科研之友
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摘要
The Mesozoic intermediate-acid intrusive rocks in Tongling area can he divided into two magmatic series, namely the shoshonitic series and the high-potassium (K) calc-alkaline series. The shoshonitic series is characterized by an association of pyroxene monzodiorites (PMD) + monzonites (Mz) + quartz monzonites (QM), and high Rittmann indices. This series has common association with gold deposits. This series is associated cumulate enclaves such as pyroxene cumulate, hornblende cumulate and hornblende gabbro. The high-potassium calc-alkaline series is an association of gabbro-diorite (GBD) + quartz monzodiorites (QMD) + granodiorites (GD). It has lower Rittmann indices and REEs than the shoshonitic series and is associated with copper deposits. This series contains three kinds of enclaves, mica-enriched enclaves, which appear to be melted pelitic rock, mafic quartz monzodiorite enclaves and micro-diorite enclaves. The two series overlap in age. Zircon U-Pb SHRIMP ages for the quartz monzodioirite are around 140Ma, for the granodioirte are 142 similar to 146Ma, for the gabbro-diorite is 143Ma, for pyroxene monzodiorites are 138 similar to 142Ma and monzonite is 143Ma. From the differences in chemistry between the two suites study and the different kinds of enclaves found in each, we conclude that the shoshonitic series magma is derived from the differentiation of the mantle-derived alkaline basic magma and the high-potassium (K) calc-alkaline series magma is mixture between the differentiated mantle magma and crustal magma.
- 出版日期2010-9
- 单位中国地质科学院
