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| 1 | Carboniferous adakites and Nb-enriched arc basaltic rocks association in the Alataw Mountains, north Xinjiang: interactions between slab melt and mantle peridotite and implications for crustal growth显示文摘Adakites and Nb-enriched arc basaltic rocks (NEABs) are identified to occur within the Carboniferous arc volcanic sequence in the Alataw Mountains, Xinjiang. The adakites, which consist of calc-alkaline dacites and rhyolites, are characterized by strong depletion of heavy rare earth elements (HREEs) (e.g., Yb) and Y, high Sr contents and Sr/Y ratios, either with no Eu anomalies or obvious positive Eu anomalies, apparent positive Sr anomalies, and depleted Nb and Ti. The Alataw adakites are very geochemically similar to the adakites that were presumably derived from partial melting of subducting oceanic crust. The rhyolitic adakite in the Alataw Mountains shows low MgO contents of 0.35% and Mg# values of about 17. However, the dacitic adakite shows high MgO contents of 2.67% to 3.32% and Mg# values of 53 to 58, suggesting that the adakite was possibly contaminated by mantle peridotite. On the other hand, the NEABs are characterized by Na-rich (Na2O/K2O > 2.0), high P2O5 and TiO2 contents, positive to weakly negative Nb anomalies, and non-negative Ti anomalies, suggesting that the NEABs were probably derived from partial melting of mantle peridotite that interacted with slab melt under high geothermal gradient. The Alataw adakites were probably derived from partial melting of oceanic crust on the southern margin of the Junggar plate that was subducted beneath the Bole block in the Carboniferous. The Alataw adakites-NE- ABs association implies that the partial melting of the subducting oceanic crust and the succedent interactions between the slab melt and peridotite in the mantle wedge possibly took place under the Bole arc in Carboniferous. On the southern margin of the Junggar plate, the Carboniferous subduction of oceanic crust (basin) was possibly extensive in the late Paleozoic era. In the Alataw area, high geothermal gradient possibly occurred in Carboniferous, and partial melting of subducting oceanic crust was a probable mechanism of Carboniferous regional crust growth. | WANGQiang ZHAOZhenhua BAIZhenghua BAOZhiwei XIONGXiaolin MEIHoujun XUJifeng WANGYixian | 2003 | Chinese Science Bulletin2003，48，19： | 44 |
| 2 | SHRIMP U-Pb zircon geochronology of Yangfang aegiriteaugite syenite in Wuyi Mountains of South China and its tectonic implications显示文摘In addition to the wide spread peraluminous granites, some alkaline or alkali-rich intrusive rocks were recently observed in the Wuyi Mountains. The Yangfang aegiriteaugite syenites in the Wuyi Mountains are strongly enriched in light rare earth elements (LREE), K, Ba, Ga, Zr and Y. What is more, differentiations of REE are obvious. In addition, the Yangfang aegiriteaugite syenites have also some characteristics similar to A-type granite. Zircons are selected from the Yangfang aegiriteaugite syenites for Sensitive High-Resolution Ion Microprobe (SHRIMP-Ⅱ) U-Pb geochronology study. 15 analyses give concordant 206Pb/238U ages in a narrow range of 233—249 Ma, which correspond to a single age population with a weighted mean 206Pb/238U age of 242 4 Ma, which records the crystallization time of the aegiriteaugite syenites. It is suggested that: (1) there were early Triassic peralkaline intrusive rocks in South China; (2) the early Indosinian extension event was probably active in local area, South China. This discovery provides a new insight for farther understanding of 揑ndosinian orogeny in South China. | WANGQiang ZHAOZhenhua JIANPing BAOZhiwei XlONGXiaolin MAJinlong | 2003 | Chinese Science Bulletin2003，48，20： | 20 |
| 3 | Organic Geochemistry of Sedimentary Rock-hosted Disseminated Gold Deposits in Southwestern Guizhou Province, China显示文摘Sedimentary rock-hosted disseminated gold (SRHDG) deposits in the Youjiang-Nanpanjiang Basin, southwestern Guizhou Province are commonly hosted by the same fold crests that commonly contain a remarkable amount of organic material. The total organic carbon (TOC) contents of the ores and host rocks are usually less than 1%. The reflectance of vitrinite and pyrobitumen in the ores and the host rocks ranges from 1.5% to 4.5%, often in the range of 2% to 3%. In the Lannigou deposit, the reflectance of vitrinite and pyrobitumen in the ores is usually somewhat higher than those within the host rocks, indicating a hydrothermal impact on the organic matter in the altered host rocks. On the contrary, the estimated maximum paleotemperatures of the Getang and Zimudang deposits are higher than the homogenization temperatures of the fluid inclusions in the ores, signifying that the organic matter maturation predated Au mineralization. No correlation between the organic matter contents and Au concentrations were recognized in the ores. However, the most striking observation is that there is a positive correlation between the S2 (a parameter of Rock-Eval analysis), Au and As contents of the ores in the Lannigou deposit. Organic matter maturation and migration is apparent from the TOC vs. HCI diagram. Furthermore, group analysis of the dichloromethane extractable organic component of the ores and host rocks shows that the maturation degree of the organic matter in the ores is slightly higher than that of the host rocks in the Lannigou gold deposit. However, the compositions of their alkanes, steranes and terpenes, which serve as biomarkers, are quite similar; this suggests that the organic matter found in the ores and host rocks has a common marine source. Organic matter probably contributed to the preconcentration of Au in the host rocks. Hydrocarbons in the system, on the other hand, clearly contributed to the emplacement of the gold mineralization through thermal sulfate reduction. Organic matter in the solution might have increased the potential of the hydrothermal solution to transport Au. | BAOZhiwei ZHAOZhenhua JayantaGUHA | 2005 | Acta Geologica Sinica(English Edition)2005，79，1： | 7 |
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