Microdiamonds in Alkalic Dolerites from the North China Craton: FTIR and C Isotopic Characteristics

Most of the diamond deposits in China are in the North China Craton. In addition to gem diamonds in kimberlite, a large number of microdiamonds have also been discovered in alkaline dolerites. These microdiamonds show very different characteristics from those recovered in kimberlite. Here, we report the morphology, colour, nitrogen contents, and carbon isotopic compositions of the diamonds recovered from the alkalic dolerites in eastern China. The microdiamonds are mainly cube and rhombic dodecahedron with diameters of 0.2 to 0.6 mm. Infrared spectrum analysis shows that these microdiamonds are mostly type Ib with a small amount of type Ia. The Y centre is obvious in type Ib diamond. Modelling mantle residence times for the IaAB diamonds is about 550 Ma. Nitrogen contents of the diamonds range from 4.5–503 ppm, with a median value of 173 ppm. The total δ13C range of the microdiamonds varies between −18.6 and −21.1‰ and are similar to those of ophiolite diamond.

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Separating multiple episodes of partial melting in polyorogenic crust: An example from the Haiyangsuo complex, northern Sulu belt, eastern China

Geological Society of America Bulletin ◽

10.1130/b35210.1 ◽

2019 ◽

Vol 132 (5-6) ◽

pp. 1235-1256

Author(s):

Peng Feng ◽

Lu Wang ◽

Michael Brown ◽

Songjie Wang ◽

Xiawen Li

Keyword(s):

Partial Melting ◽

North China Craton ◽

North China ◽

Eastern China ◽

Magma Ascent ◽

Magmatic Zircon ◽

Weighted Mean ◽

Heavy Rare Earth Element ◽

Orogenic Collapse ◽

The North

Abstract The exotic Haiyangsuo complex is structurally part of the Sulu belt but its contact relationship with surrounding Sulu gneisses is unexposed and therefore unknown, making its affinity uncertain. It comprises gneisses with in-source leucosomes that host minor metabasite bodies; both are cut by leucogranite dikes. In this study, we determine the timing and petrogenesis of leucosomes and leucogranites and assess the tectonic affinity of the complex based on data from gneisses and metabasites. Most zircon from gneisses and leucosomes has oscillatory-zoned cores with CL-bright overgrowth rims, but some has CL-dark cores or mantles between cores and rims. CL-dark and bright zircon yield weighted mean ages of ca. 1817–1812 Ma. CL-dark zircon has flat heavy rare earth element (HREE) patterns and crystallization temperatures of 829–875 °C, suggesting metamorphic growth, whereas rims have steep HREE patterns but a similar range of crystallization temperatures, suggesting growth from anatectic melt; εHf (t = 1813 Ma) of –18.3 to –10.8 indicates a North China Craton source. Magmatic zircon from metabasites yields ages of ca. 825 Ma, similar to those of scattered metabasite occurrences in the North China Craton. Paleoproterozoic zircon cores were scavenged during magma ascent. By contrast, zircon cores from the leucogranites yield concordant dates of 776–701 Ma, consistent with protolith ages in the Sulu belt, whereas overgrowth mantles and rims yield weighted mean ages of ca. 220 Ma and 162 Ma, respectively. Both mantles and rims host multiphase solid inclusions, representing former melt, suggesting anatexis and crystallization of zircon first during initial decompression and then during orogenic collapse of the Sulu belt; whole-rock Nd and Sr isotope compositions implicate the Sulu belt gneisses as the source of these melts. Our interpretation of these data is that the Haiyangsuo complex has an early geologic history similar to the Jiaobei terrane from the southeastern part of the North China Craton and was incorporated into the Sulu belt during Triassic collision of the Yangtze and North China Cratons. The two stages of melting relate to Upper Triassic early exhumation and Upper Jurassic late-stage orogenic collapse, during which the leucogranite magma was derived from a source similar to one elsewhere in the Sulu belt such as the subducted Yangtze Craton and not the North China Craton. This shows that during continental collisions, crust from the upper plate may be dragged into the subduction channel, deformed, and subsequently exhumed in association with partial melting of the crust.

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Early Cretaceous Xiuyan adakitic granitoids in the Liaodong Peninsula, eastern China: petrogenesis and implications for lithospheric thinning of the North China Craton

Canadian Journal of Earth Sciences ◽

10.1139/cjes-2020-0033 ◽

2021 ◽

Vol 58 (1) ◽

pp. 50-66

Author(s):

Yang Dong ◽

Jingdang Liu ◽

Yanfei Zhang ◽

Shiyong Dou ◽

Yanbin Li ◽

...

Keyword(s):

Early Cretaceous ◽

North China Craton ◽

Lower Crust ◽

North China ◽

Eastern China ◽

Lithospheric Thinning ◽

The North ◽

Magma Sources ◽

Liaodong Peninsula ◽

T Values

Mesozoic magmatic rocks are widely distributed in the North China Craton (NCC) and are crucial to understanding the timing, location, and geodynamic mechanisms of lithospheric thinning of the NCC. In this study, we report geochronological, petrogeochemical, and Lu–Hf isotopic data for adakitic granitoids from different parts of Xiuyan pluton in the Liaodong Peninsula, aiming to constrain their magma sources, petrogenesis, and tectonic implications. The adakites are metaluminous to weakly peraluminous and are classified as high-K calc-alkaline I-type granite with Early Cretaceous zircon U–Pb ages of 129–126 Ma. They exhibit adakite-like geochemical characteristics, such as high Sr content and low Yb and Y contents, coupled with high Sr/Y and no pronounced Eu anomalies. They are enriched in Rb, U, and light rare-earth elements and are depleted in Ta, Nb, P, and Ti. The adakites from the eastern part of the pluton have low εHf(t) values (–8.5 to –4.0) with old TDM2 ages (1.57–1.31 Ga), indicating they were derived from the lower crust containing juvenile mantle-derived materials. In contrast, adakites from the northern part of the pluton have lower εHf(t) values (–19.7 to –16.6) with older TDM2 ages (2.21–2.03 Ga), indicating that they were derived mainly from an ancient crust. Our results show that both adakitic magmas were derived from partial melting of delaminated lower crust. Their relatively high MgO and Ni contents and Mg# values indicate that the melts interacted with mantle peridotites. The lower crust delamination beneath the Liaodong Peninsula resulted from paleo-Pacific plate subduction during the Early Cretaceous, which resulted in thinning of Mesozoic crust in the Xiuyan area.

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Late Jurassic, high Ba–Sr Linglong granites in the Jiaodong Peninsula, East China: lower crustal melting products in the eastern North China Craton

Geological Magazine ◽

10.1017/s0016756816001230 ◽

2017 ◽

Vol 155 (5) ◽

pp. 1040-1062 ◽

Cited By ~ 21

Author(s):

LI-QIANG YANG ◽

YILDIRIM DILEK ◽

ZHONG-LIANG WANG ◽

ROBERTO F. WEINBERG ◽

YUE LIU

Keyword(s):

North China Craton ◽

Late Jurassic ◽

North China ◽

Eastern China ◽

Ultrahigh Pressure ◽

Granitic Rocks ◽

Crustal Melting ◽

Heavy Rare Earth Element ◽

The North ◽

Lower Crustal

AbstractThe Jurassic Linglong granites, intrusive into the North China Craton (NCC) in eastern China, provide a critical record of the first major episode of lithospheric-scale extension and magmatism in NE China during Mesozoic time. Our U–Pb zircon dating reveals that the Linglong granites were emplaced during 161–158 Ma, shortly after the inception of a shallow subduction of the Palaeo-Pacific plate beneath East Asia during Middle Jurassic time. These granites have high alkali contents (K2O + Na2O = 8–9 wt%), low MgO and Mg no. values and variable Cr–Ni abundances. Their relatively high Ba and Sr concentrations, relatively low heavy rare Earth element (HREE) and strongly fractionated REE patterns characterize them as high Ba–Sr granites. The negative whole-rock εNd(t) values ranging from −22.4 to −10.9 and wide-ranging zircon εHf(t) values of −39.1 to −1.5 suggest that magmas of the Linglong granites were produced by partial melting of a garnet-amphibolite-bearing lower crust of the Jiaobei Terrane and by re-melting of the Triassic ultrahigh-pressure (UHP) metamorphic rocks and alkaline suites of the Sulu Terrane. The occurrence in the granitic rocks of inherited zircons of the Neoarchaean, Palaeoproterozoic, Neoproterozoic, Palaeozoic and Triassic ages suggests that magmas of the Linglong granites interacted with the ancient crust in these terranes during their ascent. Asthenospheric upwelling, induced by the steepening and rapid rollback of the Palaeo-Pacific slab during Late Jurassic time, provided the heat source for the inferred lower crustal melting. Trench migration and thermal weakening of the crust caused extensional deformation and thinning in the eastern part of the NCC.

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Mesozoic basins in eastern China and their bearing on the deconstruction of the North China Craton

Journal of Asian Earth Sciences ◽

10.1016/j.jseaes.2011.06.008 ◽

2012 ◽

Vol 47 ◽

pp. 64-79 ◽

Cited By ~ 134

Author(s):

Sanzhong Li ◽

Guochun Zhao ◽

Liming Dai ◽

Xin Liu ◽

Lihong Zhou ◽

...

Keyword(s):

North China Craton ◽

North China ◽

Eastern China ◽

The North

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Age and composition of the Rushan intrusive complex in the northern Sulu orogen, eastern China: petrogenesis and lithospheric mantle evolution

Geological Magazine ◽

10.1017/s0016756808005463 ◽

2008 ◽

Vol 146 (2) ◽

pp. 199-215 ◽

Cited By ~ 24

Author(s):

HUA-YUN TANG ◽

JIAN-PING ZHENG ◽

CHUN-MEI YU

Keyword(s):

North China Craton ◽

North China ◽

Eastern China ◽

Major Elements ◽

Intrusive Complex ◽

Mantle Evolution ◽

The North ◽

High K ◽

Cratonic Mantle ◽

Light Rare Earth Elements

AbstractZircon U–Pb age, whole-rock elemental and Sr–Nd isotopic data are presented for the Rushan intrusive complex from the northern Sulu orogen, China. The intrusion, emplaced at c. 111 Ma, consists mainly of biotite-bearing gabbro and pyroxene-bearing diorite. The rocks are high-K calc-alkaline in major elements, and enriched in large ion lithophile elements (LILE) and light rare earth elements (LREE), depleted in high field strength elements (HFSE), and possess narrow ranges of initial 87Sr/86Sr (0.70746–0.70827) and ɛNd(t) (−12.37 to −8.26). The complex is interpreted to originate from decompression melting of spinel-facies cratonic mantle that was metasomatized by the subducted Yangtze crustal materials and the melts experienced fractionation of olivine, clinopyroxene, apatite and Fe–Ti oxides. The Rushan complex is similar in composition to other Early Cretaceous mafic-intermediate complexes from the southern margin of the North China Craton, such as the Fangcheng basalts and Yinan gabbros, implying the mantle source of the Rushan intrusion is tectonically affiliated to the southern wedge of the Craton. We infer that the Rushan complex formed in an extensional regime corresponding to the asthenosphere upwelling during gradual erosion and replacement of the cratonic mantle by the fertile lithosphere beneath the eastern North China Craton.

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