive and the Fenhe River flow into the centre of this basin from west and north separately. Some sub-basin and sub-swells are distributed alternately in this basin.
- satellite Images Feature
We interpreted the main faults in the Fenhe-weihe Rift and its neighbourhood from the satellite images and other aerial remote sensing data in this area (see appendix 1), some direct and eye-catching information was discovered as follows:
- There are two circular structures that correspond to the northern Shaanxi roke mass(I) and the Shangyunbashan roke mass (II) [2] in addition, the Yikezhaomeng roke mass (III) also showsup obviously. The northern shanxi roke mass is on the north of the Qinling mountain and south of the Great Wall, the Qingyang area and the Pingliang area in Gansu province are also included, they form a big circular image. The Shanctunbashan roke mass is located in shangxian area and the Bashan are between the Qinling mountain and the Yangtze River. The Yikezhaomeng roke mass is on the north of the Great Wall.
- It has very clear boundary between the northern edge and the southern edge in the Fengweihe Rift. Both edges can be joined with each other on the images, for example, the Fuping -Yanling - Sanyuan triangular area near the northern edge of the valley corresponds with the source area of the Chane River near the northern edge of the valley corresponds with the source area of the Chane River near the northern edge, and the Hancheng corresponds with the northern foot of the Zhongtiaoshan mountain and so on.
- The image feature between the Lishan land mass and the Shougtaoshan land mass corresponds with that near Qinling mountains, and they are same in lithogy particularly.
- There are two groups of X shear faults at the tangent parts among the shandei roke mass and the Bashan roke mass and the Yikezhaomeng roke mass. they are F3 and F4, F1 and F2
- The Feng -Weihe Rift isjust located between the Shanbei roke mass and the Shangyunbashan roke mass, and the graben is inclined towards the Shanbei roke mass and the Yikezhaomeng roke mass.
- The points of intersection at this two groups of the X shear faults are separately located at the narrow ends of Fenhe-weihe Rift and Dingbian Rift.
Appendix I
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