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Geology and Minerals

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The rock strata in Jinguashi mining area are mainly sedimentary rock strata, while some of them are igneous rock.


According to the history of geological evolution, about 10 to 8 million years ago, the Philipine Sea Plate at southeastern Taiwan and the Eurasian plate where Taiwan Island is located began to collide. In addition to forming many northeast-southwest oriented folds or thrust faults, about 1.7 million to 900,000 years ago, magmatic activities occurred, and formed a number of intrusive and eruptive igneous bodies, including the Keelung Mountain, Wudan Mountain, Ben Mountain(Benshan) , Cao Mountain, Jimu Mountain, Xin Mountain, Jiufen Andesite body, and so on. Immediately thereafter, many north-south oriented high-angle faults occurred, and the volcanic hydrothermal fluids upwelled along these north-south faults and many parallel minor faults and fracture zones in the vicinity, where "hydrothermal mineralization" occurs, resulting in the formation of major gold ore bodies in Jinguashi and Jiufen area. In addition, with the continuous tectonic movement, the land in this area has been uplifted, so that the deep underground ore bodies can be lifted up to the present elevation together with the surrounding rock bodies.


The overlying rock layer on the upper part of the ore body has also been removed by erosion during the one million years since the creation of the gold mine, leaving part of the gold ore body exposed on the surface, and many of the gold ores from the shallow ore body have even been washed down by the rain into the rivers. As a result, alluvial gold can be found in streams in the vicinity of Jinguashi and Jiufen, and even as far as the Keelung River in Badu area. This is also the beginning of the history of gold mining in Jinguashi.


In addition to gold, there are many other noteworthy minerals in the strata of Jinguashi region. Some of these minerals have economic value and can be mined and refined into useful substances, while others have become treasures for stone collectors because of their unique or beautiful appearance. And some other minerals, though unassuming in appearance, are important indicators of gold discoveries.


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