LA-ICP-MS zircon U-Pb dating indicates that the weighted average age of diorite from Nangnimsan,Mohe in the northern Da Hinggan Mountains in Heilongjiang Province is 516.2±1.7 Ma,as a result of magmatic intrusion...LA-ICP-MS zircon U-Pb dating indicates that the weighted average age of diorite from Nangnimsan,Mohe in the northern Da Hinggan Mountains in Heilongjiang Province is 516.2±1.7 Ma,as a result of magmatic intrusion of Early Cambrian. Geochemistry analysis indicates that the rocks belong to high-K calc-alkaline series,with low content of SiO_2( 52.24%-53.64%) and high Mg( MgO = 5.67%-6.56%,Mg~#= 61. 05-65. 46).The rocks are characterized by the enrichment of LREE and LILE( e.g. Rb,Ba,Pb),and relative depletion in HREE and HFSE( e.g. Ta,Nb,P,Ti),and with a high content of Sr( 442. 3-622. 3) × 10^(-6),Yb( 2.49-3.42) ×10^(-6) and Y( 25.64-35.49) ×10^(-6),and slightly negative Eu anormaly( δEu= 0.60-0.81). Based on Rb/Sr( 0.15-0.25) and Rb/Nb( 8.27-15.12),it is concluded that the primary magma of diorite was derived from the mixture of the crust and mantle. Combined with background of regional tectonic evolution,it is suggested that diorite was formed in the extensional environment after the collage of the EGM with the Siberian.展开更多
Zircon U-Pb dating, whole-rock geochemical analyses and Hf isotope are undertaken for the monzogranite in Niubiziliang area with the aim of constraining its formation time,petrogenesis and the regional tectonic settin...Zircon U-Pb dating, whole-rock geochemical analyses and Hf isotope are undertaken for the monzogranite in Niubiziliang area with the aim of constraining its formation time,petrogenesis and the regional tectonic setting. The zircons from monzogranite are euhedral-subhedral in shape,and display rhythm growth zoning,indicating a magmatic origin. LA-ICP-MS zircon U-Pb dating indicates the monzogranite formed most probably in the Late Devonian( 359. 0 ± 2. 6 Ma). The monzogranite has Si O2= 74. 69%--76. 11%,Al2O3=12. 07%--12. 81%,Na2 O + K2 O = 8. 24%--8. 70%,Na2 O / K2 O = 0. 60--0. 68,A / CNK > 1,which shows that it belongs to high-Si and high-K weakly peraluminous calc-alkaline series. The monzogranite is enriched in K,Rb,Th( LILEs) and La,Ce,Sm,Nd( LREEs); and depleted in Ba,U( HREEs) and Ta,Nb( HFSEs).Their zircon εHf( t) values range from 1. 21 to 3. 46,in response to their two-stage Hf model ages( TDM2) ranging from 1 034 Ma to 1 159 Ma,respectively,indicating that the primary magma was derived from the young crust in Meso-Neoproterozoic. Combined with the regional geological evolution background,it is considered that the Niubiziliang monzogranite formed the closure of North Qaidam ocean,which was the stretching stage product after the collision between Qaidam block and Qilian block.展开更多
The study presents the results of U-Pb dating of zircons and whole-rock geochemical analyses of a syenogranite located in the western Niubiziliang area,China with the aim of determining its formation time,petrogenesis...The study presents the results of U-Pb dating of zircons and whole-rock geochemical analyses of a syenogranite located in the western Niubiziliang area,China with the aim of determining its formation time,petrogenesis and the regional tectonic setting. Zircons within the syenogranite are euhedral-subhedral and display rhythmic growth zoning,indicating a magmatic origin. Zircon U-Pb data obtained by LA-ICP-MS indicate the syenogranite formed in the Late Permian (260.7±1.5 Ma). The w(SiO_2) of syenogranites is 70.82%--73.59%,w(Al_2O_3) is 13.49%--14.82%,and w(Na_2O + K_2O) is 7.85%--8.52%,and yield K_2O/Na_2O ratios of 1.06--1.26. Therefore,the syenogranites belong to the high-K calc-alkaline and metaluminous (A/CNK< 1,A/NK > 1) series which display I-type granites similarly. The syenogranites also show the geochemical characteristics of volcanic arc rocks,being enriched in large-ion lithophile elements (LILEs; K,Rb) and light rare-earth elements (LREEs; La,Ce,Sm,Nd),but depleted in high field strength elements( HFSEs; Ta,Nb,P,Ti). On the whole,trace element ratios are close to the mean of the Earth's crust,indicating a lowercrust magma source. The low Sr (161--214) ×10^(-6) and Yb (1.08--1.80)×10^(-6) concentrations indicate that plagioclase and hornblende are residual mineral phases in the source. The regional geology and whole-rock geochemistry suggest that the formation of the syenogranites was related to subduction of the Zongwulong Ocean crust,and the north margin of Qaidam Block during the Late Permian was in an active continental margin tectonic setting.展开更多
基金Supported by Project of China Geological Survey(No.12120113098300)
文摘LA-ICP-MS zircon U-Pb dating indicates that the weighted average age of diorite from Nangnimsan,Mohe in the northern Da Hinggan Mountains in Heilongjiang Province is 516.2±1.7 Ma,as a result of magmatic intrusion of Early Cambrian. Geochemistry analysis indicates that the rocks belong to high-K calc-alkaline series,with low content of SiO_2( 52.24%-53.64%) and high Mg( MgO = 5.67%-6.56%,Mg~#= 61. 05-65. 46).The rocks are characterized by the enrichment of LREE and LILE( e.g. Rb,Ba,Pb),and relative depletion in HREE and HFSE( e.g. Ta,Nb,P,Ti),and with a high content of Sr( 442. 3-622. 3) × 10^(-6),Yb( 2.49-3.42) ×10^(-6) and Y( 25.64-35.49) ×10^(-6),and slightly negative Eu anormaly( δEu= 0.60-0.81). Based on Rb/Sr( 0.15-0.25) and Rb/Nb( 8.27-15.12),it is concluded that the primary magma of diorite was derived from the mixture of the crust and mantle. Combined with background of regional tectonic evolution,it is suggested that diorite was formed in the extensional environment after the collage of the EGM with the Siberian.
文摘Zircon U-Pb dating, whole-rock geochemical analyses and Hf isotope are undertaken for the monzogranite in Niubiziliang area with the aim of constraining its formation time,petrogenesis and the regional tectonic setting. The zircons from monzogranite are euhedral-subhedral in shape,and display rhythm growth zoning,indicating a magmatic origin. LA-ICP-MS zircon U-Pb dating indicates the monzogranite formed most probably in the Late Devonian( 359. 0 ± 2. 6 Ma). The monzogranite has Si O2= 74. 69%--76. 11%,Al2O3=12. 07%--12. 81%,Na2 O + K2 O = 8. 24%--8. 70%,Na2 O / K2 O = 0. 60--0. 68,A / CNK > 1,which shows that it belongs to high-Si and high-K weakly peraluminous calc-alkaline series. The monzogranite is enriched in K,Rb,Th( LILEs) and La,Ce,Sm,Nd( LREEs); and depleted in Ba,U( HREEs) and Ta,Nb( HFSEs).Their zircon εHf( t) values range from 1. 21 to 3. 46,in response to their two-stage Hf model ages( TDM2) ranging from 1 034 Ma to 1 159 Ma,respectively,indicating that the primary magma was derived from the young crust in Meso-Neoproterozoic. Combined with the regional geological evolution background,it is considered that the Niubiziliang monzogranite formed the closure of North Qaidam ocean,which was the stretching stage product after the collision between Qaidam block and Qilian block.
文摘The study presents the results of U-Pb dating of zircons and whole-rock geochemical analyses of a syenogranite located in the western Niubiziliang area,China with the aim of determining its formation time,petrogenesis and the regional tectonic setting. Zircons within the syenogranite are euhedral-subhedral and display rhythmic growth zoning,indicating a magmatic origin. Zircon U-Pb data obtained by LA-ICP-MS indicate the syenogranite formed in the Late Permian (260.7±1.5 Ma). The w(SiO_2) of syenogranites is 70.82%--73.59%,w(Al_2O_3) is 13.49%--14.82%,and w(Na_2O + K_2O) is 7.85%--8.52%,and yield K_2O/Na_2O ratios of 1.06--1.26. Therefore,the syenogranites belong to the high-K calc-alkaline and metaluminous (A/CNK< 1,A/NK > 1) series which display I-type granites similarly. The syenogranites also show the geochemical characteristics of volcanic arc rocks,being enriched in large-ion lithophile elements (LILEs; K,Rb) and light rare-earth elements (LREEs; La,Ce,Sm,Nd),but depleted in high field strength elements( HFSEs; Ta,Nb,P,Ti). On the whole,trace element ratios are close to the mean of the Earth's crust,indicating a lowercrust magma source. The low Sr (161--214) ×10^(-6) and Yb (1.08--1.80)×10^(-6) concentrations indicate that plagioclase and hornblende are residual mineral phases in the source. The regional geology and whole-rock geochemistry suggest that the formation of the syenogranites was related to subduction of the Zongwulong Ocean crust,and the north margin of Qaidam Block during the Late Permian was in an active continental margin tectonic setting.
