Based on field observations and rheology analysis, we perform one analogue experiment and remold the 3D structural frame of Tongling deposit concentrating area firstly. Then we disassemble and dialyze the 3D structure...Based on field observations and rheology analysis, we perform one analogue experiment and remold the 3D structural frame of Tongling deposit concentrating area firstly. Then we disassemble and dialyze the 3D structures of the model using the methods of "slicing" and "stripping". A series of sliced planes vertical to the fold hinges show similar landscapes of that in the drill hole profiles. Meanwhile, layer stripping analysis indicates that the deformation features of each layer in the model are qualitatively analogical to those obtained from field observations. Through contrasting the 3D structure between the experimental model and the field phenomena, we verify the following 3D deformation features of the caprock in this area: (1) the Tongling area mainly consists of three series of NE S-typed fold groups; (2) in the uniform stress field, the incoherent folds universally develop in different positions, along different axes as well as in different strata; (3) the faults propagate upward which are mostly inter-bedded detachment faults, while the fold amplitudes decrease while going deeper; and (4) the folds and cleavages are highly developed in the Silurian System indicating that the deformation effect of the Indosin-ian-Yanshanian structural layer terminates at this layer, which suggests that the Silurian System is the crucial layer for the inversion between brittle and plastic deformation domains and the underlying strata are subject to the control of another deformation system with distinct properties.展开更多
The Xiaoban gold deposit is a large size deposit recently found in middle area of Fujian Province. It belongs to magmatic hydrothermal type occurred in Mayuan Group metamorphic rocks of Middle Proterozoic and is contr...The Xiaoban gold deposit is a large size deposit recently found in middle area of Fujian Province. It belongs to magmatic hydrothermal type occurred in Mayuan Group metamorphic rocks of Middle Proterozoic and is controlled by low angle fault (detachment) structures. The contents of Au in Mayuan Group metamorphic rocks, Caledonian Indosinian deformed granite and early Yanshanian granite are higher with Au enrichment coefficient of 2.06-5.68, 5.11 and 6.67 than those in other geological bodies. And the higher enrichment coefficients (>2) of Ag, S, Sn and Te are similar to those of gold ore. Meanwhile, the distribution of Au in Mayuan Group metamorphic rocks and early Yanshanian granite with a low D value (0.58 and 0.67) is favorable to gold mineralization. REE characteristics of gold ore, ratios of (LREE/HREE), (La/Sm) n, (Yb/Lu) n, (La/Tb) n and (Sm/Nd) n are similar to Mayuan Group metamorphic rocks, only non or little normal Eu abnormal of ore is dissimilar to metamorphic rocks. The δ ( 34 S) of the gold ore, with a high homogenization, is (-4.7×10 -3 )-(-2.7×10 -3 ). The study of inclusion indicates 180-249 ℃ of mineralization temperature, 3.69 %-11.81 % of salinities and 0.869-0.991 g/cm 3 of densities of mineralization fluid. Based on hydrogen and oxygen isotope ( δ ( 18 O)=11.0×10 -3 -11.7×10 -3 , δ (D)=(-48×10 -3 )-(-62×10 -3 )) and initial w ( 87 Sr)/ w ( 86 Sr) =0.715,combining to the analysis of geological history, regional metamorphism and magamtic activity, the authors confirm that the source for the ore fluid was mainly from magmatic, partly from metamorphic water, and with a little influence of meteoric water. Isotopic dating made on Rb Sr isochron age of 182 Ma, by using alteration minerals of gold ores from the deposit, indicates that the mineralization occurs in early Yanshanian epoch. This is close to the age of 187 Ma of the Anchun magmatite with a similar alteration and gold mineralization to the Xiaoban gold deposit. The age of early Yanshanian epoch of the Xiaoban gold is indentical with the characteristics of southern China gold metallogenic belt and the geotectonic evolution of the transition from paleo Asian system and paleo Tethyan system to paleo Pacific active continental margin in eastern Asia.展开更多
基金the National NaturalScience Foundation of China(Grant No.40234051)the Special Plansof Science and Technology of Land Resource Department(Grant No.20010103)+2 种基金the National Important Layout ltems of Basic ResearchDevelopment(Grant No.1999043206)the Fostering Plan Fund forBeyond-Century Excellent Talent the Key Project of Science and Technology Research(O3178)of the Ministry of Education.
文摘Based on field observations and rheology analysis, we perform one analogue experiment and remold the 3D structural frame of Tongling deposit concentrating area firstly. Then we disassemble and dialyze the 3D structures of the model using the methods of "slicing" and "stripping". A series of sliced planes vertical to the fold hinges show similar landscapes of that in the drill hole profiles. Meanwhile, layer stripping analysis indicates that the deformation features of each layer in the model are qualitatively analogical to those obtained from field observations. Through contrasting the 3D structure between the experimental model and the field phenomena, we verify the following 3D deformation features of the caprock in this area: (1) the Tongling area mainly consists of three series of NE S-typed fold groups; (2) in the uniform stress field, the incoherent folds universally develop in different positions, along different axes as well as in different strata; (3) the faults propagate upward which are mostly inter-bedded detachment faults, while the fold amplitudes decrease while going deeper; and (4) the folds and cleavages are highly developed in the Silurian System indicating that the deformation effect of the Indosin-ian-Yanshanian structural layer terminates at this layer, which suggests that the Silurian System is the crucial layer for the inversion between brittle and plastic deformation domains and the underlying strata are subject to the control of another deformation system with distinct properties.
文摘The Xiaoban gold deposit is a large size deposit recently found in middle area of Fujian Province. It belongs to magmatic hydrothermal type occurred in Mayuan Group metamorphic rocks of Middle Proterozoic and is controlled by low angle fault (detachment) structures. The contents of Au in Mayuan Group metamorphic rocks, Caledonian Indosinian deformed granite and early Yanshanian granite are higher with Au enrichment coefficient of 2.06-5.68, 5.11 and 6.67 than those in other geological bodies. And the higher enrichment coefficients (>2) of Ag, S, Sn and Te are similar to those of gold ore. Meanwhile, the distribution of Au in Mayuan Group metamorphic rocks and early Yanshanian granite with a low D value (0.58 and 0.67) is favorable to gold mineralization. REE characteristics of gold ore, ratios of (LREE/HREE), (La/Sm) n, (Yb/Lu) n, (La/Tb) n and (Sm/Nd) n are similar to Mayuan Group metamorphic rocks, only non or little normal Eu abnormal of ore is dissimilar to metamorphic rocks. The δ ( 34 S) of the gold ore, with a high homogenization, is (-4.7×10 -3 )-(-2.7×10 -3 ). The study of inclusion indicates 180-249 ℃ of mineralization temperature, 3.69 %-11.81 % of salinities and 0.869-0.991 g/cm 3 of densities of mineralization fluid. Based on hydrogen and oxygen isotope ( δ ( 18 O)=11.0×10 -3 -11.7×10 -3 , δ (D)=(-48×10 -3 )-(-62×10 -3 )) and initial w ( 87 Sr)/ w ( 86 Sr) =0.715,combining to the analysis of geological history, regional metamorphism and magamtic activity, the authors confirm that the source for the ore fluid was mainly from magmatic, partly from metamorphic water, and with a little influence of meteoric water. Isotopic dating made on Rb Sr isochron age of 182 Ma, by using alteration minerals of gold ores from the deposit, indicates that the mineralization occurs in early Yanshanian epoch. This is close to the age of 187 Ma of the Anchun magmatite with a similar alteration and gold mineralization to the Xiaoban gold deposit. The age of early Yanshanian epoch of the Xiaoban gold is indentical with the characteristics of southern China gold metallogenic belt and the geotectonic evolution of the transition from paleo Asian system and paleo Tethyan system to paleo Pacific active continental margin in eastern Asia.
