Lead isotopic analytic data of 30 ores gathered from the Zhuanmiao boron deposit, Wengquangou boron (iron) deposit and its Dongtaizi Ore Member constitute three isochrons, the corresponding ages of which are 1902 ...Lead isotopic analytic data of 30 ores gathered from the Zhuanmiao boron deposit, Wengquangou boron (iron) deposit and its Dongtaizi Ore Member constitute three isochrons, the corresponding ages of which are 1902 ± 12 Ma, 1852 ± 9 Ma and 1917 ± 48 Ma. Lead isotopic analyses of marble from the Xiquegou Member of the Qingchenzi orefield yield a Pb-Pb isochron age of 1844 ± 27 Ma. 40Ar-39Ar quick neutron activation dating of phlogopites and microclines coexisting with ore minerals in the Wengquangou boron (iron) and Zhuanmiao boron deposits shows that: (1) the phlogopite from the Wengquangou has a plateau age of 1923 ± 1.5 Ma and an isochron age of 1924 ± 2.5 Ma; (2) the microcline from the Wengquangou has the plateau age of 1407 ± 5.4 Ma and 220 ± 12 Ma and an isochron age of 1403 ± 19 Ma; (3) the phlogopites from the Zhuanmiao yield a plateau age 1918 ± 1.3 Ma and an isochron age of 1918 ± 2.9 Ma; (4) the microclines from the Zhuanmiao yield the plateau age of 1420 ± 16 Ma and 250 ± 8 Ma and an isochron age of 1425 ± 19 Ma and 269 ± 16 Ma. These ages indicate that the eastern Liaoning area happened around 1900 Ma, an important tectonomagmatic event, which is consistent with the worldwide Mid-Proterozoic tectonomagmatic event. During this period, the Proterozoic Liaohe Group was folded and underwent strong normal metamorphism, and the (hydrothermal) sedimentary boron deposits (or source beds) formed earlier were strongly superimposed by mineralization, resulting in enrichment of boron; later regional geological processes made little contribution to the formation of the boron deposits. Lead isotopic components show that the U-Pb and Th-Pb isotopic system reached homogenization in the ores whereas only the U-Pb isotopic system reached homogenization in the marble from the Xiquegou district, which indicates that the boron deposits superimposed in the studied area endured a relatively strong process of hydrothermal migmatization during the end phase of early Proterozoic metamorphism.展开更多
In the early Proterozoic the Li'eryu Formation and Dashiqiao Formation of eastern Liaoning province, China, there are distributed Mg-rich carbonate rock formations, in which large to superlarge deposits of boron, ...In the early Proterozoic the Li'eryu Formation and Dashiqiao Formation of eastern Liaoning province, China, there are distributed Mg-rich carbonate rock formations, in which large to superlarge deposits of boron, magnesite, talc, Xiuyan jade etc. occur. The formation of these magnesian nonmetallic deposits was related to early Proterozoic evaporates; then these deposits underwent reworking of regional metamorphism and hydrothermal metasomatism during the Lüliang orogeny and tectono-magmatism during the Indosinian-Yanshanian. Among other things, the Mg-rich carbonates formations, minerogenetic structures and ore-forming fluids played a controlling role in the formation of the mineral deposits. Therefore, it can be concluded that the mineral deposits are products of combined processes of the coupling of ore source field, fluid field, thermal field (energy field) and stress field under certain time-space conditions in the early Proterozoic and the late-stage superimposed reworking of tectono-magmatism.展开更多
This paper focused on the zircon sensitive high resolution ion micro-probeU-Pb geochronology of the tourmalinites from boron-bearing series of borate deposits in Eastern Liaoning. The zircons commonly have core-rim st...This paper focused on the zircon sensitive high resolution ion micro-probeU-Pb geochronology of the tourmalinites from boron-bearing series of borate deposits in Eastern Liaoning. The zircons commonly have core-rim structures, most cores show oscillatory zoning in cathodoluminescence and plane polarized light images, suggesting a magmatic detrital origin. Ages of the magmatic detrital zircons from the hyalotonrmalite samples （N13） and （N14） are 2175 ± 5 Ma and 2171 ± 9 Ma, respectively. Moreover, metamorphic zircon from the sample （N13） shows an age of 1906 ± 4 Ma. Zircon core and rim from the hyalotourmalite sample （N02） record ages of 2171 ± 6 Ma and 1889± 62 Ma, which are explained as indicating the formation and metamorphic ages. Combined with the geological and geochemical studies, it can be concluded that the tourmalinites are formed during sedimentary exhalative mineralizations in the mid-Paleoproterozoic （-170 Ma） and underwent the metamorphism in the late-Paleoproterozoic （-1900 Ma）. The tourmalinites are the products of submarine acid volcanism in the extension rifting phase of the Liaoji Paleoproterozoic Rift, the rockforming materials of which are derived from the mantle sources with recycling crustal contamination. The emergence of tourmalinites not only indicates the mid-Paleoproterozoic tectonic-magmatic processes, but also provides impetus, heat and material sources for the mineralization of borate deposits in Eastern Liaoning.展开更多
The late Neoarchean metamorphosed volcanic rocks in the southern Liaoning Terrane(SLT) of the eastern North China Craton(NCC) are mainly composed of amphibolites and felsic gneisses and can be chemically classified as...The late Neoarchean metamorphosed volcanic rocks in the southern Liaoning Terrane(SLT) of the eastern North China Craton(NCC) are mainly composed of amphibolites and felsic gneisses and can be chemically classified as basalt(Group#1),basaltic andesite(Group#2),dacite(Group#3) and rhyodacite(Group#4).LA-ICP-MS zircon U-Th-Pb dating reveals that they formed at ~2.53-2.51 Ga.Group#1 samples are characterized by approximately flat chondrite-normalized rare earth element(REE) patterns with low(La/Yb)_N ratios and a narrow range of(Hf/Sm)N ratios,and their magmatic precursors were generated by partial melting of a depleted mantle wedge weakly metasomatized by subducted slab fluids.Compared to Group#1 samples,Group#2 samples display strongly fractionated REE patterns with higher(La/Yb)_N ratios and more scattered(Hf/Sm)N ratios,indicative of a depleted mantle wedge that had been intensely metasomatized by slab-derived melts and fluids.Group#3 samples are characterized by high MgO and transition trace element concentrations and fractionated REE patterns,which resemble typical high-Si adakites,and the magmatic precursors were derived from partial melting of a subducted oceanic slab.Group#4 samples have the highest SiO_2 and the lowest MgO and transition trace element contents,and were derived from partial melting of basaltic rocks at lower crust levels.Integrating these tholeiitic to calcalkaline volcanic rocks with the mass of contemporaneous dioritic-tonalitic-trondhjemitic-granodioritic gneisses,the late Neoarchean volcanic rocks in the SLT were most likely produced in an active continental margin.Furthermore,the affinities in lithological assemblages,metamorphism and tectonic regime among SLT,eastern Hebei to western Liaoning Terrane(EH-WLT),northern Liaoning to southern Jilin Terrane(NL-SJT),AnshanBenxi continental nucleus(ABN) and Yishui complex(YSC) collectively indicate that an integral and much larger continental block had been formed in the late Neoarchean and the craton-scale lateral accretion was a dominantly geodynamic mechanism in the eastern NCC.展开更多
The Xiaotongjiapuzi gold deposit occurs in a Palaeoproterozoic rift accretionary terrane in eastern Liaoning and is hosted by a carbonate formation of the Dashiqiao Formation, Liaohe Group. The metamorphic grade of th...The Xiaotongjiapuzi gold deposit occurs in a Palaeoproterozoic rift accretionary terrane in eastern Liaoning and is hosted by a carbonate formation of the Dashiqiao Formation, Liaohe Group. The metamorphic grade of the host rock is low amphibolite-high greenschist facies. Gold, which is mainly invisible, is distributed in pyrite and arsenopyrite. The grains of Au-bearing sulphide minerals are fine, ranging from 0.0 n to 1 mm. The wall-rock alterations are characterized by low-temperature silification, hydro-sericitization, sericitization and carbonatization. The homogenization temperatures of the fluid inclusions in quartz closely associated with gold mineralization range from 140 to 240°C. The metallogenic age represented by the Ar-Ar isotopic age of sericite is 167 Ma. Comparisons and studies show that the Xiaotongjiapuzi gold deposit can be classified as the submicron-sized disseminated deposit (analogous to the Carlin-type) hosted in metamorphic rocks.展开更多
Objective The Liao-Ji orogenic belt is a famous Paleoproterozoic orogenic belt in the East Block of the North China Craton(NCC),which extend in NE-SW direction.The geological mass in the Paleoproterozoic Liao-Ji belt ...Objective The Liao-Ji orogenic belt is a famous Paleoproterozoic orogenic belt in the East Block of the North China Craton(NCC),which extend in NE-SW direction.The geological mass in the Paleoproterozoic Liao-Ji belt is mainly composed of the Liaoji granites and metamorphic volcanic-sedimentary rocks of the Liaohe group(and its展开更多
Objective The Jehol biota refers to a flora and fauna that thrived in the Early Cretaceous (Shao Tiequan et al., 2017), and Eosestheria is an important component of the Jehol biota and is also an important link in the...Objective The Jehol biota refers to a flora and fauna that thrived in the Early Cretaceous (Shao Tiequan et al., 2017), and Eosestheria is an important component of the Jehol biota and is also an important link in the biota chain during its production period.展开更多
Gold deposits in eastern Liaoning, northeast China are hosted in the middle and upper parts of a Paleoproterozoic volcanic-sedimentary succession, which consists of interlayered carbonates and fine-grained clastics. T...Gold deposits in eastern Liaoning, northeast China are hosted in the middle and upper parts of a Paleoproterozoic volcanic-sedimentary succession, which consists of interlayered carbonates and fine-grained clastics. This paper discusses the geological features of ore-bearing formations, ore-controlling structures and metallogenetic characteristics. Analysis of ore-controlling factors suggested that the schists from the Gaixian formatyion, syngenetic faults and ductile shear zones are principal ore controls over mineralization and thereafter indicators for gold exploration.展开更多
Accurately determining the age of the Tuchengzi Formation has direct influence on confirming the boundary between the Jurassic and the Cretaceous systems in northern Hebei-western Liaoning, and on related geological p...Accurately determining the age of the Tuchengzi Formation has direct influence on confirming the boundary between the Jurassic and the Cretaceous systems in northern Hebei-western Liaoning, and on related geological problems in China. However, the Tuchengzi Formation mainly consists of sedi-mentary rocks, with a poor fossil record and especially lack of index fossils. The Tuchengzi Formation is also lack of the type of volcanic rocks that can provide an isotopic age. Therefore, the age of the Tuchengzi Formation has been uncertain. Based on our systematic dating of the tuff interbedded in the Tuchengzi Formation of Chengde and Jinlingsi-Yangshan basins in northern Hebei-western Liaoning, combined with the dating results of previous researchers, here we suggest that the age range of the Tuchengzi Formation in northern Hebei-western Liaoning is from 147 Ma to 136 Ma. It implied that the Tuchengzi Formation was mainly formed in the Early Cretaceous.展开更多
Molar tooth(briefly called MT) carbonate is one of the Proterozoic carbonates with enigmatic sedimentary structure. According to the morphology of MT,it can be divided into two main genesis-morphology types,i.e.,autoc...Molar tooth(briefly called MT) carbonate is one of the Proterozoic carbonates with enigmatic sedimentary structure. According to the morphology of MT,it can be divided into two main genesis-morphology types,i.e.,autochthonous and allochthonous,and each type can be further divided into a series of subtypes. The autochthonous MT can be divided into filamentous(MF1) ,ribbon,nodular and dotted type(MF4) ,in which the ribbon one can be subdivided into simple vertical(MF2) and complex ribbon(MF3) ,broken ribbon by storm in situ(MF5) and MT within nodular limestone(MF6) . Allochthonous MT includes conglomerate clasts and horizontal detritus. Studying on the links between MT and the host rocks on five stratigraphic sections in the southeastern Jilin and eastern Liaoning indicates that the morphology of MT is closely related to host rocks,and seven genetic types by relationships between MT and the host rocks with facies interpretations are classified and discussed in this paper. The sedimentary environments of MT formation will be diverse if their morphologies are different.展开更多
There are large to superlarge magnesite and talc deposits occurring in Mg-rich carbonate formations distributed in the early Proterozoic Dashiqiao Formation in eastern Liaoning Province, China. The discovery of the se...There are large to superlarge magnesite and talc deposits occurring in Mg-rich carbonate formations distributed in the early Proterozoic Dashiqiao Formation in eastern Liaoning Province, China. The discovery of the sedimentary gypsum, isotopic geochemistry of Δ18osmow, Δ13cpdb, Δ34svcdt and Sr/Ba ratio of carbonate, talc, quartz and gypsums with field investigation and sample analysis in laboratory demonstrate that the formation of magnesite and talc deposits is closely related to marine evaporates, which then underwent reworking of regional metamorphism and hydrothermal metasomatism. Metasomatic fluids originating from the paleoseawater played a controlling role in the formation of talc deposits.展开更多
Chaotiehe gabbroic intrusion in the eastern part of Liaoning Province was dated by the zircon SHRIMP U-Pb technique. The results gave an emplacement age of 126±4 Ma, indicating that the intrusion thus formed duri...Chaotiehe gabbroic intrusion in the eastern part of Liaoning Province was dated by the zircon SHRIMP U-Pb technique. The results gave an emplacement age of 126±4 Ma, indicating that the intrusion thus formed during the lithospheric thinning of the North China Craton (NCC) in the Early Cretaceous rather than in a rifting setting during the Paleoproterozoic as previously thought. The gabbroic intrusion contains abundant old zircons with Paleoproterozoic (2.10-2.46 Ga and ca. 1.87 Ga) and Neoproterozoic (747-969 Ma) ages. The Paleoproterozoic zircons were probably derived from NCC itself, whereas the Neoproterozoic ones were likely from materials of the Yangtze Craton that had previously been subducted beneath NCC. These geochronological dates are of important implications for understanding the Mesozoic crustal evolution of NCC.展开更多
基金supported by the National 973 Project of China(G1999043201)
文摘Lead isotopic analytic data of 30 ores gathered from the Zhuanmiao boron deposit, Wengquangou boron (iron) deposit and its Dongtaizi Ore Member constitute three isochrons, the corresponding ages of which are 1902 ± 12 Ma, 1852 ± 9 Ma and 1917 ± 48 Ma. Lead isotopic analyses of marble from the Xiquegou Member of the Qingchenzi orefield yield a Pb-Pb isochron age of 1844 ± 27 Ma. 40Ar-39Ar quick neutron activation dating of phlogopites and microclines coexisting with ore minerals in the Wengquangou boron (iron) and Zhuanmiao boron deposits shows that: (1) the phlogopite from the Wengquangou has a plateau age of 1923 ± 1.5 Ma and an isochron age of 1924 ± 2.5 Ma; (2) the microcline from the Wengquangou has the plateau age of 1407 ± 5.4 Ma and 220 ± 12 Ma and an isochron age of 1403 ± 19 Ma; (3) the phlogopites from the Zhuanmiao yield a plateau age 1918 ± 1.3 Ma and an isochron age of 1918 ± 2.9 Ma; (4) the microclines from the Zhuanmiao yield the plateau age of 1420 ± 16 Ma and 250 ± 8 Ma and an isochron age of 1425 ± 19 Ma and 269 ± 16 Ma. These ages indicate that the eastern Liaoning area happened around 1900 Ma, an important tectonomagmatic event, which is consistent with the worldwide Mid-Proterozoic tectonomagmatic event. During this period, the Proterozoic Liaohe Group was folded and underwent strong normal metamorphism, and the (hydrothermal) sedimentary boron deposits (or source beds) formed earlier were strongly superimposed by mineralization, resulting in enrichment of boron; later regional geological processes made little contribution to the formation of the boron deposits. Lead isotopic components show that the U-Pb and Th-Pb isotopic system reached homogenization in the ores whereas only the U-Pb isotopic system reached homogenization in the marble from the Xiquegou district, which indicates that the boron deposits superimposed in the studied area endured a relatively strong process of hydrothermal migmatization during the end phase of early Proterozoic metamorphism.
基金supported by the Foundation for Development of Geological Science and Technology of the former Ministry of Geology and Mineral Resources of China grant HY979830
文摘In the early Proterozoic the Li'eryu Formation and Dashiqiao Formation of eastern Liaoning province, China, there are distributed Mg-rich carbonate rock formations, in which large to superlarge deposits of boron, magnesite, talc, Xiuyan jade etc. occur. The formation of these magnesian nonmetallic deposits was related to early Proterozoic evaporates; then these deposits underwent reworking of regional metamorphism and hydrothermal metasomatism during the Lüliang orogeny and tectono-magmatism during the Indosinian-Yanshanian. Among other things, the Mg-rich carbonates formations, minerogenetic structures and ore-forming fluids played a controlling role in the formation of the mineral deposits. Therefore, it can be concluded that the mineral deposits are products of combined processes of the coupling of ore source field, fluid field, thermal field (energy field) and stress field under certain time-space conditions in the early Proterozoic and the late-stage superimposed reworking of tectono-magmatism.
基金supported by the National Natural Science Foundation of China grant(40073013)
文摘This paper focused on the zircon sensitive high resolution ion micro-probeU-Pb geochronology of the tourmalinites from boron-bearing series of borate deposits in Eastern Liaoning. The zircons commonly have core-rim structures, most cores show oscillatory zoning in cathodoluminescence and plane polarized light images, suggesting a magmatic detrital origin. Ages of the magmatic detrital zircons from the hyalotonrmalite samples （N13） and （N14） are 2175 ± 5 Ma and 2171 ± 9 Ma, respectively. Moreover, metamorphic zircon from the sample （N13） shows an age of 1906 ± 4 Ma. Zircon core and rim from the hyalotourmalite sample （N02） record ages of 2171 ± 6 Ma and 1889± 62 Ma, which are explained as indicating the formation and metamorphic ages. Combined with the geological and geochemical studies, it can be concluded that the tourmalinites are formed during sedimentary exhalative mineralizations in the mid-Paleoproterozoic （-170 Ma） and underwent the metamorphism in the late-Paleoproterozoic （-1900 Ma）. The tourmalinites are the products of submarine acid volcanism in the extension rifting phase of the Liaoji Paleoproterozoic Rift, the rockforming materials of which are derived from the mantle sources with recycling crustal contamination. The emergence of tourmalinites not only indicates the mid-Paleoproterozoic tectonic-magmatic processes, but also provides impetus, heat and material sources for the mineralization of borate deposits in Eastern Liaoning.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.41530207 and 41772188)。
文摘The late Neoarchean metamorphosed volcanic rocks in the southern Liaoning Terrane(SLT) of the eastern North China Craton(NCC) are mainly composed of amphibolites and felsic gneisses and can be chemically classified as basalt(Group#1),basaltic andesite(Group#2),dacite(Group#3) and rhyodacite(Group#4).LA-ICP-MS zircon U-Th-Pb dating reveals that they formed at ~2.53-2.51 Ga.Group#1 samples are characterized by approximately flat chondrite-normalized rare earth element(REE) patterns with low(La/Yb)_N ratios and a narrow range of(Hf/Sm)N ratios,and their magmatic precursors were generated by partial melting of a depleted mantle wedge weakly metasomatized by subducted slab fluids.Compared to Group#1 samples,Group#2 samples display strongly fractionated REE patterns with higher(La/Yb)_N ratios and more scattered(Hf/Sm)N ratios,indicative of a depleted mantle wedge that had been intensely metasomatized by slab-derived melts and fluids.Group#3 samples are characterized by high MgO and transition trace element concentrations and fractionated REE patterns,which resemble typical high-Si adakites,and the magmatic precursors were derived from partial melting of a subducted oceanic slab.Group#4 samples have the highest SiO_2 and the lowest MgO and transition trace element contents,and were derived from partial melting of basaltic rocks at lower crust levels.Integrating these tholeiitic to calcalkaline volcanic rocks with the mass of contemporaneous dioritic-tonalitic-trondhjemitic-granodioritic gneisses,the late Neoarchean volcanic rocks in the SLT were most likely produced in an active continental margin.Furthermore,the affinities in lithological assemblages,metamorphism and tectonic regime among SLT,eastern Hebei to western Liaoning Terrane(EH-WLT),northern Liaoning to southern Jilin Terrane(NL-SJT),AnshanBenxi continental nucleus(ABN) and Yishui complex(YSC) collectively indicate that an integral and much larger continental block had been formed in the late Neoarchean and the craton-scale lateral accretion was a dominantly geodynamic mechanism in the eastern NCC.
文摘The Xiaotongjiapuzi gold deposit occurs in a Palaeoproterozoic rift accretionary terrane in eastern Liaoning and is hosted by a carbonate formation of the Dashiqiao Formation, Liaohe Group. The metamorphic grade of the host rock is low amphibolite-high greenschist facies. Gold, which is mainly invisible, is distributed in pyrite and arsenopyrite. The grains of Au-bearing sulphide minerals are fine, ranging from 0.0 n to 1 mm. The wall-rock alterations are characterized by low-temperature silification, hydro-sericitization, sericitization and carbonatization. The homogenization temperatures of the fluid inclusions in quartz closely associated with gold mineralization range from 140 to 240°C. The metallogenic age represented by the Ar-Ar isotopic age of sericite is 167 Ma. Comparisons and studies show that the Xiaotongjiapuzi gold deposit can be classified as the submicron-sized disseminated deposit (analogous to the Carlin-type) hosted in metamorphic rocks.
基金supported by the National Science Foundation of China (grant No. 41272223)China Geological Survey (grants No. DD20160049, 1212011220247 and 12120110300015)
文摘Objective The Liao-Ji orogenic belt is a famous Paleoproterozoic orogenic belt in the East Block of the North China Craton(NCC),which extend in NE-SW direction.The geological mass in the Paleoproterozoic Liao-Ji belt is mainly composed of the Liaoji granites and metamorphic volcanic-sedimentary rocks of the Liaohe group(and its
基金Funding was provided by the sub-project of "Geological and Mineral Survey Project of the Metallogenic Belt of Eastern Liaodong and Southern Jilin" of China Geological Survey (grant No. 1212011120733)
文摘Objective The Jehol biota refers to a flora and fauna that thrived in the Early Cretaceous (Shao Tiequan et al., 2017), and Eosestheria is an important component of the Jehol biota and is also an important link in the biota chain during its production period.
文摘Gold deposits in eastern Liaoning, northeast China are hosted in the middle and upper parts of a Paleoproterozoic volcanic-sedimentary succession, which consists of interlayered carbonates and fine-grained clastics. This paper discusses the geological features of ore-bearing formations, ore-controlling structures and metallogenetic characteristics. Analysis of ore-controlling factors suggested that the schists from the Gaixian formatyion, syngenetic faults and ductile shear zones are principal ore controls over mineralization and thereafter indicators for gold exploration.
基金Supported by National Natural Science Foundation of China (Grant No. 90714010)
文摘Accurately determining the age of the Tuchengzi Formation has direct influence on confirming the boundary between the Jurassic and the Cretaceous systems in northern Hebei-western Liaoning, and on related geological problems in China. However, the Tuchengzi Formation mainly consists of sedi-mentary rocks, with a poor fossil record and especially lack of index fossils. The Tuchengzi Formation is also lack of the type of volcanic rocks that can provide an isotopic age. Therefore, the age of the Tuchengzi Formation has been uncertain. Based on our systematic dating of the tuff interbedded in the Tuchengzi Formation of Chengde and Jinlingsi-Yangshan basins in northern Hebei-western Liaoning, combined with the dating results of previous researchers, here we suggest that the age range of the Tuchengzi Formation in northern Hebei-western Liaoning is from 147 Ma to 136 Ma. It implied that the Tuchengzi Formation was mainly formed in the Early Cretaceous.
基金Supported by the National Natural Scientific Foundation of China (Grant No. 40772078)International Geological Correlation Program (IGCP447), (Grant No. SC/GEO/546/447)+1 种基金Foundation of Geology Iustitute, CAGS (Grant No. J0903)Natural Scientific Development Foundation of Yangtze University (Grant No. 2007ZP005)
文摘Molar tooth(briefly called MT) carbonate is one of the Proterozoic carbonates with enigmatic sedimentary structure. According to the morphology of MT,it can be divided into two main genesis-morphology types,i.e.,autochthonous and allochthonous,and each type can be further divided into a series of subtypes. The autochthonous MT can be divided into filamentous(MF1) ,ribbon,nodular and dotted type(MF4) ,in which the ribbon one can be subdivided into simple vertical(MF2) and complex ribbon(MF3) ,broken ribbon by storm in situ(MF5) and MT within nodular limestone(MF6) . Allochthonous MT includes conglomerate clasts and horizontal detritus. Studying on the links between MT and the host rocks on five stratigraphic sections in the southeastern Jilin and eastern Liaoning indicates that the morphology of MT is closely related to host rocks,and seven genetic types by relationships between MT and the host rocks with facies interpretations are classified and discussed in this paper. The sedimentary environments of MT formation will be diverse if their morphologies are different.
文摘There are large to superlarge magnesite and talc deposits occurring in Mg-rich carbonate formations distributed in the early Proterozoic Dashiqiao Formation in eastern Liaoning Province, China. The discovery of the sedimentary gypsum, isotopic geochemistry of Δ18osmow, Δ13cpdb, Δ34svcdt and Sr/Ba ratio of carbonate, talc, quartz and gypsums with field investigation and sample analysis in laboratory demonstrate that the formation of magnesite and talc deposits is closely related to marine evaporates, which then underwent reworking of regional metamorphism and hydrothermal metasomatism. Metasomatic fluids originating from the paleoseawater played a controlling role in the formation of talc deposits.
基金supported by the National Natural Science Foundation of China (Grant No. 40773025)the Ministry of Science and Technology of China (Grant No. 2006CB403504)
文摘Chaotiehe gabbroic intrusion in the eastern part of Liaoning Province was dated by the zircon SHRIMP U-Pb technique. The results gave an emplacement age of 126±4 Ma, indicating that the intrusion thus formed during the lithospheric thinning of the North China Craton (NCC) in the Early Cretaceous rather than in a rifting setting during the Paleoproterozoic as previously thought. The gabbroic intrusion contains abundant old zircons with Paleoproterozoic (2.10-2.46 Ga and ca. 1.87 Ga) and Neoproterozoic (747-969 Ma) ages. The Paleoproterozoic zircons were probably derived from NCC itself, whereas the Neoproterozoic ones were likely from materials of the Yangtze Craton that had previously been subducted beneath NCC. These geochronological dates are of important implications for understanding the Mesozoic crustal evolution of NCC.
