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一、温泉出露地区的地质、地貌条件 腾冲地处祖国的西南边疆(北纬25°06′,东经98°31′),是我国西南第四纪火山分布区。与火山活动相伴同,地震频繁,温泉出露亦多。该地的火山、地震和温泉,成为滇西南最突出的自然现象(附图1)。 在大地构造上,腾冲处于横断山块断带的西侧,西邻喜马拉雅褶皱带,位于两个不同构造单位的交接处,地壳极不稳定,岩浆活动频繁。中生代末期的燕山运动使本区地层产生南北向的巨型褶皱隆起与大规模的花岗岩体的侵入,并形成一系列与褶皱同向的走向大断层。在早第三纪又受到喜马拉雅运动的影响,形成了数组北东、北西、东西向的断层,成为滇西的主要断裂破碎带之一。后来的各期火山活动以及地震和温泉等都是沿着上述地壳脆弱的破碎地带发生的。
I. Geological and geomorphological conditions of the hot spring exposed areas Tengchong is located in the southwestern frontier of the motherland (latitude 25o 06 ’, longitude 98o 31’) and is the Quaternary volcanic distribution area in southwestern China. Accompanied by volcanic activity, earthquakes are frequent and hot springs are exposed. Volcanoes, earthquakes and hot springs in the area have become the most prominent natural phenomenon in southwestern Yunnan (Figure 1). On the tectonic setting, Tengchong is located on the west side of the Hengduanshan fault belt, west of the Himalayan fold belt, at the junction of two different tectonic units. The crust is extremely unstable and magmatic activity is frequent. The Yanshan movement in the late Mesozoic resulted in the north-south trending giant fold uplift and large-scale granite intrusions in this area, and a series of fault-trending strike-to-slip faults were formed. In the early Tertiary period, it was affected by the Himalayan movement and formed an array of north-east, north-west and east-west faults, becoming one of the major fault broken zones in western Yunnan. Later periods of volcanic activity as well as earthquakes and hot springs all took place along the crustal crust above the crust.