Postgraduate Profiles

Yongjun Lu

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Thesis: Tectonic Setting, Magmatic Evolution and Metallogenesis of Cenozoic Alkali Intrusions in the Eastern Indo-Asian Collision Zone, Yunnan, China

The 1,000-km-long, north- and northwest-striking, so called Jinshajiang-Ailaoshan alkali-rich magmatic belt spans along the eastern margin of the Tibetan plateau through China and into adjacent Vietnam and Laos. It is a significant porphyry Cu-Mo-Au province in China with over 10 million tons of copper metal and several hundred tons of gold metal. The porphyry deposits are spatially and temporally associated with the Cenozoic alkali intrusions. This project will focus on the middle segment of the magmatic belt between Dali and Lijiang area where the alkali intrusions are well exposed.

The main objectives of the proposed project are:

Characterize the lithology and geochemistry of the alkali intrusion, unraveling the origin and evolution of approximately nine significant alkali intrusions;

Distinguishing compositional or process differences between mineralized and barren intrusions;

Determine the age of the alkali intrusion, establishing the P-T uplift and erosion history of the intrusion;

Produce an ore deposit model to explain the styles and variations in mineralization related to the alkali intrusion

Why my research is important

This work attaches great importance to economic geology both disciplinarily and regionally.

Firstly, the Jinshajiang-Ailaoshan porphyry Cu-Mo-Au deposits and associated alkali intrusions were apparently developed in a post-collisional continental setting. As a result, the origin of magmas is not related to slab subduction which is traditionally recognized as the typical circum-Pacific setting for the formation of porphyry Cu-Mo-Au deposits. In addition to the different tectonic setting, these post-collisional continental porphyry deposits result from different magmatic sources and potentially different processes from those in traditional subduction-related arcs. However, this style of porphyry deposits is poorly known by the international scientific community. This work will directly address the magmatic origin and evolution of the alkali intrusions in order to better understand the formation of the porphyry Cu-Mo-Au deposits in this unusual setting.

Second, many previous age determinations on Cenozoic alkali intrusions used the K-Ar and Rb-Sr methods and are of variable quality or difficult to interpret. This project will systematically determine the age of the intrusions and related rocks in the region, utilizing SHRIMP and Ar-Ar dating technique. It will provide the scientific community with a large number of high-quality age data. In addition, the petrogenesis of the alkali intrusion in the region is highly controversial. Thus, this project will utilize the state-of-the-art LA-MC-ICPMS technique to determine the Lu-Hf isotopic composition of the zircons extracted from the intrusion. This method will further constrain the petrogenesis of the alkali intrusions and identify the source of the magmas.

Funding

Mar 2008

Mar 2011

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