Alkaline Intrusives of Lutingshan and Ch'iaoshan in S. Shansi *

The known areas of alkaline rocks in Shansi are all situated in or near regions where different systems of trendlines meet. As indicated on any map of Shansi by the sudden diversion of the Fenho river towards W we should find near the bend a crossing of trendlines and it is here that the Linfen (P'ingyang) intrusives are situated. The newly discovered intrusives, which are described in this paper, are Lutingshan and Ch'iaoshan and they may be considered distant satellies of the main intrusive body Lungwangmiao (cfr. Nyström: Some alkaline rocks of Shansi province). They are both typical “shoulder” intrusives, reinforcing the edge of a limestone plateau. Lutingshan of which the highest eminence consists of Carboniferous sandstone, harbours in its S slope an almost circular stock of about 4000 m. diameter, the most striking feature of which is its topography. The rock composing this igneous body is obviously of two different kinds: the rim showing a jagged “shark's teeth” contour has offered stronger resistance to erosion, wheras the centre is deeply excavated, the whole resulting in what one may call a “pseudo‐crater”, about 200 m. deep. The rim rock is light grey banatite, inclining to akerite, and the centre a red, easily weathered alteration‐product of banatitic orgin, the alteration probably being of hydrothermal nature and having taken place during the latter stages of solidification. There are veins of pink gramte‐aplitic composition in the rim. There are highly metamorphosed inliers of limestone in die southern part of the intrusive and here a valley provides an outlet from the “crater”. There is also a narrow canyon providing exit towards SW. These topographical features are without parallel in the other alkaline areas in Shansi. The other intrusive Ch'iaoshan may be seen from Lutingshan at a distance of a few km. towards E. It looks like a dark, cone‐like eminence, rising above the rather undisturbed layers of Ordovician limestone. At closer inspection it is seen that this cone represents the northern semicircular part of a bat‐tike intrusive which spreads along a faultline running NE‐SW. It is sculptured in numerous peak, of which the northern eminence, mentioned above, is the highest. The topography suggests a variety of rocks of different hardness. Ch'iaoshan no doubt marks the spot where, through intersection of trendlines, the crust has been particularly weakened. This is also made probable by the numerous satellites which—in contrast to Lutingshan—are very prevalent round Ch'iaoshan. The high northern peak consists of a coarse crumbling pink porphyrv extremely affected by cleavage. Towards the centre of die intrusive the rock becomes more dense and firm but there are numerous miarolithic cavities. It is of light pink colour and has bisilicate crystals scattered throughout. Since this seems to be fairly representative of a large mass of the intrusive, a chemical analysis was made and the composition is strongly alkaline, but with quartz, in fact a nordmarkite and very similar to certain alkaline rocks of W Shansi. There are dykes, of a snow‐white banatite and veins of granite‐aplite, showing thus rapid differentiation both in a dioritic and in a granitic direction. The satellites are of banatitic character. Here and there grass‐green patches of epidote are seen in die outlying parts of the intrusive. No inliers of limestone have been seen. Concerning the association of rocks in these two intrusives, they show undoubted consanguineity both with each other and with the parent intrusive Lungwangmiao. From a hypothetical parent rock of akeritic composition there has been differentiation both in a granitic (aplitic) and in a dioritic (banatitic) direction. The syenitic differentiation (resulting ultimately in nepheline and nosean‐bearing rocks) so characteristic for die alkaline areas in W. Shansi, is conspicuous by its absence and there are no alkaline pyroxens (aegirine or aeg. augite) to be seen. The nordmarkite in Ch'iaoshan is an intermediary member in the granitic differentiation process. Regarding the age of the intrusions it is not possible to arrive at anv definite conclusion because of the absence of sediments, contemporaneous, or younger than die igneous action. But since the intrusions are so obviously connected with the Fenho‐Weiho graben diastrophism, which produced fault‐scarps, along which Pliocene beds are interbedded with conglomerates from the scarps and since, on exposed surfaces of the parent (Lungwangmiao) intrusive, Hipparion‐beds can be found covering outcrops of igneous rocks, it seems that until further information is forthcoming, we may in a preliminary and tentative way establish the time of intrusion to be during the closing stages of maximum diastrophism of mid‐Tertiary time.