Handaqi Fm
Type Locality and Naming
The type section was not given, so the auriferous (gold-bearing) ore section west of Xiaogouhe River measured in “Handaqi Geological Map” is suggested as the representative section of this formation.
It was named by Zhao Guisan et al. in 1957.
Lithology and Thickness
Volcanics. It is composed of intermediate-basic to intermediate-acidic rocks and can be divided into several obvious eruption cycles. The Lower part of this Formation includes four cycles and is dominated by spilite, andesitic porphyrite, tuff and tuffaceous breccia, intercalated with intermediate-acidic tuff, tuffaceous sandstone and crystalline limestone lenses, totaling 752.5 m in thickness.
The Upper part, 400 to 500 m thick, is composed of intermediate-acidic and acidic lava, tuff, tuffaceous breccia and spilite interbeds.
Relationships and Distribution
Lower contact
It is in fault contact with the underlying Niqiuhe Fm.
Upper contact
It is conformably overlain by the Jinshui Fm.
Regional extent
This formation shows a northeastern band of distribution mainly in Handaqi area, and gets thinner along the strike or even thins out. Stretching northeastwards, only the upper part of the Handaqi Fm is developed in Wudaogou, and gradually changes into tuffaceous slate intercalated with intermediate-acidic volcanic rock. At 165 km of Namo Road, the Handaqi Fm, here only 20 m thick, is composed of purple dacitic porphyrite. From Sankuang northwards to the south bank of Chengduhe River, it is similar in lithology and the outcropped thickness is more than 84 m. In the middle reaches of Niqiuhe River the thickness is 529 m.
South of Handaqi and east of Huolongmen, the Handaqi Fm is also distributed where the thickness is more than 540 m and is dominated by intermediate-acidic lava and brecciform tuff.
GeoJSON
Fossils
In the interbeds of sedimentary origin, it yields brachiopods Discomyorthis sp., “Atrypa” sp. and coral Syringaxom sp., Lindstromia sp.
Age
Depositional setting
Additional Information