Meiling Wu | The University of Hong Kong (original) (raw)

Papers by Meiling Wu

Research paper thumbnail of Ages, geochemistry and metamorphism of the neoarchean basement in Shandong province

Research paper thumbnail of A synthesis of geochemistry and Sm–Nd isotopes of Archean granitoid gneisses in the Jiaodong Terrane: Constraints on petrogenesis and tectonic evolution of the Eastern Block, North China Craton

Precambrian Research, 2014

The Jiaodong Terrane is situated in the northeastern part of the Shandong Province in eastern Chi... more The Jiaodong Terrane is situated in the northeastern part of the Shandong Province in eastern China, experiencing multi-stage magmatism during the Mesoarchean (∼2.9 Ga) and Neoarchean (∼2.7 Ga and ∼2.5 Ga). It consists dominantly of granitoid gneisses with minor amphibolite enclaves or lenses. This study presents new whole-rock geochemical and Sm-Nd isotopic data for the Archean granitoid gneisses from the Jiaodong Terrane in order to constrain their petrogenesis and tectonic setting. Geochemical studies and petrological features suggest that the protoliths of most granitoid gneisses are typical Archean tonalitic-trondhjemitic-granodioritic (TTG) suites, which are high in SiO 2 (60.9-76.8 wt.%), Al 2 O 3 (12.6-16.8 wt.%), Na 2 O (3.3-5.3 wt.%), Sr (135-604 ppm) and Sr/Y ratios (13.9-84), but low in MgO (0.4-4.5 wt.%), K 2 O (0.7-3.4 wt.%), TiO 2 (0.2-0.9 wt.%), Cr (<0.5-37.9 ppm), Ni (<0.5-24 ppm), Y (2.8-19 ppm) and Mg number (Mg # = 30-45). They are generally enriched in light rare earth elements (LREE) and large ion lithophile elements (LILE), depleted in heavy rare earth elements (HREE) and high field strength elements (HFSE), with slight Eu anomalies. These geochemical features suggest that they were derived from partial melting of metabasaltic rocks leaving eclogite or garnet-amphibolite dominant in the residue. Whole-rock Nd isotopes reveal that the protoliths of Mesoarchean (∼2.9 Ga) granitoid gneisses were derived mainly from juvenile sources, whereas the early Neoarchean (∼2.7 Ga) granitoid gneisses were derived from juvenile sources with significant additions of crustal material and the late Neoarchean (∼2.5 Ga) granitoid gneisses were mainly derived from continental crustal sources. Combined with other geological considerations, a mantle plume model is favored to account for the generation of both early and late Neoarchean granitoid gneisses, whereas the tectonic setting for the Mesoarchean granitoid gneisses remains uncertain due to lack of geological data.

Research paper thumbnail of ZIRCON AGES, HF ISOTOPES AND PT PATH OF THE YISHUI COMPLEX: IMPLICATIONS FOR THE CRUST GROWTH AND TECTONOTHERMAL EVOLUTION OF THE EASTERN BLOCK OF THE NORTH CHINA CRATON

High-grade metamorphic supracrustal rocks and granitoids (TTG suites and charnockites) comprise t... more High-grade metamorphic supracrustal rocks and granitoids (TTG suites and charnockites) comprise the Yishui Complex, one of the major Neoarchean complexes in the Eastern Block of the North China Craton. New zircon dating results reveal the magmatic precursors of the supracrustal metapelites and TTG gneisses were generated at 2.58-2.53 Ga and 2.53-2.52 Ga, respectively, and the charnockites were emplaced around 2.58-2.53 Ga. The metamorphic single zircons and overgrowth rims document consistent metamorphic ages at ~2.50 Ga, suggesting the Yishui Complex experienced a regional metamorphism at the end of Neoarchean. Inherited detrital zircons yield ages between 3.0-2.6 Ga with a peak at 2.7-2.6 Ga, indicating the existence of Early Neoarchean magmatism in the Yishui area. Hf isotopic compositions show the Late Neoarchean zircons have positive εHf(t) values from +1.6 to +7.1, with depleted mantle model ages of 2.78-2.59 Ga, close to their crystallization ages. This suggests a significant crustal growth event at 2.8-2.6 Ga and the Neoarchean crust was predominantly derived from juvenile crustal sources with weak contributions of older crustal materials. A metamorphic study on mafic granulite enclaves has reveled three distinct mineral assemblages: the pre-peak assemblage (M1) of Hb + Pl + Qtz + Ilm + Mt occurring as inclusions within garnet and pyroxene, peak assemblage (M2) of Opx + Cpx + Pl + Grt + Hb + Qtz + Ilm + Mt, and post-peak assemblage (M3) represented by Grt + Qtz symplectites. Pseudosection modeling by THERMOCALC in the NCFMASHTO system for a representative mafic granulite constrains the P-T conditions of M1, M2 and M3 stages at 660-730°C/<6.6 kbar, 800-820°C/8.0-8.5 kbar and 686-710°C/7.6-8.6 kbar, respectively. The petrology and quantitative P-T pseudosection modeling define an anticlockwise P-T path involving near-isobaric cooling, suggesting the metamorphism of the Yishui Complex was most likely related to the intrusion and underplating of mantlederived magmas, which may occur in magmatic arc regions, hot spots, or rift environments. Combined with previous data, it is concluded that the Neoarchean is an important crust growth period in the Yishui Complex, and the Late Archean widespread tectonothermal event is possibly related to a mantle plume activity. Mineral abbreviations are after Kretz (1983).

Research paper thumbnail of Zircon U–Pb geochronology and Hf isotopes of major lithologies from the Jiaodong Terrane: Implications for the crustal evolution of the Eastern Block of the North China Craton

The Jiaodong Terrane of the Eastern Shandong Complex in the Eastern Block of the North China Crat... more The Jiaodong Terrane of the Eastern Shandong Complex in the Eastern Block of the North China Craton (NCC) consists predominantly of Archean granitoid gneisses with minor supracrustal rock enclaves or lenses. This study presents new zircon LA-ICP-MS U–Pb and Lu–Hf isotopic data for these lithologies, which help to better understand the Archean crustal evolution of the Eastern Block of the NCC. Magmatic zircon U–Pb data reveal that zircons in the supracrustal rocks and granitoid gneisses were generated by multi-stage events at ~ 2.9 Ga, ~ 2.7 Ga and ~ 2.5 Ga. Metamorphic zircon U–Pb data obtained for these rocks show distinct metamorphic ages at ~ 2.50 and ~ 1.9–1.8 Ga, suggesting that the Jiaodong Terrane experienced a regional metamorphic event at the end of the Neoarchean and encountered reworking by a tectonothermal event that was associated with the formation of the Paleoproterozoic Jiao–Liao–Ji Belt. Magmatic zircons have variable εHf(t) values from − 5.5 to + 7.7 with model ages of 3.92–2.57 Ga, of which most εHf(t) values are positive with a predominant peak of model ages at 3.4–3.1 Ga and a subordinate peak at 2.8–2.7 Ga. These Hf features reveal major juvenile crustal growth stages with significant additions of older crustal materials at 3.4–3.1 Ga and 2.8–2.7 Ga, and a crustal reworking event with minor juvenile additions at ~ 2.5 Ga in the Jiaodong Terrane.

Research paper thumbnail of Zircon U–Pb geochronology and Hf isotopes of major lithologies from the Jiaodong Terrane: Implications for the crustal evolution of the Eastern Block of the North China Craton

Research paper thumbnail of Tectonic affinity and reworking of the Archaean Jiaodong Terrane in the Eastern Block of the North China Craton: evidence from LA-ICP-MS U–Pb zircon ages

Research paper thumbnail of Zircon U-Pb geochronology and Hf isotopes of major lithologies from the Yishui Terrane: Implications for the crustal evolution of the Eastern Block, North China Craton

Research paper thumbnail of Petrology and PT path of the Yishui mafic granulites: implications for tectonothermal evolution of the Western Shandong Complex in the Eastern Block of the North China Craton

Mafic granulites from the Yishui Group of the Western Shandong Complex in the Eastern Block of th... more Mafic granulites from the Yishui Group of the Western Shandong Complex in the Eastern Block of the North China Craton occur as enclaves or boudins within Late Archean TTG gneisses, and are composed mainly of garnet, clinopyroxene, orthopyroxene, plagioclase, hornblende, and minor quartz, ilmenite, and magnetite. Petrographic examination has revealed three distinct metamorphic mineral assemblages: the pre-peak prograde assemblage (M1) of hornblende + plagioclase + quartz + ilmenite + magnetite occurring as inclusions within garnet and pyroxene grains, peak assemblage (M2) of orthopyroxene + clinopyroxene + plagioclase + garnet + hornblende + quartz + ilmenite + magnetite, and post-peak assemblage (M3) represented by garnet + quartz and garnet + ilmenite/magnetite symplectites. Pseudosection modeling using THERMOCALC in the NCFMASHTO model system for a representative sample constrains the P-T conditions of M1, M2 and M3 stages at 660-730 • C/<6.6 kbar, 800-820 • C/8.0-8.5 kbar and 686-710 • C/7.6-8.6 kbar, respectively. The results of petrology and quantitative P-T pseudosection modeling define an anticlockwise P-T path involving near-isobaric cooling following the peak medium-pressure granulite-facies metamorphism, suggesting that the metamorphism of the Yishui Group was most likely related to the intrusion and underplating of mantle-derived magmas. Although the underplating of voluminous mantle-derived magmas leading to granulite-facies metamorphism with an anticlockwise P-T path involving isobaric cooling may occur in continental magmatic arc regions, above hot spots driven by mantle plumes, or in continental rift environments, a mantle plume model is favored because this model can reasonably interpret many other geological features of Late Archean basement rocks from the Western Shandong Complex in the Eastern Block of the North China Craton as well as their anticlockwise P-T paths involving isobaric cooling. The relatively cooler mantle-plume head heated the crust initially, causing amphibolite-facies metamorphism (M1). Subsequently, the relatively hotter mantle-plume tail heated the crust, causing granulite-facies metamorphism (M2). Finally, a near-isobaric cooling process (M3) occurred when the mantle plume ceased to heat the crust. (M. Wu). , whereas anticlockwise P-T paths, especially for those involving isobaric cooling (IBC), reflect metamorphism related to the intrusion and underplating of mantle-derived magmas, which may occur in intra-continental magmatic arc regions , hot spots related to mantle plumes and incipient rift environments . Thus, combined with lithological, structural, geochemical and geochronological data, metamorphic P-T paths can be used to recognize terranes and their tectonic boundaries -subduction zones or collisional belts. Mafic granulites are of particular importance in this regard as they often preserve mineral assemblages suitable for estimating the P-T conditions of metamorphism and textural evidence used to infer metamorphic reaction relations, which are particularly useful in determining metamorphic P-T paths. 0301-9268/$ -see front matter

Research paper thumbnail of Metamorphic PT path and implications of high-pressure pelitic granulites from the Jiaobei massif in the Jiao-Liao-Ji Belt, North China Craton

High-pressure pelitic granulites have recently been found from the Jiaobei massif in the southern... more High-pressure pelitic granulites have recently been found from the Jiaobei massif in the southern segment of the Jiao-Liao-Ji Belt (JLJB), which separates the Eastern Block of the North China Craton into the Longgang and Langrim Blocks. Petrological evidence from these high-pressure pelitic granulites indicates three distinct metamorphic stages (M1-M3). The pre-peak (M1) stage is represented by a mineral assemblage of garnet (core) + inclusion-type minerals within the garnet (biotite + kyanite + muscovite + plagioclase + quartz + ilmenite). The peak (M2) stage is marked by a mineral assemblage of garnet (mantle) + K-feldspar + kyanite + plagioclase + biotite + rutile + ilmenite + quartz. The post-peak (M3) stage is featured by a mineral assemblage of garnet (rim) + sillimanite + plagioclase + biotite + ilmenite + quartz. Using the THERMOCA-LAC technique, the NCKFMASHTO system has been applied to construct pseudosections for a representative high-pressure pelitic granulite sample. P-T conditions for the M1, M2 and M3 stages are constrained at 9.3-10.7 kbar/645-670°C, 14.8-16.2 kbar/860-890°C, and 6.3-8.5 kbar/710-740°C, respectively. The mineral assemblages and P-T conditions of the high-pressure pelitic granulites define a clockwise P-T path involving decompression and cooling following the peak high-pressure granulite facies metamorphism. This suggests that the high-pressure pelitic granulites experienced the initial crustal thickening (M1 and M2), followed by exhumation and cooling (M3), which implies that the southern segment of the JLJB must have been involved in subduction-or collision-related tectonic processes. Therefore, the JLJB may represent another Paleoproterozoic collisional belt along which the Longgang and Langrim Blocks amalgamated to form the Eastern Block.

Research paper thumbnail of Ages, geochemistry and metamorphism of the neoarchean basement in Shandong province

Research paper thumbnail of A synthesis of geochemistry and Sm–Nd isotopes of Archean granitoid gneisses in the Jiaodong Terrane: Constraints on petrogenesis and tectonic evolution of the Eastern Block, North China Craton

Precambrian Research, 2014

The Jiaodong Terrane is situated in the northeastern part of the Shandong Province in eastern Chi... more The Jiaodong Terrane is situated in the northeastern part of the Shandong Province in eastern China, experiencing multi-stage magmatism during the Mesoarchean (∼2.9 Ga) and Neoarchean (∼2.7 Ga and ∼2.5 Ga). It consists dominantly of granitoid gneisses with minor amphibolite enclaves or lenses. This study presents new whole-rock geochemical and Sm-Nd isotopic data for the Archean granitoid gneisses from the Jiaodong Terrane in order to constrain their petrogenesis and tectonic setting. Geochemical studies and petrological features suggest that the protoliths of most granitoid gneisses are typical Archean tonalitic-trondhjemitic-granodioritic (TTG) suites, which are high in SiO 2 (60.9-76.8 wt.%), Al 2 O 3 (12.6-16.8 wt.%), Na 2 O (3.3-5.3 wt.%), Sr (135-604 ppm) and Sr/Y ratios (13.9-84), but low in MgO (0.4-4.5 wt.%), K 2 O (0.7-3.4 wt.%), TiO 2 (0.2-0.9 wt.%), Cr (<0.5-37.9 ppm), Ni (<0.5-24 ppm), Y (2.8-19 ppm) and Mg number (Mg # = 30-45). They are generally enriched in light rare earth elements (LREE) and large ion lithophile elements (LILE), depleted in heavy rare earth elements (HREE) and high field strength elements (HFSE), with slight Eu anomalies. These geochemical features suggest that they were derived from partial melting of metabasaltic rocks leaving eclogite or garnet-amphibolite dominant in the residue. Whole-rock Nd isotopes reveal that the protoliths of Mesoarchean (∼2.9 Ga) granitoid gneisses were derived mainly from juvenile sources, whereas the early Neoarchean (∼2.7 Ga) granitoid gneisses were derived from juvenile sources with significant additions of crustal material and the late Neoarchean (∼2.5 Ga) granitoid gneisses were mainly derived from continental crustal sources. Combined with other geological considerations, a mantle plume model is favored to account for the generation of both early and late Neoarchean granitoid gneisses, whereas the tectonic setting for the Mesoarchean granitoid gneisses remains uncertain due to lack of geological data.

Research paper thumbnail of ZIRCON AGES, HF ISOTOPES AND PT PATH OF THE YISHUI COMPLEX: IMPLICATIONS FOR THE CRUST GROWTH AND TECTONOTHERMAL EVOLUTION OF THE EASTERN BLOCK OF THE NORTH CHINA CRATON

High-grade metamorphic supracrustal rocks and granitoids (TTG suites and charnockites) comprise t... more High-grade metamorphic supracrustal rocks and granitoids (TTG suites and charnockites) comprise the Yishui Complex, one of the major Neoarchean complexes in the Eastern Block of the North China Craton. New zircon dating results reveal the magmatic precursors of the supracrustal metapelites and TTG gneisses were generated at 2.58-2.53 Ga and 2.53-2.52 Ga, respectively, and the charnockites were emplaced around 2.58-2.53 Ga. The metamorphic single zircons and overgrowth rims document consistent metamorphic ages at ~2.50 Ga, suggesting the Yishui Complex experienced a regional metamorphism at the end of Neoarchean. Inherited detrital zircons yield ages between 3.0-2.6 Ga with a peak at 2.7-2.6 Ga, indicating the existence of Early Neoarchean magmatism in the Yishui area. Hf isotopic compositions show the Late Neoarchean zircons have positive εHf(t) values from +1.6 to +7.1, with depleted mantle model ages of 2.78-2.59 Ga, close to their crystallization ages. This suggests a significant crustal growth event at 2.8-2.6 Ga and the Neoarchean crust was predominantly derived from juvenile crustal sources with weak contributions of older crustal materials. A metamorphic study on mafic granulite enclaves has reveled three distinct mineral assemblages: the pre-peak assemblage (M1) of Hb + Pl + Qtz + Ilm + Mt occurring as inclusions within garnet and pyroxene, peak assemblage (M2) of Opx + Cpx + Pl + Grt + Hb + Qtz + Ilm + Mt, and post-peak assemblage (M3) represented by Grt + Qtz symplectites. Pseudosection modeling by THERMOCALC in the NCFMASHTO system for a representative mafic granulite constrains the P-T conditions of M1, M2 and M3 stages at 660-730°C/<6.6 kbar, 800-820°C/8.0-8.5 kbar and 686-710°C/7.6-8.6 kbar, respectively. The petrology and quantitative P-T pseudosection modeling define an anticlockwise P-T path involving near-isobaric cooling, suggesting the metamorphism of the Yishui Complex was most likely related to the intrusion and underplating of mantlederived magmas, which may occur in magmatic arc regions, hot spots, or rift environments. Combined with previous data, it is concluded that the Neoarchean is an important crust growth period in the Yishui Complex, and the Late Archean widespread tectonothermal event is possibly related to a mantle plume activity. Mineral abbreviations are after Kretz (1983).

Research paper thumbnail of Zircon U–Pb geochronology and Hf isotopes of major lithologies from the Jiaodong Terrane: Implications for the crustal evolution of the Eastern Block of the North China Craton

The Jiaodong Terrane of the Eastern Shandong Complex in the Eastern Block of the North China Crat... more The Jiaodong Terrane of the Eastern Shandong Complex in the Eastern Block of the North China Craton (NCC) consists predominantly of Archean granitoid gneisses with minor supracrustal rock enclaves or lenses. This study presents new zircon LA-ICP-MS U–Pb and Lu–Hf isotopic data for these lithologies, which help to better understand the Archean crustal evolution of the Eastern Block of the NCC. Magmatic zircon U–Pb data reveal that zircons in the supracrustal rocks and granitoid gneisses were generated by multi-stage events at ~ 2.9 Ga, ~ 2.7 Ga and ~ 2.5 Ga. Metamorphic zircon U–Pb data obtained for these rocks show distinct metamorphic ages at ~ 2.50 and ~ 1.9–1.8 Ga, suggesting that the Jiaodong Terrane experienced a regional metamorphic event at the end of the Neoarchean and encountered reworking by a tectonothermal event that was associated with the formation of the Paleoproterozoic Jiao–Liao–Ji Belt. Magmatic zircons have variable εHf(t) values from − 5.5 to + 7.7 with model ages of 3.92–2.57 Ga, of which most εHf(t) values are positive with a predominant peak of model ages at 3.4–3.1 Ga and a subordinate peak at 2.8–2.7 Ga. These Hf features reveal major juvenile crustal growth stages with significant additions of older crustal materials at 3.4–3.1 Ga and 2.8–2.7 Ga, and a crustal reworking event with minor juvenile additions at ~ 2.5 Ga in the Jiaodong Terrane.

Research paper thumbnail of Zircon U–Pb geochronology and Hf isotopes of major lithologies from the Jiaodong Terrane: Implications for the crustal evolution of the Eastern Block of the North China Craton

Research paper thumbnail of Tectonic affinity and reworking of the Archaean Jiaodong Terrane in the Eastern Block of the North China Craton: evidence from LA-ICP-MS U–Pb zircon ages

Research paper thumbnail of Zircon U-Pb geochronology and Hf isotopes of major lithologies from the Yishui Terrane: Implications for the crustal evolution of the Eastern Block, North China Craton

Research paper thumbnail of Petrology and PT path of the Yishui mafic granulites: implications for tectonothermal evolution of the Western Shandong Complex in the Eastern Block of the North China Craton

Mafic granulites from the Yishui Group of the Western Shandong Complex in the Eastern Block of th... more Mafic granulites from the Yishui Group of the Western Shandong Complex in the Eastern Block of the North China Craton occur as enclaves or boudins within Late Archean TTG gneisses, and are composed mainly of garnet, clinopyroxene, orthopyroxene, plagioclase, hornblende, and minor quartz, ilmenite, and magnetite. Petrographic examination has revealed three distinct metamorphic mineral assemblages: the pre-peak prograde assemblage (M1) of hornblende + plagioclase + quartz + ilmenite + magnetite occurring as inclusions within garnet and pyroxene grains, peak assemblage (M2) of orthopyroxene + clinopyroxene + plagioclase + garnet + hornblende + quartz + ilmenite + magnetite, and post-peak assemblage (M3) represented by garnet + quartz and garnet + ilmenite/magnetite symplectites. Pseudosection modeling using THERMOCALC in the NCFMASHTO model system for a representative sample constrains the P-T conditions of M1, M2 and M3 stages at 660-730 • C/<6.6 kbar, 800-820 • C/8.0-8.5 kbar and 686-710 • C/7.6-8.6 kbar, respectively. The results of petrology and quantitative P-T pseudosection modeling define an anticlockwise P-T path involving near-isobaric cooling following the peak medium-pressure granulite-facies metamorphism, suggesting that the metamorphism of the Yishui Group was most likely related to the intrusion and underplating of mantle-derived magmas. Although the underplating of voluminous mantle-derived magmas leading to granulite-facies metamorphism with an anticlockwise P-T path involving isobaric cooling may occur in continental magmatic arc regions, above hot spots driven by mantle plumes, or in continental rift environments, a mantle plume model is favored because this model can reasonably interpret many other geological features of Late Archean basement rocks from the Western Shandong Complex in the Eastern Block of the North China Craton as well as their anticlockwise P-T paths involving isobaric cooling. The relatively cooler mantle-plume head heated the crust initially, causing amphibolite-facies metamorphism (M1). Subsequently, the relatively hotter mantle-plume tail heated the crust, causing granulite-facies metamorphism (M2). Finally, a near-isobaric cooling process (M3) occurred when the mantle plume ceased to heat the crust. (M. Wu). , whereas anticlockwise P-T paths, especially for those involving isobaric cooling (IBC), reflect metamorphism related to the intrusion and underplating of mantle-derived magmas, which may occur in intra-continental magmatic arc regions , hot spots related to mantle plumes and incipient rift environments . Thus, combined with lithological, structural, geochemical and geochronological data, metamorphic P-T paths can be used to recognize terranes and their tectonic boundaries -subduction zones or collisional belts. Mafic granulites are of particular importance in this regard as they often preserve mineral assemblages suitable for estimating the P-T conditions of metamorphism and textural evidence used to infer metamorphic reaction relations, which are particularly useful in determining metamorphic P-T paths. 0301-9268/$ -see front matter

Research paper thumbnail of Metamorphic PT path and implications of high-pressure pelitic granulites from the Jiaobei massif in the Jiao-Liao-Ji Belt, North China Craton

High-pressure pelitic granulites have recently been found from the Jiaobei massif in the southern... more High-pressure pelitic granulites have recently been found from the Jiaobei massif in the southern segment of the Jiao-Liao-Ji Belt (JLJB), which separates the Eastern Block of the North China Craton into the Longgang and Langrim Blocks. Petrological evidence from these high-pressure pelitic granulites indicates three distinct metamorphic stages (M1-M3). The pre-peak (M1) stage is represented by a mineral assemblage of garnet (core) + inclusion-type minerals within the garnet (biotite + kyanite + muscovite + plagioclase + quartz + ilmenite). The peak (M2) stage is marked by a mineral assemblage of garnet (mantle) + K-feldspar + kyanite + plagioclase + biotite + rutile + ilmenite + quartz. The post-peak (M3) stage is featured by a mineral assemblage of garnet (rim) + sillimanite + plagioclase + biotite + ilmenite + quartz. Using the THERMOCA-LAC technique, the NCKFMASHTO system has been applied to construct pseudosections for a representative high-pressure pelitic granulite sample. P-T conditions for the M1, M2 and M3 stages are constrained at 9.3-10.7 kbar/645-670°C, 14.8-16.2 kbar/860-890°C, and 6.3-8.5 kbar/710-740°C, respectively. The mineral assemblages and P-T conditions of the high-pressure pelitic granulites define a clockwise P-T path involving decompression and cooling following the peak high-pressure granulite facies metamorphism. This suggests that the high-pressure pelitic granulites experienced the initial crustal thickening (M1 and M2), followed by exhumation and cooling (M3), which implies that the southern segment of the JLJB must have been involved in subduction-or collision-related tectonic processes. Therefore, the JLJB may represent another Paleoproterozoic collisional belt along which the Longgang and Langrim Blocks amalgamated to form the Eastern Block.