The Tongehang porphyry Cu( Mo-Au) deposit is located in southern segment of the Jinshajiang-Red River alkali-rich intrusive belt. The Tongchang quartz syenite porphyry intrusion is one important member of the Jinshajiang-Red River alkali-rich intrusions. Detailed geochemical study on the Tongchang quartz syenite porphyries indicates that it is characterized by high alkali, metaluminous to weakly peraluminous and enrichment in potassium, and belongs to shoshonitic rock. These rocks are obviously enriched in LILEs (such as Rb, Ba, Th, U, K, La and Sr, etc.), and depleted in HFSEs ( such as Ta, Nb and Ti, etc.), with "TNT" negative anomaly. They also have high Sigma REE and LREE contents and strong fractionation between LREEs and HREEs. The Sr-Nd isotopic compositions of the Tongchang quartz syenite porphyries exhibit a range of ((87)Sr/(86)Sr); ratios from 0. 707097 to 0. 707138, and epsilon(Nd) (t) values from -7. 1 to -6. 8. In the ((87)Sr/(86)Sr)(i)-epsilon(Nd) (t) diagram, the Tongchang quartz syenite porphyries are similar to those originated from EMII source. Compared with geochemical characteristics of the Yulong and Machangqing porphyries in northern and central segments of the Jinshajiang-Red River alkali-rich intrusive belt, respectively, the Tongchang porphyries are characterized by higher whole-rock alkali contents, higher ((87)Sr/(86)Sr), ratios, lower cm (t) values, and exhibit no adakitic affinitiy. An integrated study reveals that the Tongchang quartz syenite porphyries genetically belong to A-type granitoid, and formed in late collisional strike-slip setting at similar to 35Ma which were directly derived from partial melting of EMIL The geochemical characteristics of host porphyries and ore-forming scales of the Tongchang, Yulong and Machangqing porphyry Cu( Mo-Au) deposits have some notable diversities, which may have close relationship with the partial melting degrees and crustal contaminating degrees for their host porphyry sources.

Publication name	ACTA PETROLOGICA SINICA　Volume:27 　Issue:10 　Pages:3109-3122 　Published:OCT 2011
Author(s)	Xu LeiLuo; Bi XianWu; Su WenChao; Qi YouQiang; Li Liang; Chen YouWei; Dong ShaoHua; Tang YongYong
Corresponding author	XU LeiLuo  leiluoxu@sina.com,bixianwu@vip.gyig.ac.cn  Chinese Acad Sci, State Key Lab Ore Deposit Geochem, Inst Geochem, Guiyang 550002, Peoples R China

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