Figure
1.
The location of the sheeted dike complex in the Huangling anticline, northern Yangtze craton (modified from Peng et al., 2012).
| Citation: | Hao Deng, Timothy M Kusky, Lu Wang, Songbai Peng, Xingfu Jiang, Junpeng Wang, Songjie Wang. Discovery of a Sheeted Dike Complex in the Northern Yangtze Craton and Its Implications for Craton Evolution. Journal of Earth Science, 2012, 23(5): 676-695. doi: 10.1007/s12583-012-0287-9
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Sheeted dikes, which are a product of magma intrusions without intervening host rocks, are usually thought to form in extensional environments such as along mid-oceanic ridges or above subduction zones, in which seafloor spreading can induce faults and fractures along which more and more new magma can flow laterally and vertically to produce dikes presenting a sheeted shape (Dilek and Furnes, 2011; Robinson et al., 2008; Dilek et al., 1998). The existence of sheeted dikes in ophiolites is generally regarded as strong evidence for the origin of ancient oceanic crust now obducted onto continental margins by tectonic movements (Gass, 1990), hence sheeted dikes have long been considered as a key and essential component of oceanic crust and ophiolites forming in extensional magmatic settings. However, the formation of a sheeted dike complex requires very specific conditions, particularly an adequate melt supply and an approximate balance between the rates of spreading and magma supply (Robinson et al., 2008). Such a balance seems to exist at magma-rich mid-ocean ridges, where both the spreading rate and magma supply are probably linked to mantle convection, and thus sheeted dikes are interpreted as a principal part of the oceanic crust. In contrast, large and well-developed sheeted dike complexes are rare in ophiolites, which are typically formed or modified in suprasubduction zone environments, because of disequilibrium between the rates of magma supply and extension, or because of later deformation and metamorphism during ophiolite emplacement. In suprasubduction zone environments spreading is controlled by the rate of slab rollback, whereas the magma supply depends on such factors as the local temperature profile, angle of subduction and the lithology of the subducting crust and mantle wedge (Robinson et al., 2008). Hence, Robinson et al. (2008) suggested that sheeted dikes may be an unnecessary component in suprasubduction-zone (SSZ) ophiolites, because spreading rate and magma supply rarely balance each other in this environment. In fact, sheeted dikes are only present in about 10% of known ophiolite fragments world-wide (Kusky et al., 2011; Robinson et al., 2008) supplying strong evidence for this view. However once sheeted dikes are documented in ophiolites, their presence not only provides evidence for that particular mafic/ultramafic complex being ophiolitic, but can help assess the tectonic setting in which the ophiolite formed. Sheeted dikes may be an unnecessary component in ophiolites, but their presence in some ophiolites is convincing evidence of their sea-floor origin.
In this article we present a detailed study of the sheeted dike complex in the Miaowan ophiolite, which is located on the northern margin of the Yangtze craton (Peng et al., 2012, 2010), in order to document the mode and nature of extensional tectonics and associated magmatism during its formation.
The geological setting of the Huangling anticline, located in the northern margin of the Yangtze craton, has been described in detail by Peng et al. (2012) and is not repeated herein again. The Miaowan Group is a sub-group of the Kongling Group (Peng et al., 2012), which is located in the southern Huangling anticline and the only Archean terrane that crops out in the Yangtze craton (Gao et al., 1999), consists mainly of layered fine-grained amphibolite and quartzite, with intermittently exposed some ultramafic and gabbroic rocks (Peng et al., 2012; Wang et al., 2002; Ma et al., 1997).
Peng et al. (2010) originally described in detail the mafic and ultramafic rocks in Miaowan Group and interpreted them to be a fragment of an ophiolite complex, formed in the Mesoproterozoic and then dismembered by later tectonic movements. Peng et al. (2012) then documented the authenticity of the Miaowan ophiolite in the southern part of the Huangling anticline and described a typical combination of ophiolitic rock units. The Miaowan ophiolite crops out as a structurally complex, fault-bounded, WNW-striking belt in the center of the Huangling anticline (Fig. 1). It forms a large, south-vergent fold-nappe structure, and is cut by numerous internal faults. Peng et al. (2012) recognized a complete Penrose-style ophiolite suite and briefly described the SDC. In this study, we carried out detailed research on a small area of the dikes, mapping at a scale of 1 : 1 000, and constructing a measured profile of the complex (Fig. 2). Herein, we describe the geological and geochemical character of the meta-diabase and meta-gabbro and also re-examine the existing geochemical data of the meta-plagiograinte in the SDC, and then discuss its significance for the ophiolite and the role of the ophiolite in the tectonic evolution of the Yangtze craton.
The Miaowan ophiolite consists of harzburgite tectonite, podiform chromite, dunite, layered and iso-tropic gabbro, a sheeted dike complex, meta-pillow lavas, chert, and tectonically interleaved marble (Peng et al., 2012). The SDC is located near Xiaoxikou Village of Yichang City, Hubei Province (Fig. 1). The best-preserved section of the SDC is a 450-m-long section, located north of Xiaoxikou Village. The complex consists of nearly 100% dikes, which have a general strike of about 120°-160° and dip to the northeast at an angle of about 70°-85°.
The SDC mainly consists of meta-diabase, meta-plagiogranite to monzogranite, and small amounts of meta-gabbro and ultramafic rocks, which exhibit mutually cross-cutting relationships (Figs. 2, 3a and 3c). The thickness of individual dikes ranges from a dozen centimeters to several meters, but most are in the range of 30-50 cm. Because of the strong deformation and metamorphic recrystallization in the area, the chill margins on most dikes are difficult to determine. However, some of the dikes, preserving one-way chilled margins (Figs. 2, 3b, 3d, 3f and 4), suggest that they intruded into the center of previously formed dikes (Kusky et al., 2011). More common are dikes with two-way chilling (Figs. 2 and 3e), but the majority of the dikes have indistinct chilled margins because of the later strong deformation. The one-way chilled margins are mostly distributed along the southwestern side of individual dikes and strike NNW, suggesting that the spreading axis lay to the SW. The lower part of the SDC (Fig. 2) contains some gabbro intruding the plagiogranite, possibly representing the transition between dikes and gabbros (Fig. 3f). In the upper part of the SDC meta-diabase dikes are intruded by plagiogranite dikes and some of meta-diabase dikes intrude the plagiogranite, showing that they are coeval (Fig. 3c). Strongly deformed amphibolite with 50 cmto 1 m-wide, almond-shaped bodies in the top of the DC are interpreted as meta-pillow lavas (Figs. 2 and 3g) (Peng et al., 2012). The gradation from dikes to pillows takes place over 20-50-m-thick transition zone, grading first through several tens of meters of mixed dikes and pillows, then into a severalhundred-m-thick section of strongly flattened pillows that preserve epidosite-rich cores (Peng et al., 2012; Wang et al., 2012). All dikes underwent strong ductile and brittle deformation and amphibolite-facies metamorphism (Fig. 3h).
The Xiaoxikou SDC mainly consists of meta-diabase, meta-plagiogranite to monzogranite, meta-gabbro and ultramafic rocks. However, these rocks have been strongly modified by ductile and brittle deformation, sub-sea floor metamorphism and regional metamorphism. As the result of these processes, most primary minerals have been replaced.
Meta-diabase dikes comprise most of the SDC and consist of dark grayish-green, massive rocks with a meta-diabasic texture. The diabase is strongly deformed and metamorphosed into amphibolite so that the diabasic texture is only rarely preserved (Fig. 5a). The major minerals include hornblende (45%-50%), plagioclase (40%-45%), magnetite (3%-5%), biotite (0.5%-1%), apatite (0.5%-1%) and minor rutile and epidote. The plagioclase, whose size is generally 0.2-0.25 mm, is mostly present as irregular granular or, less commonly, as lath-shaped crystals. Hornblende, whose size is about 0.2-0.25 mm and pleochroism is from dark green to light yellow-green, is mostly present as irregular granular to columnar grains with hexagonal cross-sections and hornblendetype cleavage. Locally, the amphibole presents a weak preferred orientation (Fig. 5b).
Meta-diabase dikes are intruded by metaplagiogranitic to monzogranitic dikes and some of the meta-diabase dikes also intrude the meta-plagiogranite, showing that the plagiogranite is the same age as the sheeted dike complex. Therefore we suggest that the meta-plagiogranite is another important component of the SDC, and also underwent metamorphism and deformation. The rocks are light gray to white and massive with a meta-granitic texture. Some samples have a relic blastoporphyritic texture in thin section (Fig. 6c). The major minerals include plagioclase (55%-60%), quartz (20%-30%), hornblende (5%-10%), biotite (1%-2%), magnetite (1.5%-3%), apatite (0.5%-1%) and minor orthoclase. The plagioclase, which is generally less than 0.5 mm across, mostly presents irregular to hypidiomorphic columnar grains, some of which have been elongated by deformation. Some of the plagioclase has visible polysynthetic twinning between crossed polars (Fig. 5c), but most of grains have been saussuritized. Quartz occurs as small (0.1-0.2 mm), irregular grains, whereas hornblende forms narrow columnar or acicular crystals up to 0.5 mm long. Elongate feldspar, hornblende and biotite have a strong orientation and form an obvious schistosity (Figs. 5d and 5e).
Meta-gabbro is only locally present in the SDC (Fig. 2), mostly in the transition zone between the SDC and the underlying gabbro sequence. The gabbro in the SDC, which has been deformed and metamorphosed to the amphibolite facies, is dark gray and massive, with a well-developed meta-gabbroic texture (Fig. 5f). The major minerals include plagioclase (45%-50%), hornblende (45%-50%), magnetite (1%-1.5%), apatite (0.5%-1%) and a small amount of pyrite. The plagioclase occurs as small, irregular grains, about 0.15 mm across, that have mostly been replaced by chlorite. Hornblende in the meta-gabbro forms irregular, granular to columnar crystals up to 0.15 mm long that are strongly oriented (Fig. 5f).
Ultramafic rocks occur both as rare dikes and as screens in the SDC, and all of them have been highly deformed and metamorphosed. They are grayish-green in color and massive with subhedral, columnar granular blastic textures (Figs. 5g and 5h). The main minerals include hornblende (60%-65%), chlorite (30%-35%), magnetite (0.5%-1%), feldspar (2%-3%) and a small amount of biotite, apatite and sphene. Most of the hornblende occurs as irregular granular to hypidiomorphic columnar grains less than 0.1 mm across. The chlorite forms very small greenish flakes with well-developed cleavage and nearly parallel extinction. The chlorite is Mg-rich penninite. Both the hornblende and chlorite are strongly oriented, producing an obvious schistosity (Figs. 5g and 5h).
The samples from the SDC collected for major and trace element analysis were taken from Xiaoxikou Village on the southern Huangling anticline. The major element analyses were performed in the Comprehensive Rock and Mineral Test Center, China University of Geosciences, Wuhan, and trace element analyses were completed in the LA-ICP-MS lab at the State Key Laboratory of China University of Geosciences, Wuhan. The analytical precision is estimated to be better than 1%-3%. The major and trace element analyses are presented in Table 1, and were interpreted with the aid of the geochemical software tool package "Geokit program" (Lu, 2004). Because the samples experienced amphibolite facies metamorphism, we mostly use the HFSE (high field strength elements), such as Ti, Zr, Nb, Ta, Hf and Th, REE, and transition metal elements (Sc, V, Cr, Ni), which are relatively immobile during metamorphism and deformation to classify the rock types, determine the genesis of the magmas and to identify the petrotectonic environment of formation (Janney and Castillo, 1996; Rollinson, 1993).
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Meta-diabase is the major component of the SDC, so its composition is used investigate the petrotectonic environment of formation for the SDC. From Table 1, it is obvious that the meta-diabase dikes are mafic rocks with SiO2 contents of 50 wt.%-52 wt.%, and relatively high contents of CaO, Al2O3, MgO, FeO, Fe2O3 (MgO=5.03 wt.%-7.72 wt.%, Mg#=44-56). TiO2 content is medium (TiO2 wt.%=1.31 wt.%-1.70 wt.%). These compositions are similar to those of mid-ocean ridge tholeiite (MORB) (Pearce, 1983).
In the SiO2 vs. Zr/TiO2 chemical classification diagram for volcanic rocks (Fig. 6a) (Winchester and Floyd, 1977), the meta-diabases plot in the field of sub-alkaline basalt. They also plot in the sub-alkaline basalt to basaltic andesite field in the Zr/TiO2 vs. Nb/Y diagram (Fig. 6b) (Winchester and Floyd, 1977), and display low Nb/Y ratios (0.56-0.59).
In both the TFe/MgO vs. TiO2 diagram (Fig. 7c) (Glassley, 1974), and the TiO2-K2O-P2O5 discriminant diagram (Fig. 7d) (Pearce et al., 1975), the samples plot in the MORB field. Thus, we suggest that the meta-diabases represent tholeiitic basalts formed originally at a mid-ocean ridge.
The meta-diabases from the SDC show flat to slightly LREE depleted chondrite-normalized REE patterns with no obvious Eu anomalies (δEu=0.89-1.07), very similar to those of N-MORB (Fig. 7a). The ΣREE is 44.32-48.85 μg/g (average 46.58 μg/g), which is respectively 14.20 times that of chondrite and 0.58 times that of OIB, but close to that of N-MORB (39.1 μg/g). The ΣLREE/ΣHREE is 1.31-1.71 and the average (La/Yb)N ratio is 0.75, indicating little differentiation between LREE and HREE, demonstrating that their REE distribution characteristics are similar to N-MORB.
In the MORB-normalized trace element spider diagram (Fig. 7b) (Pearce, 1982), the SDC rocks are clearly enriched in large ion lithophile elements (LILE) (Sr to Ba). Because all of these elements (except Th) are mobile during alteration and metamorphism, they are less useful for determining the environment of formation than the non-mobile HFSE and REE. The latter have patterns very similar to those of typical MORB. This indicates that they likely come from N-MORB or mantle source basalts similar to N-MORB, and have not been contaminated by conti-nental crustal material.
Peng et al. (2012) previously listed three geochemical data for the palgiogranites in the SDC, but didn't make a detail analysis. In this contribution, we will re-investigate and analyze these geochemical characteristics in detail.
Minor granitoids found in ophiolitic complexes have compositions ranging from alkali granite through trondhjemite and tonalite to diorite and are collectively referred to as oceanic plagiogranites (Coleman and Peterman, 1975). Koepke et al.(2007, 2004) suggested that the oceanic plagiogranites are commonly present in the oceanic crust, in particular at the base of the sheeted dike complex. Oceanic plagiogranites have been found in many ophiolites, such as the Troodos ophiolite in Cyprus, Oman ophiolite, Fournier ophiolite in Canada, and ophiolites from the Northeast Jiangxi Province in China (Rollinson, 2009; Li and Li, 2003a; Amri et al., 1996; Flagler and Spray, 1991; Coleman and Donato, 1979). These oceanic plagiogranites are believed to represent products of either differentiated MORB, or liquid immiscibility resulting in the occurrence of a mafic and of a felsic melt, or hydrous partial melting of gabbros or sheeted dikes (France et al., 2010). Li and Li (2003b) summarized the geochemical characteristics, tectonic setting and geological implications of the oceanic plagiogranites and subdivided them into four types: fractionation-type, shearing-type, subduction-type, and obduction-type. Thus, oceanic plagiogranites are typically pre-sent in ophiolites and are very useful and significant for demonstrating the tectonic setting and even dating of ophiolites.
The plagiogranites in the SDC have SiO2 of about 60 wt.%-73 wt.%, high Na2O (average=7%) and very low K2O (average 0.13 wt.%) (Table 1). These are meta-aluminous rocks with an average A/CNK (molecular Al2O3/(CaO+Na2O+K2O)) of 1.06 wt.%. On the An-Ab-Or normative rock classification diagram (O'Connor, 1965), two of the analysed meta-plagiogranites from the SDC plot in the granodiorite field and one plots in the tonalite field (Fig. 8).
The meta-plagiogranites from the SDC show LREE enriched and slightly HREE depleted chondrite-normalized REE patterns (Fig. 9a), with significant negative Eu anomalies (δEu=0.68). ΣLREE/ΣHREE=4.11 and (La/Yb)N=3.26 showing obvious differentiation between LREE and HREE. In the MORB-normalized trace element diagram (Fig. 9b), they are slightly enriched in LILE and depleted in HFSE, classic characteristics of subduction environments. They show positive Th and Pb anomalies, and negative anomalies for Ta, Nb, Sr, P and Ti. Based on these trace characteristics, these plagiogranites may have formed in a subduction zone environment. It is clear that fractional crystallization has taken place during the formation of these plagiogranites, as indicated by the striking depletions in Ta, Nb, Sr, P, Ti and Eu (Fig. 9b). Negative Nb-Ti anomalies are considered to be related to fractionation of Ti-bearing phases (ilmenite, titanite, etc.) and negative P anomalies commonly reflect apatite separation. Strong Eu depletion requires extensive fractionation of plagioclase, which would also result in negative Sr-Eu anomalies. Thus, the composition of the meta-plagiogranites, suggest formation by strong fractional crystallization of a mafic magma.
In the Pearce et al. (1984) Rb-(Yb+Ta) discriminant diagram (Fig. 10a), the samples fall into the boundary area between volcanic arc granites. In the Pearce et al. (1984) Y-Nb discriminant diagram (Fig. 10b), the samples also fall into the volcanic arc granite and syn-collisonal granite.
In conclusion, the meta-plagiogranites are not the partial melting product of the mafic rocks and presumably formed by strong fractional crystallization of a mafic magma. The geochemical evidence suggests that the plagiogranites formed in a suprasubduction environment, consistent with the findings of Peng et al. (2012).
Locally, in the lower part of the SDC, gabbro in-trudes plagiogranite, shown by chilled margins on the gabbro (Fig. 3f). In the upper part of the SDC, the meta-diabase dikes and plagiogranite dikes are mutually intrusive, indicating an overlap in age. To help understand these age relationships, we collected meta-plagiogranites and meta-gabbros from the SDC for U-Pb geochronology, based on their potential to yield the age of the SDC.
LA-ICP-MS U-Pb and trace element data were obtained for zircon from four samples from the SDC. Data from these analyses is shown in Table 2 (supplementary data). Zircon grains were collected from approximately 20 kg rock for each sample using standard heavy liquid techniques. Zircon crystals with good crystallization and transparency were selected from the heavy fraction using a binocular microscope. Polished zircon grains were imaged by cathodoluminescence (CL) on a JEOL JXA-8100 electron microprobe and a LEO1450VP scanning electronic microscope at the Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing. The U-Pb and trace element analyses of zircons were carried out using a LA-ICP-MS at the State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan. The operating conditions for the laser ablation system and the ICP-MS instrument, and the data reduction procedures are the same as those described in Liu Y S et al.(2010a, b, 2008) and Liu X M et al. (2008). Concordia diagrams and weighted mean calculations were made using Isoplot/Ex_ver3 (Ludwig, 2003).
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Four representative and fresh samples, two of which are meta-plagiogranites with another two being meta-gabbros, were selected from the SDC for age dating.
Sample MW24-1 is from a meta-plagiogranite dike that intruded meta-diabase dikes and was mutually intruded by the diabase dikes (Figs. 2 and 3c). The zircon grains have a uniform yellowish-brown color, are mostly euhedral to subhedral and about 20×60 μm in size. Their aspect ratios are between 1.0 and 1.5. Most of the zircons show weak or cloudy zoning in their CL images, indicating typical recrystallization of originally magmatic grains (Figs. 11a–11d). The Th/U ratios from the 7 measurement points are between 0.31 and 1.09, indicating a magmatic origin with some recrystallization. Most measurements fall on, or slightly below, the concordia curve (Fig. 13a), yielding an age of 1 026±79 Ma (MSWD=2.4). One grain yields a xenocrystic age of 2 310±210 Ma.
Sample MW25-1 is also from a metaplagiogranite dike cut by a meta-gabbro dike (sample MW25-2) at the base of the SDC (Fig. 3f). Hence, sample 11MW25-1 from the meta-plagiogranite dike can yield the initial formation age of the SDC, and the sample 11MW25-2 from the meta-gabbro dike should show the age of the younger intrusion. The zircons from 11MW25-1 are a uniform yellowish-brown color and the grains are elongated, prismatic and mostly euhedral to subhedral. The grains are mostly about 60 μm wide and 100–150 μm long, with and aspect ratio between 1.0 and 1.5. Most of the zircons show weak or cloudy zoning in their CL images (Figs. 11e–11h). The Th/U ratios of the 24 data points are between 0.41 and 1.01, typical of magmatic grains with some recrystallization. All 24 measurements plot on or slightly below the concordia curve (Fig. 12b), yielding an age of 1 049±23 Ma (MSWD=1.9).
Zircons from sample MW25-2 of the metagabbro dike are also yellowish-brown, mostly prismatic and euhedral in shape, with aspect ratios of 1 to 1.5. Most are somewhat cloudy in CL images (Figs. 11i–11l). The Th/U ratios from the six measurement points of zircons are between 0.35 and 0.99, indicating a magmatic origin. Six measurements of these zircons yielded an age of 1 042±120 Ma (MSWD=4.5) with most grains falling on or near the concordia (Fig. 12c). Thus, this sample is the same age as MW24-1 within the analytical error (2σ).
Sample MW25-3 was collected at the base of the transition zone between the SDC and the isotropic gabbro. The grain size of MW25-3 is coarser than that of MW25-2. Zircons from this sample are uniformly yellowish-brown in color, range from 60–150 μm in size with aspect ratios between 1.0 and 1.5. Most are also have euhedral, prismatic shapes. A few grains show weak or cloudy zoning in their CL images (Figs. 11m–11p). The Th/U ratios from the 20 measured points are between 0.44 and 1.20, indicate a magmatic origin. Twenty of the measured points yielded an age of 1 096±32 Ma (MSWD=4.3) with most grains falling on or near concordia (Fig. 12d). Peng et al. (2012) reported a somewhat older age of 1 118±24 Ma, for foliated meta-gabbro that may reflect the initial magmatism in the ophiolite. The age of sample MW25-3 is the same as that reported by Peng et al. (2012) within the analytical error.
The mutually intrusive relationships between the meta-plagiogranites, the meta-gabbros and meta-dia-base indicate that they are the same age, as confirmed by our dating results, which show that the ophiolite formed at 1 026-1 049 Ma in the Neoproterozoic.
The Miaowan ophiolite is located along the Dengcun, Taipingxi region in the southern part of Huangling anticline, located on the northern margin of the Yangtze craton (Peng et al., 2012). The SDC is a very important and significant part of the Neoproterozoic Miaowan ophiolitic sequence. It grades downward into gabbro and ultramafic rocks, and upward into meta-pillow lavas. Some of the dikes preserve one-way chilled margins, typical of extensional ophiolitic settings, others preserve two-way chilled margins. However, most of the chilled margins have been obliterated by strong deformation and metamorphism. The one-way chilled margins are mostly located on the southwestern side of individual dikes that strike NNW, suggesting that the spreading axis lay to the SW in the modern coordinates.
The SDC is mainly composed of meta-diabase (dolerite), meta-plagiogranite, and small amounts of meta-gabbro and ultramafic rocks. The geochemical studies of the meta-diabase show that their magma is sub-alkaline type (low potassium tholeiite). The chon-drite-normalized rare earth elements (REE) patterns of the meta-diabase from the SDC show flat type or slightly depleted LREE with no obvious Eu anomalies, (La/Yb)N=0.56-0.94, all of which are similar to N-MORB patterns. Given that the meta-plagiogranites show evidence of formation in a suprasubduction zone environment, we suggest that the basalts were originally island arc tholeiites, perhaps formed in an extensional forearc setting.
Our geochemical studies of the SDC support the previous interpretation that Miaowan ophiolite formed in suprasubduction zone environment (Peng et al., 2012). Based on our dating results, the age of the ophiolite is 1 026-1 049 Ma, slightly older than the age suggested by Peng et al. (2012) (985-1 118 Ma).
The Miaowan ophiolite provides evidence for the presence of a Proterozoic oceanic basin and subduction zone in the northern margin of Yangtze craton. South China has been interpreted as an important part of Rodinia (Li et al., 1995). The discovery may be very significant and helpful for reassessing the relationship between the Yangtze craton and the Rodinia supercontinent.
Through the description of petrology, geochemistry and geochronology of various rocks from the SDC of the Miaowan ophiolite, we conclude the following:
(1) The SDC is mainly composed of me-ta-diabase (dolerite), meta-plagiogranite, and small amounts of meta-gabbro and ultramafic rocks.
(2) The geochemical studies of meta-diabase show that the parental magma was a sub-alkaline, low-K basalt type, probably an arc tholeiite. This interpretation is supported by the suprasubduction zone character of the associated meta-plagiogranites.
(3) From the LA-ICPM U-Pb zircon dating, the age of the ophiolite is considered to lie between 1 026-1 049 Ma.
(4) The recognition of a SDC within the Miaowan ophiolite suggests the former presence of a Proterozoic oceanic basin and subduction zone in the northern margin of Yangtze craton. This discovery may be very significant for reassessing the relationship between Yangtze craton and the Rodinia supercontinent.
This study was supported by the National Natural Science Foundation of China (Nos. 91014002, 40821061, 41272242), Ministry of Education of China (No. B07039), the Open Foundation of Ministry of Education (No. TGRC201024), the Postdoctoral Science Foundation (No. 20100471203) and the Ministry of Land and Resources Foundation (No. 1212010670104). We sincerely thank Prof. Paul Robinson, from the Dalhousie University in Canada, for his suggestions and the reviewers for their helpful comments to improve the quality of the article.
| Amri, I., Benoit, M., Ceuleneer, G., 1996. Tectonic Setting for the Genesis of Oceanic Plagiogranites: Evidence from a Paleospreading Structure in the Oman Ophiolite. Earth and Planetary Science Letters, 139(1–2): 177–194 doi: 10.1016/0012-821x(95)00233-3 |
| Coleman, R. G., Peterman, Z. E., 1975. Oceanic Plagiogranite. Journal of Geophysical Research, 80(8): 1099–1108 doi: 10.1029/JB080i008p01099 |
| Coleman, R. G., Donato, M. M., 1979. Oceanic Plagiogranite Revisited. In: Barker, F., ed., Trondhjemites, Dacites and Related Rocks. Elsevier, Amsterdam. 149–168 |
| Dilek, Y., Moores, E. M., Furnes, H., 1998. Structure of Modern Oceanic Crust and Ophiolites and Implications for Faulting and Magmatism at Oceanic Spreading Centers. In: Buck, R., Karson, J., Delaney, P., et al., eds., Faulting and Magmatism at Mid-Ocean Ridges. American Geophysical Union Monograph, 106: 219–266 |
| Dilek, Y., Furnes, H., 2011. Ophiolite Genesis and Global Tectonics: Geochemical and Tectonic Fingerprinting of Ancient Oceanic Lithosphere. Geological Society of America Bulletin, 123(3–4): 387–411 http://ci.nii.ac.jp/naid/20001226208 |
| Flagler, P. A., Spray, J. G., 1991. Generation of Plagiogranite by Amphibolite Anatexis in Oceanic Shear Zones. Geology, 19(1): 70–73 doi: 10.1130/0091-7613(1991)019<0070:GOPBAA>2.3.CO;2 |
| France, L., Koepke, J., Ildefonse, B., et al., 2010. Hydrous Partial Melting in the Sheeted Dike Complex at Fast Spreading Ridges: Experimental and Natural Observations. Contributions to Mineralogy and Petrology, 160: 683–704 doi: 10.1007/s00410-010-0502-6 |
| Gao, S., Ling, W. L., Qiu, Y. M., et al., 1999. Contrasting Geochemical and Sm-Nd Isotopic Compositions of Archean Metasediments from the Kongling High-Grade Terrain of the Yangtze Craton: Evidence for Cratonic Evolution and Redistribution of REE during Crustal Anatexis. Geochimica et Cosmochimica Acta, 63(13–14): 2071–2088 http://www.sciencedirect.com/science/article/pii/S0016703799001532 |
| Gass, I. G., 1990. Ophiolites and Oceanic Lithosphere. In: Malpas, J., Moores, E. M., Panayiotou, A., et al., eds., Ophiolites, Oceanic Crustal Analogues. Proceedings of the Symposium "Troodos 1987", Nicosia. 1–10 |
| Glassley, W., 1974. Geochemistry and Tectonics of the Grescent Volcanic Rocks, Olympic Peninsula, Washington. Geologic Science of American Bulletin, 85: 785–794 doi: 10.1130/0016-7606(1974)85<785:GATOTC>2.0.CO;2 |
| Janney, P. E., Castillo, P. R., 1996. Basalts from the Central Pacific Basin: Evidence for the Origin of Cretaceous Igneous Complexes in Jurassic Western Pacific. Journal of Geophysical Research, 101: 2875–2893 doi: 10.1029/95JB03119 |
| Koepke, J., Feig, S. T., Snow, J., et al., 2004. Petrogenesis of Oceanic Plagiogranites by Partial Melting of Gabbros: An Experimental Study. Contributions to Mineralogy and Petrology, 146(4): 414–432 doi: 10.1007/s00410-003-0511-9 |
| Koepke, J., Berndt, J., Feig, S. T., et al., 2007. The Formation of SiO2-Rich Melts within the Deep Oceanic Crust by Hydrous Partial Melting of Gabbros. Contributions to Mineralogy and Petrology, 153: 67–84 doi: 10.1007/s00410-006-0135-y |
| Kusky, T. M., Wang, L., Dilek, Y., et al., 2011. Application of the Modern Ophiolite Concept with Special Reference to Precambrian Ophiolites. Science China (Series D), 54: 315–341 doi: 10.1007/s11430-011-4175-4 |
| Li, W. X., Li, X. H., 2003a. Adakite Granites within the NE Jiangxi Ophiolites, South China: Geochemical and Nd Isotopic Evidence. Precambrian Research, 112: 29–44 http://www.sciencedirect.com/science/article/pii/S0301926802002061 |
| Li, W. X., Li, X. H., 2003b. Rock Types and Tectonic Significance of the Granitoids Rocks within Ophiolites. Advance in Earth Sciences, 18: 392–397 (in Chinese with English Abstract) http://www.researchgate.net/publication/313511815_Rock_types_and_tectonic_significance_of_the_granitoids_rocks_within_ophiolites |
| Li, Z. X., Zhang, L., Powell, C. M., 1995. South China in Rodinia: Part of the Missing Link between Australia-East Antarctica and Laurentia? Geology, 23(5): 407–410 doi: 10.1130/0091-7613(1995)023<0407:SCIRPO>2.3.CO;2 |
| Liu, X. M., Gao, S., Diwu, C. R., et al., 2008. Precambrian Growth of Yangtze Craton as Revealed by Detrital Zircon Studies. American Journal of Science, 308(4): 421–468 doi: 10.2475/04.2008.02 |
| Liu, Y. S., Hu, Z. C., Gao, S., et al., 2008. In Situ Analysis of Major and Trace Elements of Anhydrous Minerals by LA-ICP-MS without Applying an Internal Standard. Chemical Geology, 257(1–2): 34–43 http://cms.kdis.edu.cn/cms/geology_cug/achievements/fabiaowenzhang/resource/414f3b8022107c51b3554fd7277929d6.pdf |
| Liu, Y. S., Gao, S., Hu, Z. C., et al., 2010a. Continental and Oceanic Crust Recycling-Induced Melt-Peridotite Interactions in the Trans-North China Orogen: U-Pb Dating, Hf Isotopes and Trace Elements in Zircons of Mantle Xenoliths. Journal of Petrology, 51(1–2): 537–571 |
| Liu, Y. S., Hu, Z. C., Zong, K. Q., et al., 2010b. Reappraisement and Refinement of Zircon U-Pb Isotope and Trace Element Analyses by LA-ICP-MS. Chinese Science Bulletin, 55: 1535–1546 (in Chinese) doi: 10.1007/s11434-010-3052-4 |
| Lu, Y. F., 2004. Geokit: A Geochemical Software Package Constructed by VAB. Geochemistry, 33(5): 459–464 (in Chinese with English Abstract) http://ci.nii.ac.jp/naid/10030173896 |
| Ludwig, K. R., 2003. User's Manual for Isoplot/EX Version 3.00: A Geochronological Toolkit for Microsoft Excel. Berkeley Geochronology Center Special Publication 4, California. 1–70 |
| Ma, D. Q., Li, Z. C., Xiao, Z. F., 1997. The Constitute, Geochronology and Geologic Evolution of the Kongling Complex, Western Hubei. Acta Geoscientica Sinica, 18(3): 233–241 (in Chinese with English Abstract) http://en.cnki.com.cn/Article_en/CJFDTOTAL-DQXB703.000.htm |
| O'Connor, J. T., 1965. A Classification for Quartz-Rich Igneous Rocks Based on Feldspar Ratios. U. S. Geological Survey Professional Paper, Washington. 525B: 79–84 |
| Pearce, T. H., Gorman, B. E., Birkett, T. C., 1975. The TiO2-K2O-P2O5 Diagram: A Method of Discrimination between Oceanic and Non-Oceanic Basalts. Earth and Planetary Science Letters, 24(3): 419–426 doi: 10.1016/0012-821X(75)90149-1 |
| Pearce, J. A., 1982. Trace Element Characteristics of Lavas from Destractive Plate Boundaries. In: Thorpe, R. S., ed., Andesites. Wiley, New York. 528–548 |
| Pearce, J. A., 1983. The Role of Subcontinental Lithosphere in Paragenesis at Destructive Plate Margins. In: Hawkesworth, C. J., Norry, M. J., eds., Continental Basalts and Mantle Xenoliths (Shiva Geology Series). Birkhäuser Boston, Boston. 230–249 |
| Pearce, J. A., Harris, N. B. W., Tindle, A. G., 1984. Trace Element Discrimination Diagrams for the Tectonic Interpretation of Granitic Rocks. Journal of Petrology, 25(4): 956–983 doi: 10.1093/petrology/25.4.956 |
| Peng, S. B., Li, C. N., Kusky, T. M., et al., 2010. The Discovery and Its Tectonic Significance of the Proterozoic Miaowan Ophiolites in the Southern Huangling Anticline Area, Western Hubei Province, China. Geological Bulletin of China, 29(1): 8–20 (in Chinese with English Abstract) http://www.researchgate.net/profile/Songbai_Peng2/publication/287557049_Discovery_and_its_tectonic_significance_of_the_Proterozoic_Miaowan_ophiolites_in_the_southern_Huangling_anticline_western_Hubei_China/links/596d790aa6fdcc03edb6ce80/Discovery-and-its-tectonic-significance-of-the-Proterozoic-Miaowan-ophiolites-in-the-southern-Huangling-anticline-western-Hubei-China.pdf |
| Peng, S. B., Kusky, T. M., Jiang, X. F., et al., 2012. Geology, Geochemistry and Geochronology of the Miaowan Ophiolite, Yangtze Craton: Implications for South China's Amalgamation History with the Rodinian Supercontinent. Gondwana Research, 21(2–3): 577–594 http://www.sciencedirect.com/science/article/pii/S1342937X11002024 |
| Robinson, P. T., Malpas, J., Dilek, Y., et al., 2008. The Significance of Sheeted Dike Complexes in Ophiolites. GSA Today, 18(11): 4–10 doi: 10.1130/GSATG22A.1 |
| Rollinson, H. R., 1993. Using Geochemical Data: Evaluation, Presentation, Interpretation. John Wiley & Sons, New York. 155 |
| Rollinson, H., 2009. New Models for the Genesis of Plagiogranites in the Oman Ophiolite. Lithos, 112(3–4): 603–614 http://www.onacademic.com/detail/journal_1000035065882310_c91b.html |
| Sun, S. S., McDonough, W. F., 1989. Chemical and Isotopic Systematics of Oceanic Basalts: Implications for Mantle Composition and Processes. In: Saunders, A. D., Norry, M. J., eds., Magmatism of the Ocean Basins. Geological Science of London Special Publication, 42: 313–345 |
| Wang, J. P., Kusky, T. M., Polat, A., et al., 2012. Sea-Floor Metamorphism Recorded in Epidosites from the ca. 1.0 Ga Miaowan Ophiolite, Huangling Anticline, China. Journal of Earth Science, 23(5): 696–704 doi: 10.1007/s12583-012-0288-8 |
| Wang, X. F., Chen, X. H., Zhang, R. J., et al., 2002. Precious Geological Relic Sits Protection and Archean-Mesozoic Multiple Stratigraphic Division and Sea Level Change along Yangtze River, Three Gorges Area. Geological Public House, Beijing (in Chinese with English Abstract) |
| Winchester, J. A., Floyd, P. A., 1977. Geochemical Discrimination of Different Magma Series and Their Differentiation Products Using Immobile Elements. Chemical Geology, 20: 325–343 doi: 10.1016/0009-2541(77)90057-2 |
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Hao Deng, Timothy M Kusky, Lu Wang, Songbai Peng, Xingfu Jiang, Junpeng Wang, Songjie Wang. Discovery of a Sheeted Dike Complex in the Northern Yangtze Craton and Its Implications for Craton Evolution. Journal of Earth Science, 2012, 23(5): 676-695. doi: 10.1007/s12583-012-0287-9
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