The Zudong and Guanxi granites are original rocks of the ion adsorption-type HREE and LREE deposits in weathering crust of granites. The ΣREE value and LREE/HREE ratio of the Zudong granite are 264 ppm and 0.81-0.24 ...The Zudong and Guanxi granites are original rocks of the ion adsorption-type HREE and LREE deposits in weathering crust of granites. The ΣREE value and LREE/HREE ratio of the Zudong granite are 264 ppm and 0.81-0.24 respectively, and the average Y/ΣREE ratio is 35.8-54.5%. This is mainly due to magmatic crystallization and evolution and deuteric metasomatism (albitization, muscovitization and fluorite-doveritization). These alterations resulted in endogenic mineralizations of yttrium-group REE fluorine carbonates, silicates and arsenates. The Guanxi granite is characterized by LREE enrichment (the average LREE/HREE ratio is 2.43).展开更多
Objective Galuskin et al. （2011） firstly discovered that vorlanite （CaU^6＋/4＋）04 is a rare Ca-rich mineral with a fluorite-type structure, which is isostructural with uraninite （U^4＋O2）. Previous studies of ...Objective Galuskin et al. （2011） firstly discovered that vorlanite （CaU^6＋/4＋）04 is a rare Ca-rich mineral with a fluorite-type structure, which is isostructural with uraninite （U^4＋O2）. Previous studies of the Xianshi granite-related uranium deposit reported that uraninite and pyrite are the major ore minerals whereas galena, clausthalite （PbSe）, and pyrite are minor phases in the ores. A more detailed petrographic and geochronological study of the uranium minerals from the Xianshi deposit showed that there are three distinct types of uraninite-bearing assemblages which formed at three mineralization episodes （Fig. la; Luo et al., 2015）.展开更多
Carbonatites are commonly related to the accumulation of economically valuable substances such as REE, Cu, and P. The debate over the origin of carbonatites and their relationship to associated silicate rocks has been...Carbonatites are commonly related to the accumulation of economically valuable substances such as REE, Cu, and P. The debate over the origin of carbonatites and their relationship to associated silicate rocks has been ongoing for about 45 years, Worldwide, the rocks characteristically display more geochemical enrichments in Ba, Sr and REE than sedimentary carbonate rocks. However, carbonatite＇s geochemical features are disputed because of secondary mineral effects. Rock-forming carbonates from carbonatites at Qinling, Panxi region, and Bayan Obo in China show REE distribution patterns ranging from LREE enrichment to flat patterns. They are characterized by a Sr content more than 10 times higher than that of secondary carbonates. The coarse- and fine-grained dolomites from Bayan Obo H8 dolomite marbles also show similar high Sr abundance, indicating that they are of igneous origin. Some carbonates in Chinese carbonatites show REE （especially HREE） contents and distribution patterns similar to those of the whole rocks. These intrusive carbonatites display lower platinum group elements and stronger fractionation between Pt and lr relative to high-Si extrusive carbonatite. This indicates that most intrusive carbonatites may be carbonate cumulates. Maoniuping and Daluxiang in Panxi region are large REE deposits. Hydrothermal fluorite ore veins occur outside of the carbonatite bodies and are emplaced in wallrock syenite. The fluorite in Maoniuping has Sr and Nd isotopes similar to carbonatite. The Daluxiang fluorite shows Sr and REE compositions different from those in Maoniuping. The difference is reflected by both the carbonatites and rock-forming carbonates, indicating that REE mineralization is related to carbonatites. The cumulate processes of carbonate minerals make fractionated fluids rich in volatiles and LREE as a result of low partition coefficients for REE between carbonate and carbonatite melt and an increase from LREE to HREE. The carbonatite-derived fluid has interacted with wallrock to form REE ore veins. The amount of carbonatite dykes occurring near the Bayan Obo orebodies may support the same mineralization model, i.e. that fluids evolved from the carbonatite dykes reacted with H8 dolomite marble, and thus the different REE and isotope compositions of coarse- and fine-grained dolomite may be related to reaction processes.展开更多
Luku alkali syenite is distributed throughout the southern end of the Hongge basic-ultrabasic intrusion in Panzhihua,Sichuan,SW China.Using LA-ICP-MS,the alkali syenite intrusion yielded a zircon U-Pb age of_(2)64.5&#...Luku alkali syenite is distributed throughout the southern end of the Hongge basic-ultrabasic intrusion in Panzhihua,Sichuan,SW China.Using LA-ICP-MS,the alkali syenite intrusion yielded a zircon U-Pb age of_(2)64.5±1.6 Ma,concordant with the ages of the E’meishan large igneous province(260 Ma).The intrusion displayed silica-saturated,Al-adequate and alkali-rich signatures,with SiO_(2)62.07%-64.04%,Al_(2)O_(3)16.26%-16.79%and Na_(2)O+K_(2)O 9.17%-9.91%(averaging 9.31%).The rock falls into the alkaline zone on the SiO_(2)-A.R.diagram,as well as in the potassium zone on the K_(2)O-Na_(2)O diagram,indicating a potassium alkaline rock.The rock has a low total REE concentration and showed enrichment in LREE(LREE/HREE=7.06-7.95),typical negative Eu anomalies(δEu=0.73-0.80),trace element deficiencies in LILEs(Ba,K,Sr,Zr)and enrichment in HFSEs(Th,U,Nd,Sm,Ta and Nb),displaying crust and mantle element information.Zircons show a strong positive Ce anomaly and negative Eu anomaly,similar to the characteristics of crustal source magmatic zircon,however the(Lu/Gd)N ratio ranges from 1.48 to 3.17,and the(Yb/Sm)N ratio ranges from 38.49 to 77.15,which are similar to the characteristics of mantle-derived magmatic zircon.In the La/Yb-δEu correlation diagram,the data plots near the boundary between crust type and crust-mantle type.From the combined‘trinity’spatiotemporal relationship of Indosinian intermediate-acid alkali intrusive rocks in the Panxi area with E’meishan basalt and basic-ultrabasic intrusive rocks,the regional tectonic evolution and the partial melting model of the most intraplate magma sources,we believe that the Luku alkali syenite in Sichuan was formed from the partial melting of a crust-mantle source material,due to underplating of the mantle plume basic magma.展开更多
文摘The Zudong and Guanxi granites are original rocks of the ion adsorption-type HREE and LREE deposits in weathering crust of granites. The ΣREE value and LREE/HREE ratio of the Zudong granite are 264 ppm and 0.81-0.24 respectively, and the average Y/ΣREE ratio is 35.8-54.5%. This is mainly due to magmatic crystallization and evolution and deuteric metasomatism (albitization, muscovitization and fluorite-doveritization). These alterations resulted in endogenic mineralizations of yttrium-group REE fluorine carbonates, silicates and arsenates. The Guanxi granite is characterized by LREE enrichment (the average LREE/HREE ratio is 2.43).
基金supported by the National Key R&D Program of China (grant No. 2016YFC0600405)the Strategic Priority Research Program (B) of CAS (grant No. XDB18030202)+2 种基金the Natural Science Foundation of China (41603051)the Key Program of Science and Technology of Guizhou (grant No. [2018]1423)CSC program to Luo
文摘Objective Galuskin et al. （2011） firstly discovered that vorlanite （CaU^6＋/4＋）04 is a rare Ca-rich mineral with a fluorite-type structure, which is isostructural with uraninite （U^4＋O2）. Previous studies of the Xianshi granite-related uranium deposit reported that uraninite and pyrite are the major ore minerals whereas galena, clausthalite （PbSe）, and pyrite are minor phases in the ores. A more detailed petrographic and geochronological study of the uranium minerals from the Xianshi deposit showed that there are three distinct types of uraninite-bearing assemblages which formed at three mineralization episodes （Fig. la; Luo et al., 2015）.
基金financially supported by the Chinese National Science Foundation(Nos. 40973040,40773021)the West Light Foundation of Chinese Academy of Sciences and the Young Talent Plan of Peking University to Xu
文摘Carbonatites are commonly related to the accumulation of economically valuable substances such as REE, Cu, and P. The debate over the origin of carbonatites and their relationship to associated silicate rocks has been ongoing for about 45 years, Worldwide, the rocks characteristically display more geochemical enrichments in Ba, Sr and REE than sedimentary carbonate rocks. However, carbonatite＇s geochemical features are disputed because of secondary mineral effects. Rock-forming carbonates from carbonatites at Qinling, Panxi region, and Bayan Obo in China show REE distribution patterns ranging from LREE enrichment to flat patterns. They are characterized by a Sr content more than 10 times higher than that of secondary carbonates. The coarse- and fine-grained dolomites from Bayan Obo H8 dolomite marbles also show similar high Sr abundance, indicating that they are of igneous origin. Some carbonates in Chinese carbonatites show REE （especially HREE） contents and distribution patterns similar to those of the whole rocks. These intrusive carbonatites display lower platinum group elements and stronger fractionation between Pt and lr relative to high-Si extrusive carbonatite. This indicates that most intrusive carbonatites may be carbonate cumulates. Maoniuping and Daluxiang in Panxi region are large REE deposits. Hydrothermal fluorite ore veins occur outside of the carbonatite bodies and are emplaced in wallrock syenite. The fluorite in Maoniuping has Sr and Nd isotopes similar to carbonatite. The Daluxiang fluorite shows Sr and REE compositions different from those in Maoniuping. The difference is reflected by both the carbonatites and rock-forming carbonates, indicating that REE mineralization is related to carbonatites. The cumulate processes of carbonate minerals make fractionated fluids rich in volatiles and LREE as a result of low partition coefficients for REE between carbonate and carbonatite melt and an increase from LREE to HREE. The carbonatite-derived fluid has interacted with wallrock to form REE ore veins. The amount of carbonatite dykes occurring near the Bayan Obo orebodies may support the same mineralization model, i.e. that fluids evolved from the carbonatite dykes reacted with H8 dolomite marble, and thus the different REE and isotope compositions of coarse- and fine-grained dolomite may be related to reaction processes.
基金This work was supported by the China Geological Survey(Grant Nos.DD20189501 and DD20190446).
文摘Luku alkali syenite is distributed throughout the southern end of the Hongge basic-ultrabasic intrusion in Panzhihua,Sichuan,SW China.Using LA-ICP-MS,the alkali syenite intrusion yielded a zircon U-Pb age of_(2)64.5±1.6 Ma,concordant with the ages of the E’meishan large igneous province(260 Ma).The intrusion displayed silica-saturated,Al-adequate and alkali-rich signatures,with SiO_(2)62.07%-64.04%,Al_(2)O_(3)16.26%-16.79%and Na_(2)O+K_(2)O 9.17%-9.91%(averaging 9.31%).The rock falls into the alkaline zone on the SiO_(2)-A.R.diagram,as well as in the potassium zone on the K_(2)O-Na_(2)O diagram,indicating a potassium alkaline rock.The rock has a low total REE concentration and showed enrichment in LREE(LREE/HREE=7.06-7.95),typical negative Eu anomalies(δEu=0.73-0.80),trace element deficiencies in LILEs(Ba,K,Sr,Zr)and enrichment in HFSEs(Th,U,Nd,Sm,Ta and Nb),displaying crust and mantle element information.Zircons show a strong positive Ce anomaly and negative Eu anomaly,similar to the characteristics of crustal source magmatic zircon,however the(Lu/Gd)N ratio ranges from 1.48 to 3.17,and the(Yb/Sm)N ratio ranges from 38.49 to 77.15,which are similar to the characteristics of mantle-derived magmatic zircon.In the La/Yb-δEu correlation diagram,the data plots near the boundary between crust type and crust-mantle type.From the combined‘trinity’spatiotemporal relationship of Indosinian intermediate-acid alkali intrusive rocks in the Panxi area with E’meishan basalt and basic-ultrabasic intrusive rocks,the regional tectonic evolution and the partial melting model of the most intraplate magma sources,we believe that the Luku alkali syenite in Sichuan was formed from the partial melting of a crust-mantle source material,due to underplating of the mantle plume basic magma.
