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3. PetrographyThe Wudehe plutons mainly consist of quartz diorite and granodioriteor corresponding porphyries whereas the Kuogeshaye dikes aremainly dioritic porphyrite. The intrusive rocks in the Wudehe No. 2pluton exhibit fine-medium and medium-coarse-grained inequigranularor porphyry texture and mainly contain plagioclase (30–40 vol.%),hornblende (15–20 vol.%), biotite (5–15 vol.%) and quartz (b5 vol.%).Accessory minerals include pyroxene, magnetite, titanite, zircon andapatite. Plagioclase, up to 3 mmin size, is themost abundant phenocrystphase in all of the Wudehe No. 2 intrusive rocks. They are generallyeuhedral and lath-shaped, and some of them show polysynthetictwinning. Hornblende occurs as euhedral phenocrysts with 300–600 μm in size, but some crystals are altered. Biotite phenocrysts,100–500 μmin size, are transparent brown and subhedral. The intrusiverocks contain minor quartz, which has a round shape caused byresorption. Pyroxene is rare in the intrusive rocks. Fe–Ti oxides appear asmicrophenocrysts andmicrolites in the matrix, or as inclusions in otherphases (e.g., hornblende).The porphyries in the Wudehe No. 5 pluton contain phenocrystsup to 2 mm. They contain plagioclase (30–45 vol.%), hornblende(15–20 vol.%), biotite (10–15 vol.%), pyroxene (3–6 vol.%), quartz(b5 vol.%), and minor titanite, rutile, apatite, magnetite, and zircon.Plagioclase phenocrysts are generally euhedral with polysynthetictwinning. Hornblende commonly occurs as transparent euhedralphenocrysts. Brown biotite occurs as euhedral phenocrysts. Somebiotite granules are altered to chlorites and epidote. Pyroxenephenocrysts are sometimes altered to hornblende along grainboundaries.The Kuogeshaye dioritic porphyrites consist of plagioclase (15–30 vol.%), hornblende (10–20 vol.%), biotite (5–15 vol.%), pyroxene (5–15 vol.%), and accessory minerals similar to those in the Wudeheintrusive rocks. Pyroxene phenocrysts in the Kuogeshaye dioriticporphyries are abundant relative to those of the