The Yunnan Himalayan alkaline rich porphyry occurs as a compound rockbelt and consists of calca alkalic, alkaline and peralkaline intrusions. Its origin is in debate. The paper deals with its origin by studying rock′...The Yunnan Himalayan alkaline rich porphyry occurs as a compound rockbelt and consists of calca alkalic, alkaline and peralkaline intrusions. Its origin is in debate. The paper deals with its origin by studying rock′s REE and Sr isotope. Although the rocks are different in their REE contents varying from 77.53 μg/g to 1 798.3 μg/g, they have very similar features in REE parameters. On the triangalar diagram of REEs, the sample dots are concentrated on the end area of light REEs, representing a product of low degree melting of upper mantle or lower crust materials. The initial 87 Sr/ 86 Sr values of rocks vary between 0.706 4 and 0.709 8, showing a feature of mantle crust mixed source. Moreover, REEs show a logarithmic linear positive correlation between them. This type of correlation strongly supports the fractional partial melting model. The result of geochemistry inversion shows that the source rock of alkaline rich porphyry is plagioclase bearing harzburgite and of mantle crust mixed type. At the early state of melting, some crust components of the source rock were partially melted into intermediate acidic magma; with the crust components consumed, the magma evolved to basic.展开更多
The age of alkali rich porphyries in the western margin of Yangtze Platform is 30—50 Ma; the minerals mainly are orthoclase, quartz, plagioclase; the chemical composition is alkali rich [(K 2O+Na 2O)>8%],high ...The age of alkali rich porphyries in the western margin of Yangtze Platform is 30—50 Ma; the minerals mainly are orthoclase, quartz, plagioclase; the chemical composition is alkali rich [(K 2O+Na 2O)>8%],high potash[(K 2O+Na 2O)=5.09%-8.30%]; the content of REE is relatively low, LREE is concentrated, without anomaly of europium; the average initial ratio of 87 Sr/ 86 Sr is 0.7073; the value of δ 34 S similar to that of the meteoritic sulfur; the ratio of Pb isotope corresponds to that of upper mantle; metallogenic types belong to Cu, Mo, Au, Ag, Pb, Zn polymetal mineralization and rare, rare earth metal mineralization.展开更多
文摘The Yunnan Himalayan alkaline rich porphyry occurs as a compound rockbelt and consists of calca alkalic, alkaline and peralkaline intrusions. Its origin is in debate. The paper deals with its origin by studying rock′s REE and Sr isotope. Although the rocks are different in their REE contents varying from 77.53 μg/g to 1 798.3 μg/g, they have very similar features in REE parameters. On the triangalar diagram of REEs, the sample dots are concentrated on the end area of light REEs, representing a product of low degree melting of upper mantle or lower crust materials. The initial 87 Sr/ 86 Sr values of rocks vary between 0.706 4 and 0.709 8, showing a feature of mantle crust mixed source. Moreover, REEs show a logarithmic linear positive correlation between them. This type of correlation strongly supports the fractional partial melting model. The result of geochemistry inversion shows that the source rock of alkaline rich porphyry is plagioclase bearing harzburgite and of mantle crust mixed type. At the early state of melting, some crust components of the source rock were partially melted into intermediate acidic magma; with the crust components consumed, the magma evolved to basic.
文摘The age of alkali rich porphyries in the western margin of Yangtze Platform is 30—50 Ma; the minerals mainly are orthoclase, quartz, plagioclase; the chemical composition is alkali rich [(K 2O+Na 2O)>8%],high potash[(K 2O+Na 2O)=5.09%-8.30%]; the content of REE is relatively low, LREE is concentrated, without anomaly of europium; the average initial ratio of 87 Sr/ 86 Sr is 0.7073; the value of δ 34 S similar to that of the meteoritic sulfur; the ratio of Pb isotope corresponds to that of upper mantle; metallogenic types belong to Cu, Mo, Au, Ag, Pb, Zn polymetal mineralization and rare, rare earth metal mineralization.
