Xiaoxinancha Cu-(Au) deposit, Hunchun Co., Yanbian Chaoxianzu Autonomous Prefecture, Jilin Province (Manchuria; Dongbei Region), China

Large-scale porphyry Cu-(Au) deposit, located in the intersection of the Tianshan-Jilin (Heilongjiang) EW-trending Paleozioc accretion zone and the Circum Pacific Mesozoic tectono-magmatic zone. The oldest exposed strata are early Paleozoic rocks of the Qinglong Group, that often occur as xenoliths in late Hercynian granite and diorite and consist of amphibolite, amphibolitic gneiss, biotite schist, graphite schist, andalusite slate, sillimanite slate and sandy slate. Dispersed early and Late Permian strata, distributed in the adjacent region, are composed of intermediate-siliceous tuff, volcanic brecciae, lava and sandy slate. Jurassic volcanic rocks can be seen in the fault basins south and northwest of the deposit. Ingneous intrusives account for more than 60% of the deposit area, including Hercynian, Indosinian, Yanshannian and Himalayan igneous bodies. Hercynian intrusives are dominant; they consist of plagioclase granite, biotite-plagioclase granite, gneissoid biotite granite and diorite. The main host rock is Hercynian diorite. During early Yanshannian stage, many kinds of intrusives formed, including diorite, quartz diorite, granite, diorite porphyry, moyite, adamellite and granitic porphyry. They occur as small igneous stocks or dikes of Hercynian granite and Jurassic volcanic rock. Intermediate porphyries, especially diorite porphyry (130.1 Ma), are closely related with Cu and Au minerals. The deposit is controlled by the intersection of NW-and NNE-striking faults. There are 34 orebodies in a NNW-trending belt with an area of 2.4-1.8 km2. The bodies are composite vein type, single vein type, network type, as well as veinlets and disseminations. Wallrock alterations include K-feldspar alteration, biotitization, beresite alteration, propylitic alteration and carbonate alteration.

The deposit consists of two sections that are separated by a fault: the northern section is composed of altered rocks with veinlet-dissemination sulfides and melnicovite-dominated sulfide-quartz veins, and is explored by the Beishan Mine; the southern section, worked by the Nanshan Mine, consists of pyrrhotite-dominated sulfide-quartz veins and pure sulfide veins.

References:
- Chil-Sup So, Bai-Lu Jin, Seong-Taek Yun, Chul-Ho Heo, and Seung-Jun Youm (2002): Alteration and mineralization in the Xiaoxinancha porphyry copper deposit, Yianbin, China: Fluid inclusion and sulfur isotope study. Economic and Environmental Geology 35(3), 211-220.
- Bin Liu (2003): Preliminary Study on the Minerogenetic Model of Mesozoic Volcanic-Magmatic Rocks in Eastern Jilin, China. Geology and Resources [Dizhi Yu Ziyuan] 12(2), 72-77.
- Hong-Guang Zhao, Jing-Gui Sun, Jun-Qing Chen, Jun-Kang Zhao, Feng-Liang Yao, and Zhan Duan (2005): The Genesis and Evolution of Ore-bearing Fluids of the Xiaoxinancha Gold-bearing Porphyry Copper Deposit in Yanbian Area: H, O, C, S, Pb Isotope Tracing. Journal of Jilin University (Earth Science Edition) [Jilin Daxue Xuebao (Diqiu Kexue Ban)] 35(5), 601-606.
- Sun Jinggui, Zhao Junkang, Chen Junqiang, Keisuke Nagao, Hirochika Sumino, Shen Kun, Men Lanjing, and Chen Lei (2008): Ore-forming mechanism for the Xiaoxinancha Au-rich Cu deposit in Yanbian, Jilin Province, China: Evidence from noble gas isotope geochemistry of fluid inclusions in minerals. Science in China, Series D (Earth Sciences), 51(2), 216-228.