Based on the detailed geological investigation and record of galleries and drill holes, a new idea has beenadvanced that granodiorite is earlier than quartz monzodiorite porphyry. Both of them are products of two diff...Based on the detailed geological investigation and record of galleries and drill holes, a new idea has beenadvanced that granodiorite is earlier than quartz monzodiorite porphyry. Both of them are products of two differentmagmatic intrusive activities. The analysis results of trace elements show that the Sr content is beyond any othercrustal rock and the Th content is beyond that of Ta. The whole-rock analysis indicates that rockbody is rich in CaOand poor in K2O. In the composition of Pb istope of rockbody, the ratio of 207Pb to 204Pb is less than 15.60. Allthese show that the magma mainly comes from the upper mantle. Ti,Zr,Cr,Nb trace elements and the relation be-tween the Gardini index(τ) and the Rittmann index(σ) indicate that the rockbodies are formed in the orogenic beltand island arc tectonic setting. The summation (∑REE) and the characteristic value (m (La)/m (Yb)) of the rareearth elements show that the original rock is alkalic basalt. The analysis of the characteristic values of REE and thequantitative modeling calculation indicate that the rock-forming process is dominated by mixed crystallization. Ac-cording to the analysis on the rock-forming order, magmatic source, tectonic setting and rock-forming process, com-bined with the achievements of regional rock-controlling structures and division of sublayer of crust, it is believedthat Fenghuangshan rock body derives from the deep-seated alkalic basalt magma. The rock-forming process has un-dertaken sialic and calcareous assimilation and contamination of two different degrees. The rock-forming model be-longs to the typical assimilation and fractional cryatalization mechanism.展开更多
基金the National "973" Project (No. G1999043206) the National Scientific Project for Tackcling Key Problems(No. 2001BA609A-06-02).
文摘Based on the detailed geological investigation and record of galleries and drill holes, a new idea has beenadvanced that granodiorite is earlier than quartz monzodiorite porphyry. Both of them are products of two differentmagmatic intrusive activities. The analysis results of trace elements show that the Sr content is beyond any othercrustal rock and the Th content is beyond that of Ta. The whole-rock analysis indicates that rockbody is rich in CaOand poor in K2O. In the composition of Pb istope of rockbody, the ratio of 207Pb to 204Pb is less than 15.60. Allthese show that the magma mainly comes from the upper mantle. Ti,Zr,Cr,Nb trace elements and the relation be-tween the Gardini index(τ) and the Rittmann index(σ) indicate that the rockbodies are formed in the orogenic beltand island arc tectonic setting. The summation (∑REE) and the characteristic value (m (La)/m (Yb)) of the rareearth elements show that the original rock is alkalic basalt. The analysis of the characteristic values of REE and thequantitative modeling calculation indicate that the rock-forming process is dominated by mixed crystallization. Ac-cording to the analysis on the rock-forming order, magmatic source, tectonic setting and rock-forming process, com-bined with the achievements of regional rock-controlling structures and division of sublayer of crust, it is believedthat Fenghuangshan rock body derives from the deep-seated alkalic basalt magma. The rock-forming process has un-dertaken sialic and calcareous assimilation and contamination of two different degrees. The rock-forming model be-longs to the typical assimilation and fractional cryatalization mechanism.
