Chapter XVII: Part 5: The Geology of the Ch’ing Ho and Hsi-Wan-Tzŭ District, Northern Chihli

Leaving Kalgan we travelled northward up the valley of the P’an-chang Ho for about six miles. The sides of this valley are steep and composed entirely of outcrops of trachyte of a mauve grey colour. This colour on the exposed surface is changed, through weathering, to a dark brown. Typical crystals of felspar occur throughout the mass. In the specimens gathered the crystals had undergone considerable decomposition.

At a place called Hsi-tien-tzŭ the valley takes a bend eastward, at right angles to its original course, while a wide but waterless valley enters it from the north. This is called Ching-kou, while the main valley, which has a good permanent stream, is now called Ch’ing Ho.

The trachyte continues all the way to Kao-chia-yin-tzŭ, just beyond which place it ends. Here it is of a lighter colour, the weathered surface being of a bright brick red, while the new fracture shows the rock itself to be of a light mauve-grey. The white crystals of felspar are also much larger and more noticeable than in the outcrops nearer Kalgan. Where they are exposed at the surface, these crystals rapidly disintegrate and are washed away, leaving the surface rock full of holes, which gives it something the appearance of a rock charged with air-bubbles.

Beyond Kao-chia-yin-tzŭ, still working eastward, we found metamorphic (chiefly gneiss) rocks, alternating with plutonic (granite), the former predominating.

Both the metamorphic and plutonic rocks are seamed with stringers, leads and ledges of quartz (probably auriferous).

At Hsin-yin-tzŭ the valley bends northward again, and subsequently continues winding in a general north-easterly direction to its source. From this village the outcrops are entirely of granite, felsite and serpentine, no metamorphic rocks occurring, till, just before Hsi-wan-tzŭ is reached, an extensive outcrop of gneiss is encountered.

Beyond Hsi-wan-tzŭ (i.e. to the east) we found the mountains to be composed entirely of a dark grey-brown or purple-grey trachyte containing the characteristic white crystals of felspar.