Research on the ultramafic rocks in the Laiyuan Batholith, Hebei Province

Chang, Zhaoshan, Feng, Zhongyan, and Chen, Tingli (2000) Research on the ultramafic rocks in the Laiyuan Batholith, Hebei Province. Geology and Prospecting, 36 (3). pp. 36-39.

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The Laiyuan batholith is in the Zijingguan deep fault belt and is composed of 3 series of intrusive rocks. this paper chooses the Yaogou hornblendite body, one of the two major ultramafic outcrops in the Laiyuan batholith, as a representative to carry out detailed research. Through the hornblendite outcrops are very small and is cut by later magma, they are concentrated ina small area. Immediately adjacent to the hornblendite is the pyroxene monzodiorite. Further away is the biotite quartz diorite which is fully gradational to the monzodiorite. There are hornblendite inclusions in the monzodiorite and the quartz diorite, mostly near the hornblendite body. The further from teh hornblendite body the smaller and less the bornblendite inclusions. The hornblendite features poikilitic texture. It consists maily of amphibole (53%), olivine (13%), bronzite (18%) and biotite (10%). The amphiboles include brown ones and green ones, both magnesiohastingite with no sharp boundaries between them. But the brown ones contain more Ti and Al(IV), which indicates their deep origin. The chrysolites are generally included in amphiboles and orthopyroxenes. There are small sulfide balls composed of chalcopyrite, cubanite and triolite in brown amphiboles. Mineralogical and textureal characteristics of teh 3 kinds of rocks indicate that the monzodiorite and the quartz diorite derived from the same magma. At the contact there are more early precipitated amphiboles and the monzodiorite undergone more strongly late magmatic alteration, such as K-feldsparization, sericitization, etc. The hornblendite was emplaced earlier than the quartz diorite. The major and trace element characteristics of teh hornblendite and the quartz diorite rocks differ greatly. The REE pattern indicate that teh hornblendite came from the mantle. The ampphibole K-Ar age of the hornblendite is 223 Ma and the quartz diorite 187 Ma.

The above facts indicate that the Yaogou bornblendite crystalize from an earlier, independent magma which came from the mantle. The magma ascended along the deep fault and formed the series rocks. Later at the same spot but shallower depth, magma generated and also emplaced along the deep fault at the beginning. Quartz diorite crystalized first. When more magma was emplaced they occupied the whole deep fault belt. Although the major part of teh Laiyuan batholith crystalised in the Late Jurassic-Early Cetaceous Epoth, the earliest part began to form as early as in the Late Triassic Epoch. Totally the magmatism lasted over 120 million years.

Item ID: 35300
Item Type: Article (Research - C1)
ISSN: 0495-5331
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Article in Chinese with English summary.

Date Deposited: 08 Sep 2014 00:10
FoR Codes: 04 EARTH SCIENCES > 0403 Geology > 040304 Igneous and Metamorphic Petrology @ 100%
SEO Codes: 84 MINERAL RESOURCES (excl. Energy Resources) > 8401 Mineral Exploration > 840102 Copper Ore Exploration @ 50%
84 MINERAL RESOURCES (excl. Energy Resources) > 8401 Mineral Exploration > 840105 Precious (Noble) Metal Ore Exploration @ 50%
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