Ore Geology Reviews 64 (2015) 200–214

Contents lists available at ScienceDirect

Ore Geology Reviews

j ourna l homepage: www.e lsev ie r .com/ locate /oregeorev

Mineral chemistry of high-Mg diorites and skarn in the Han-Xing Irondeposits of South Taihang Mountains, China: Constraints onmineralization process

Ju-Quan Zhang a,c, Sheng-Rong Li a,b,⁎, M. Santosh b, Ji-Zhong Wang c, Qing Li a,b

a State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, 29 Xueyuan Road, Beijing 100083, Chinab School of Earth Sciences and Resources, China University of Geosciences Beijing, 29 Xueyuan Road, Beijing 100083, Chinac School of Gemology and Materials Technology, Shijiazhuang University of Economics, 136 Huaiandong Road, Shijiazhuang 050031, Hebei Province, China

⁎ Corresponding author at: State Key Laboratory of GeResources, China University of Geosciences, 29 XueyuaTel.: +86 10 8232 1732; fax: +86 10 8232 2176.

E-mail address: lisr@cugb.edu.cn (S.-R. Li).

http://dx.doi.org/10.1016/j.oregeorev.2014.07.0070169-1368/© 2014 Elsevier B.V. All rights reserved.

a b s t r a c t

a r t i c l e i n f o

Article history:Received 25 March 2014Received in revised form 19 June 2014Accepted 7 July 2014Available online 15 July 2014

Keywords:Mineral chemistryHigh-Mg dioriteAmphibole thermobarometerSkarn iron deposit

The Han-Xing region is located in the south Taihang Mountains (TM) in the central part of the North ChinaCraton, and is an important iron producing area. The iron deposits in this region are of skarn type, related to anEarly Cretaceous high-Mg diorite complex, including gabbro diorite, hornblende diorite, diorite, dioriteporphyrite, and monzonite. In this study we report the detailed mineral chemistry of the high-Mg diorites andskarn rocks. The olivine in the gabbro diorite shows chemical composition similar to that in mantle peridotitexenoliths. Clinopyroxene in the gabbro diorite is dominantly augite, with only minor diopside, whereas theclinopyroxenes in the diorite and monzonite are diopside. Amphiboles in the high-Mg diorites show composi-tional range from magnesiohornblende to magnesiohastingsite, with minor pargasite and tschermakite. Mostplagioclase in the high-Mg diorite is andesine and oligoclase. The magnesio-biotite in gabbro diorites showschemical characteristics of re-equilibrated primary biotites and those in calc-alkaline rocks. In the diorite anddiorite porphyrite, plagioclase shows complex chemical zoning. Clinopyroxene and garnet in skarn rocks showvarying FeO contents, the former containing low FeO (b9 wt.%) and occurring as the major skarn mineralin large-scale iron deposits, and the latter within small-scale iron deposits with high FeO (mostly N25 wt.%)content. We computed the pressure, temperature, oxygen fugacity and water contents based on the mineralchemistry of amphibole and biotite. Based on the results, the magma crystallization can be divided into twostages, one within the deep magma chamber, forming clinopyroxene, amphibole and plagioclase phenocrysts;the other after emplacement, forming the rim of phenocrysts and matrix minerals. The magma during theearly stage shows high temperature (~900 °C–950 °C), pressure (~300 MPa–500 MPa), relatively high logfO2

(NNO–NNO +2), and H2O content in melt (4%–8%). During the late stage, the magma temperature dropped toabout 750 °C, and pressure came down to less than 100 MPa, with the logfO2 rising to NNO+1–NNO +2.The zoning of amphibole and plagioclase records the process of magmamixing and crystallization, with injectionofmaficmagma into the felsicmagma chamber. The relatively high logfO2 andH2O content inhibitedpartitioningof iron intomafic minerals and favored concentration of Fe in themelt. Iron ore precipitation occurred when themagma was emplaced at shallow level, and was principally controlled by the chemical composition of carbonatewall rocks. The high logfO2, Fe3+ rich ore-forming fluid generated andradite and clinopyroxene when it reactedwith limestone and dolomitic limestone respectively.

ological Processes and Mineraln Road, Beijing 100083, China.

© 2014 Elsevier B.V. All rights reserved.

1. Introduction

The Han-Xing region is located in the southern part of the TaihangMountains (TM) in the central North China Craton, and is a well-known iron province containing numerous skarn iron deposits relatedto Early Cretaceous mafic-intermediate magmatic systems. Large-scale

mining has lasted for about 60 years, and a series of iron deposits hasbeen explored andmined such as the Xishimen, Beiminghe, Kuangshan,Qichun, and Fushan iron deposits, with a cumulative reserve of over1000 Mt (Zheng et al. 2007a).

Several earlier studies (e.g. Li et al., 2013; Niu et al., 1994; Shen et al.,1977, 1979, 1981; Shen et al., 2013a, 2013b; Xu, 1986, 1987; Zhanget al., 2013; Zheng et al., 2007a, b, c) addressed the genesis of theseiron deposits. Shen et al. (1977) and Xu (1986, 1987) examined thechemical composition and mineralogy of sodic metasomatites andother altered rocks and considered that magmatic fluids extracted theiron, potassium, calcium and magnesium from the diorite, and formed

201J.-Q. Zhang et al. / Ore Geology Reviews 64 (2015) 200–214

the skarn andmagnetitewhen it reactedwith theOrdovician carbonate.Liu et al. (1982) proposed that NaCl-rich fluids extracted andtransported the iron from diorite. Some other researchers (e.g. Niuet al., 1994; Zhen et al., 1984) believed that themetamorphic crystallinebasement contributed considerable iron to the ore formation. Recently,Li et al. (2013) and Shen et al. (2013a, 2013b) provided new data on Heand Ar isotopes, and suggested that significant crustal material was in-volved in the mineralization process. Since iron is a major element inthe various spheres of the earth, and occurs as a common constituentin several types of igneous, metamorphic and sedimentary rocks, it isoften difficult to precisely identify the source of iron. However, all theprevious studies in this region correlated the iron mineralization as abyproduct of Mesozoic magmatism (e.g., Shen et al., 2013a). This im-plies that the magmatic processes had an important relationship withthe iron mineralization.

Fig. 1. (a) Spatial distribution of Mesozoic igneous rocks in the eastern North China Craton

In this paper, we present results from a systematic study of thechemistry of minerals from high-Mg diorites and skarn, in an attemptto reconstruct the physico-chemical conditions of the mineralizationsystem. Based on regional geology, ore geology, and mineral chemistry,we propose a new genetic model of skarn iron deposits in the southernTM. This model not only provides insights into the chemical character-istics of the diorite-related mineralization, but also evaluates the pro-cess of evolution of the ore fluids from the magmatic to mineralizationstages.

2. Regional geology

Our study area is located in the central part of the North ChinaCraton (NCC) (Fig. 1a). The NCC is one of the fundamental Precambriannuclei in Asia (Li et al., 2013; Zhai and Santosh, 2011, 2013). The late

(modified from Yang et al., 2008); (b) detailed geological map of the Han-Xing region.

202 J.-Q. Zhang et al. / Ore Geology Reviews 64 (2015) 200–214

Archean–early Paleoproterozoic Fuping and Zanhuang Groups composethe basement of the central NCC in the TM (Li et al., 2013). The latteris the crystalline basement in the southern TM, composed of TTG(tonalite–trondhjemite–granodiorite) gneisses, andmonzonitic and po-tassic granite, with minor supracrustal rocks (Trapa et al., 2009; Xiaoet al., 2011; Yang et al., 2011, 2013). The Mesoproterozoic ChangchengGroup sandstone overlies the Zanhuang Group with an angular uncon-formity, and is in turn covered by Cambrian toOrdovician carbonate for-mation.Middle Ordovician limestone and dolomitic limestone comprisethewall rocks of the ore bodies (Niu et al., 1994; Shen et al., 1977, 1979,1981; Xu, 1986; Zheng et al., 2007a, b, c; Zhang et al, 2013). The easternsedimentary basins are covered by Carboniferous, Permian, and Triassicsandstone, mudstone, shale, and siltstone, with coal seams. The easternplain is covered by Tertiary sediments (Fig. 1b).

Mesozoic magmatism and regional structures (faults and folds)display NNE or NNW-trends. According to aeromagnetic data andfield observations, there are also four NWW-trending hidden faultswhich developed on the basement in this region and adjacent regions(Li, 1986; Zeng, 1987). The faults of basement and cover compose the

Fig. 2. (a) Cross section of the 28th exploration line of Baijian iron deposit;

main channels of magmatic emplacement (Ding, 1986; Xu and Lin,1989).

Diorite–monzonite–syenite series are the major magmatic rocktypes in the area among which the diorite and monzonite series areclosely associated with ore formation. In addition, some gabbroicrocks have also been reported in the diorite complex (Wang et al,2006). The intrusive rocks show high MgO, Cr, Ni, Sr and Ba contents,highly fractionated rare earth elements (REE), and strong Nb and Tadepletions (Qian and Hermann, 2010; Xu and Gao, 1990), and can bedivided into three belts (Li, 1986; Zheng et al., 2007a): the easternbelt (Hongshan pluton), central belt (Wuan pluton, Kuangshan pluton,Qichun pluton), and the western belt (Fushan pluton). Most of theimportant deposits occur in the central belt (Fig. 1b).

The K–Ar dating of whole rock and singlemineral (K-feldspar, horn-blende and biotite) from the different intrusions shows ages between150 and 64 Ma (Yang, 1982). Recent zircon U–Pb dating has yieldedages around 120–135Mawhere intrusive rocks of diverse compositionsshow similar ages (e.g. Chen et al., 2005, 2007, 2008; Li et al., 2013; Sunet al., 2014; Zhou and Chen, 2006).

(b) cross section of the 5th exploration line of Xishimen iron deposit.

203J.-Q. Zhang et al. / Ore Geology Reviews 64 (2015) 200–214

3. Mine geology

Most of the iron ore bodies, especially the large ones, are hosted byMiddle Ordovician carbonate and located in the central zone (Fig. 1b).These ore bodies show marked diversity in morphology and size andare controlled by the contact zones and faults within 100 m of the con-tact zones.

The ore bodies range in length from tens to hundreds of meters, anda few even exceed 5 km. They show several meters to tens of metersthickness, some exceeding 200m. There is significant variation in thick-ness within a short distance (e.g. Fig. 2a). Generally, the ore bodies oflarge and medium-sized deposits are relatively simple, mostly beddedor lenticular. The ore bodies of small deposits are more complex, withshapes ranging from ovoid to irregular (Zheng et al., 2007a), such asin the case of the Baijian and Xishimen iron deposits.

The ore bodies of Baijian iron deposit are controlled by the NS-trending Zhongguan–Baijian anticline. The ore bodies occupy the con-tact zone and faults within 300 m of limestone in the east limb ofanticline. The form of ore bodies is controlled by the contact zone andthe fracture in limestone, showing a NW-trend, extending for about1500mwith a width of 800 m (Zhang et al., 2013) (Fig. 2a). The dioriteporphyry and monzonite are the major intrusive rocks, and show in-tense alteration near the contact zone.

The Xishimen iron ore is the largest deposit in this region, with ironresource exceeding 120 Mt (Zheng et al., 2007b). The ore bodies inthis deposit mainly occur in the contact zone of Ordovician MajiagouFormation limestone and Yanshanian diorite and monzonite intrusivebodies (Fig. 2b). NNE–NE trending folds and NNE trending faults arethe main ore-controlling structure. Twenty eight magnetite ore bodieshave been identified, and most of these are layered, lenticular, ovoidor irregular in shape. The main ore body occurs at the contact zone,with a length of about 5020 m, thickness ranging from 1.2 to 32.0 mwith an average of 15.13 m, and maximum up to 103.42 m (Zhanget al., 2013; Zheng et al., 2007b).

The grade of ore varies from 30 to 50wt.% Fe. Oreminerals aremain-ly magnetite, followed by pyrite, martite, hematite, chalcopyrite and asmall amount of magnesian magnetite, pyrrhotite, bornite, chalcocite,goethite, etc. Gangue minerals are diopside and andradite, togetherwith tremolite–actinolite, phlogopite, serpentine, calcite, dolomite,and a small amount of magnesian olivine, humite, chlorite, scapolite,quartz, apatite, sphene, fluorite, zeolite etc.

Fig. 3. Photographs of the samples of gabbro diorite (a, b), hornblende diorite (c),

The common textures of the ores are euhedral and subhedral granu-lar, xenomorphic granular, reaction rim, and lattice-like. The structuresof ores include disseminated, massive, striped-banded, mottled, crystalcave, and brecciated.

Wall rock alteration is widely distributed in the mining area, andshows a close relationship with the ore bodies. Four stages of alterationare observed according tomineral assemblages andmetasomatism pro-ducing an albitized zone (albite + diopside + epidote + prehnite)close to the diorite, followed by the endoskarn zone (diopside +scapolite), the magnetite zone (magnetite + diopside + phlogopite)and the exoskarn zone (garnet/diopside + tremolite + actinolite +serpentine + calcite) within the marble host rock.

4. Sample description and analytical methods

4.1. Sampling and petrography

More than 600 samples of the different rocks were collected fromthe study area, from surface exposures, drill cores and undergroundmineworkings. The samples include gabbro diorite, hornblende diorite,diorite, diorite porphyrite, monzonite, skarn, ore and other alterationrocks. Representative samples of the intrusions, ores and skarns wereused for analytical studies. The main types of high-Mg diorite andskarn are described below.

The gabbro diorite intrudes into the high-Mg diorite (Fig. 3a) andshows porphyritic texture and dark-green color. The essential mineralsin this rock are clinopyroxene (15–20%), amphibole (25–30%), plagio-clase (40%) and biotite (5%), with minor olivine and K-feldspar (Figs. 3band 4a, b, c). The accessory minerals are ilmenite, titanomagnetite,magnetite, apatite, and zircon. The phenocrysts are clinopyroxene andamphibole, and the matrix is plagioclase. Clinopyroxene typicallyshows a reaction rim of amphibole, and the latter is altered to biotite.Olivine is altered to serpentine, and is associated with ilmenite.

The hornblende diorite is gray-green in color with medium grainedgranular porphyritic texture. The essentialminerals are amphibole (35–45%), plagioclase (~55%) (Figs. 3c and 4d, e, f), with minor K-feldspar.Accessory minerals include magnetite, apatite, zircon, and sphene.Zoning is common in amphibole (Fig. 4f).

Diorite and diorite porphyrite show medium grained, porphyritictexture, and gray-green color. The major minerals are amphibole(20–30%), plagioclase (~65–75%) ± biotite (5%), and minor K-feldspar,

diorite porphyrite (d), diorite (e) and monzonite (f) in the Han-Xing region.

Fig. 4. Representative photomicrographs ofmineral assemblages in themajor rock types of the Han-Xing area. Gabbro diorite (a–c), hornblende diorite (d–f), diorite (g–i), andmonzonite(j–l). Mineral abbreviations: Ol = olivine, Cpx = clinopyroxene, Am= Amphibole, Bt = Biotite, Pl = Plagioclase, Kfs = K-feldspar, Qtz = Quartz, Mag = Magnetite, Ilm = Ilmenite.

204 J.-Q. Zhang et al. / Ore Geology Reviews 64 (2015) 200–214

and clinopyroxene (Figs. 3d, e, and 4g, h, i). Accessoryminerals aremag-netite, apatite, zircon, and sphene. Plagioclase phenocrysts show com-plex zoning texture (Fig. 4h).

The monzonite shows fine-medium grained texture, gray-greencolor, and the main minerals are amphibole (15–20%), plagioclase(40–45%), K-feldspar (25%–30%), and quartz (5%) (Figs. 3f and 4j, k, l).The accessory minerals are magnetite, sphene, apatite, and zircon.

Garnet skarn occurs around the magnetite ore bodies. It showscoarse grained texture, and is associated with calcite and magnetite(Fig. 5a, b). Clinopyroxene skarn is common in Han-Xing iron deposits.It shows coarse grained texture, and is associated with magnetite ore(Fig. 5c, d). Clinopyroxene–scapolite skarn occurs in the inner contactzone, and shows coarse grained texture. Main minerals are scapolite(60–70%), clinopyroxene (15–25%) and magnetite (5–10%) (Fig. 5e).Clinopyroxene–hematite skarn occurs as minor veins, cutting the al-tered diorite, and shows coarse grained texture (Fig. 5f).

4.2. Analytical methods

Olivine, pyroxene, amphibole, biotite, plagioclase and K-feldsparfrom two gabbro diorite (Q-9 and XM-1), two hornblende diorite

(XX-8 and XX-1), two diorite (FD-1 and CY-1), and two monzonite(N803, B37) samples were analyzed for their major element composi-tion. The clinopyroxenes and garnets from skarn and ore were alsoanalyzed. The analyses were carried out with a JEOL JXA-8100 electronmicroprobe analyzer at Institute of Geology and Geophysics, ChineseAcademy of Sciences (IGG CAS) and a JEOL JXA-8230 electron micro-probe analyzer Institute of Mineral Resources, Chinese Academy ofGeological Science. Measurements were done under accelerating volt-age of 15 kV, a specimen current of 20 nA, and a 5 μm beam diameter.

5. Results

5.1. Minerals of high-Mg diorite

5.1.1. OlivineThe olivines in the gabbro diorite are mostly altered into serpentine.

Themineral chemical data showan FeO range of 15.56wt.%–20.26 wt.%,and a MgO range of 40.8 wt.%–44.2 wt.% (Supp. Table 1), similar tothe chemical compositions of olivine in peridotite xenoliths which areenclosed in high-Mg diorites (Huang and Xue, 1990a, 1990b; Xu andLin, 1991; Xu et al., 2003a, 2003b).

Fig. 5. (a) Field photo and (b) photomicrograph of garnet skarn, (c) field photo and (d), (e), (f) photomicrographs of clinopyroxene in ore and skarn. Mineral abbreviations: Mag =Magnetite, Cpx = Clinopyroxene, Grt = Garnet, Cal = Calcite, Hem = Hematite, Pl = Plagioclase, Scp = Scapolite.

205J.-Q. Zhang et al. / Ore Geology Reviews 64 (2015) 200–214

5.1.2. ClinopyroxeneThe clinopyroxenes in gabbro diorite, diorite and monzonite show

variable compositions and low Al2O3 (b3.7 wt.%), TiO2 (b0.4 wt.%)and Na2O (b1.4 wt.%) contents (Supp. Table 2). The pyroxene in gabbrodiorite (Q-9, XM-1) contains more Mg and Na than those in others, andmost of them are augite, with only few showing diopside composition(Fig. 6a). However, all the pyroxenes in the diorite and monzonite arediopside.

5.1.3. AmphiboleThe amphiboles in high-Mg diorites are generally euhedral pheno-

crysts, elongated and columnar. Some large phenocrysts show zoningtexture. A total of 59 points were analyzed in amphiboles from differenthigh-Mg diorite samples. The results show calcic amphibole composi-tions, following the classification scheme of Leake et al. (1997),with Ca ranging from 1.6 to 1.86 a.p.f.u. (atoms per formula unit). Theamphiboles are mainly magnesiohornblende and magnesiohastingsite,with a few belonging to pargasite and tschermakite (Fig. 6b, c, d;Supp. Table 3), similar to those reported by Niu and Zhang (2005) andQian and Hermann (2010).

The amphibole from different high-Mg diorites shows similar char-acteristics including high MgO and relatively low FeO contents. On the

basis of Al2O3 content, the amphiboles can be divided into two groups,the first group has high Al2O3, consisting of the phenocrysts; the secondgroup has relative low Al2O3 comprising the matrix or the rim of somephenocrysts. Some of these amphiboles also occur as reaction rims ofclinopyroxene.

5.1.4. BiotiteBiotite is rare in the high-Mg diorite of Han-Xing region. However,

the mineral is common in gabbro diorite, and substitutes amphibole(Fig. 4a, b). We analyzed 13 points in two samples. Among these,7 points are on biotites coexisting with amphiboles.

The results show MgO and FeO contents of 11.27–15.85 wt.% and13.83–18.39 wt.% (Supp. Table 4), respectively. Most of the biotitesbelong to magnesio-biotite (Fig. 7a), and show the chemical character-istics of re-equilibrated primary biotites (Fig. 7b) and biotites of calc-alkaline rocks (Fig. 7c).

5.1.5. FeldsparThe EPMA data show that most of the plagioclase in high-Mg diorite

is andesine and oligoclase (Fig. 8a; Supp. Table 5). In diorite, plagioclasealways shows complex chemical zoning, recording the history of evo-lution. The EPMA analyses show that some crystals have albite or

Fig. 6. Classification of minerals in the intrusive suite. (a) Pyroxene in gabbro diorite, diorite and monzonite (Morimoto et al., 1988). (b, c, d) Amphibole in gabbro diorite, hornblendediorite, diorite, diorite porphyrite and monzonite (Leake et al., 1997).

206 J.-Q. Zhang et al. / Ore Geology Reviews 64 (2015) 200–214

oligoclase rims and labradorite or andesine cores. We chose twocrystals in two different thin sections for detailed analysis. One isfrom diorite porphyrite (CY-1), the other is from diorite (FD-1).The plagioclase phenocrysts of diorite porphyrite are composed oftwo oscillatory zoned domains around a core, and an outer rim. TheAn (anorthite mol%) content of the core ranges from 24 mol% to37 mol%, showing an increasing trend in general, but that of the oscil-latory zoned domains shows a decrease from the inner portion to rim,ranging from 36 mol% to 18 mol%, and 29 mol% to 20 mol% respec-tively (Fig. 8c). The An content of rim shows an obvious change(29 mol%–31 mol%). The feldspar in diorite shows more complexzonings, with the An content showing rapid change across a few μm(from 29 mol% to 45 mol% in 30 μm) (Fig. 8b).

K-feldspar occurs in gabbro diorite, diorite andmonzonite. The albitecontent of K-feldspar in gabbro diorite (17 mol% to 26 mol%) is higherthan that in the other rocks (b10 mol%) (Fig. 8a).

5.2. Skarn minerals

5.2.1. ClinopyroxeneClinopyroxene has MgO and FeO contents of 12.88–17.27 wt.%

and 1.38–8.28 wt.% (Supp. Table 6), respectively. They show relativelyless FeO and Na2O, higher MgO, and CaO as compared with theclinopyroxene in high-Mg diorite. In Jo–Di–Hd diagram (Meinert et al.,2005), the composition falls in the field of clinopyroxenes from theiron deposits (Fig. 9a, b).

5.2.2. GarnetThe EPMA analyses of garnets show that andradite is themajor com-

ponent, with most grains having more than 90% (mol%) andradite. Fewsamples show relatively high grossular (b40.3 mol%) (Supp. Table 7).Their composition falls in the field of garnets from iron deposits in theSpess + Alm-Gross-And triangular diagram (Fig. 9c).

6. Discussion

6.1. The physico-chemical conditions of high-Mg dioritic magmacrystallization

6.1.1. GeothermobarometryIt has been established that the total Al content of hornblende in in-

termediate calc-alkaline rocks has a good correlation with pressure,based on which a number of geobarometers have been proposed tocalculate the pressure of crystallization (e.g. Hammarstrom and Zen,1986; Anderson and Smith, 1995; Hollister et al., 1987; Johnson andRutherford, 1989; Schmidt, 1992; Thomas and Ernst, 1990). However,the study of Ridolfi et al. (2008) showed that most of these barometersare inaccurate when compared to experimental results, with theaverage error as high as 280 MPa. Ridolfi et al. (2010) summarized theavailable experimental data, and proposed new thermobarometric for-mulations to calculate the pressure, temperature, oxygen fugacity andthe H2O content of magma. We calculated the physical–chemical pa-rameters of amphibole by a spreadsheet provided by Ridolfi et al.(2010).

The calculated results show that the amphibole formed in two dif-ferent stages. Most of the amphibole phenocrysts formed in a relativehigh pressure (200 MPa–600MPa) and high temperature (concentratedbetween 900 °C and 980 °C) stage, whereas the matrix or the rims ofphenocrysts formed in a lowpressure (b100MPa) and relative low tem-perature (concentrated between 700 °C and 800 °C) (Fig. 10a, Supp.Table 3) environment. Assuming a crustal density of 2700 kg/m3,the crystallization depth (in km) was computed. The results showthat most of the amphibole phenocrysts crystallized at a depth of10–20 km, and the maximum depth is estimated as 23 km. Theemplacement depth calculated by matrix amphibole or the rim of am-phibole phenocrysts ranges from 1.3 km to 3.3 km, withmost data clus-tered at 1.5 km to 2 km. This is consistent with the result calculated bythe stratigraphic thickness overlaid on intrusions.

Fig. 7. Compositional plots of biotites. The biotites from gabbro diorite are mainlyplotted in the magnesio-biotite field of Mg–(AlVI + Fe3++Ti)–(Fe2++Mn) ternarydiagram (a) (Foster, 1960), in the re-equilibrated primary biotite field of the 10 ∗ TiO2–

FeOtotal–MgO diagram (b) (Nachit et al., 2005), and in the field of calc-alkaline magmaof the MgO–FeO*–Al2O3 diagram (c) (Abdel-Rahman, 1994).

Fig. 8. Feldspar compositional plots. (a) Classification of feldspar in gabbro diorite,hornblende diorite, diorite, diorite porphyrite and monzonite. (b) Plagioclase phenocryst(central panel, photomicrograph on the right) of diorite (FD-1) showing complex zoning,with abrupt An variations. (c) Plagioclase phenocryst (central panel, photomicrograph onthe left) of diorite (CY-1) with sawtoothed zoning pattern.

207J.-Q. Zhang et al. / Ore Geology Reviews 64 (2015) 200–214

The biotite–amphibole P–T diagram (cited from Chen et al., 1993)and biotite Ti versus Mg/(Mg + Fe) diagram were also used (afterHenry et al., 2005) (Fig. 10d, e, f) to estimate the crystallization temper-ature and pressure. The results show that the gabbro diorite crystallizedat about 1 kbar, 700 °C–800 °C. This is highly consistentwith the resultscalculated from the amphiboles.

6.1.2. Oxygen fugacityThe study of Anderson and Smith (1995) shows that fO2 with fH2O

and total pressure is more important than temperature in controlling

the mafic silicate mineral chemistry. The Fe/(Fe + Mg) ratio of thesesilicates shows a significant negative correlation with fO2, and is inde-pendent of the Fe/Mg ratio of the whole rock. Several experimentalstudies (e.g. Bogaerts et al., 2006; Dall'Agnol et al., 1999; Martel et al.,1999; Pichavant et al., 2002; Prouteau and Scaillet, 2003; Scaillet andEvans, 1999) also suggested that fO2 exerts a dominant control on theFe/(Fe + Mg) ratio of the mafic silicates and the whole-rocks, at fixedtemperature. Therefore, the composition of amphibole and biotite inhigh-Mg diorite can be used to evaluate the redox conditions of intru-sive rocks in Han-Xing region.

The Fe/(Fe + Mg) ratios of amphiboles in the gabbro diorite(0.26–0.37), hornblende diorite (0.35–0.49), diorite (0.22–0.53) andmonzonite (0.26–0.44) are relatively low. Contrasting amphibolecompositions formed in the deep magma chamber and after emplace-ment respectively; our data show that the former has a greater rangeof variation (0.22–0.53), and the latter shows a relatively narrow

Fig. 9. (a) Classification of pyroxene from the Han-Xing skarn. (b) Jo–Di–Hd ternary showing the composition of pyroxenes. The compositional fields for pyroxene in Fe skarn deposits(Meinert et al., 2005) are shown in both diagrams for comparison. (c) Composition of garnet from the Han-Xing skarn. The compositional field for garnet in Fe skarn deposits is shownfor comparison (Meinert et al., 2005).

208 J.-Q. Zhang et al. / Ore Geology Reviews 64 (2015) 200–214

range (0.26–0.37). Based on amphibole Fe/(Fe +Mg) vs. AlIV diagrams(Fig. 11a) (Anderson and Smith, 1995), it can be interpreted that amphi-boles in the high-Mg diorite crystallized under high fO2 conditions, andthe fO2 after emplacement is higher than the value in the magmachamber.

Amphibole compositions have also been used to calculate fO2

following the method of Ridolfi et al. (2010). The results show thatlogfO2 range of NNO−0.35 to NNO+2.66, andmost values lie betweenNNO +0.50 and NNO +2.30. Without exception, logfO2 of gabbrodiorite (NNO +0.67–NNO +2.66), hornblende diorite (NNO −0.35–NNO +0.99), diorite (NNO −0.21–NNO +2.28) and monzonite(NNO −0.05–NNO +2.34) are in the stable range of magnetite. Frommagma chamber to the emplacement depth, logfO2 of magma showsan obvious increase (from average NNO +0.6 to NNO +2.1) (Fig. 10b,Supp. Table 3).

Fe3+/Fe2+ ratio of minerals is a robust indicator of the oxygen fu-gacity of magma. Fe3+/Fe2+ ratio of amphiboles in our study is mark-edly high, with most values in the range of 0.5–2.0. This confirmsa high fO2 for high-Mg diorite magma. The chemical compositions ofbiotite in the gabbro diorite are plotted in the Fe3+–Fe2+–Mg diagram(Wones and Eugster, 1965), and the results show a large range of

variations (Fig. 11b). Most of the plots fall in the field between theNi–NiO (NNO) and Fe2O3–Fe3O4 (HM) buffers, but two samples showslightly lower fO2, falling in the field between the Fe2SiO4–Fe3O4

(FMQ) and Ni–NiO (NNO) buffer. Four samples show even higher fO2,beyond the stable field of magnetite. We carefully examined the thinsections, and found that the samples with lower fO2 are associatedwith olivine xenocrysts and ilmenites. The olivine xenocrysts mayhave acted as a buffer when they broke down.

6.1.3. H2O contentsThe high content of in hornblende diorite (N40%) and high-Mg dio-

rite (10%–40%) indicates that themagma contained a high percentage ofwater. Ridolfi et al. (2010) identified that the AlVI in amphibole ismainlysensitive to water content in the melt, and offered a formulation tocalculate the water content. Following this method, we calculated thewater content of melt at the time of amphibole crystallization, andthe results show about 4 wt.%–7 wt.% water content in the melt in thedeep magma chamber, and about 2 wt.%–4.5 wt.% in themelt after em-placement (see Fig. 10c; Supp. Table 3). The gabbro diorite shows littlevariations (3 wt.%–5 wt.%) before and after the emplacement, but thehigh-Mg diorite shows relatively large variations.

Fig. 10. P–T (a), logfO2–T (b) and T–H2Omelt (c) diagrams for the calcic amphiboles inHan-Xing high-Mgdiorite calculated after Ridolfi et al. (2010). The curves and error bars in (a)–(c) arefrom Ridolfi et al. (2010). Error bars represent the expected uncertainty (σest) (22 °C) and maximum logfO2 errors (0.4 log unit). (a) and (c) display representative error bars indicatingthe variation in accuracy with P and H2Omelt. In the maximum relative P errors range from 11% (at the maximum thermal stability curve; black dotted line) to 25% (at the upper limit ofconsistent amphiboles; black dashed line). (b) shows the NNO, NNO +2 (from O'Neill and Pownceby, 1993) and MH curves (from Eugster and Wones, 1962). The maximum thermalstability (black dotted line) and the (lower) limit (black dashed line) of consistent amphiboles are also reported in (c) where the black and red error bars show the maximum relative error(15%) and rest (0.4 wt.%), respectively. (d) Plot of amphibole Ti/(Mg+Fe+Ti+Mn) vs biotite Ti/(Mg+Fe+Ti+Mn) diagram, (e) amphibole Al/(Al+Mg+Fe+Ti+Mn+Si) vs biotiteAl/(Al + Mg+ Fe + Ti +Mn+ Si) diagram (cited from Chen et al., 1993) and (f) Ti versus Mg/(Mg + Fe) for biotite (after Henry et al., 2005).

209J.-Q. Zhang et al. / Ore Geology Reviews 64 (2015) 200–214

Considering the pressure–temperature conditions derived from am-phibole chemistry, we infer that themagma emplacement processmusthave been rapid. This inference is also supported by the widespreadporphyritic texture in high-Mg diorite.When the water-richmagma in-truded from deep magma chamber to shallow crust, the reduction inpressure suddenly led to water exsolution from melt.

6.2. The genesis and evolution of high-Mg dioritic magma

The genesis of high-Mg diorites in this region has been the focus ofmany studies in the past (e.g. Chen et al., 2004, 2005, 2008; Luo et al.,1997, 2006; Qian and Hermann, 2010; Xu and Lin, 1989, 1991; Xuet al., 2009), with different explanations. Based on studies on thegabbroic rocks from this region and adjacent area, Wang et al. (2006)proposed that these rocks were generated from a refractory hydratedmantle, during a sudden change from a convergent to extensional

Fig. 11. (a) Amphibole Fe/(Fe + Mg) vs AlIV diagrams (Anderson and Smith, 1995) showingHan-Xing region. (b) Biotites from gabbro diorite plotted in the Fe3+–Fe2+–Mg diagram (Wo

regime in the central NCC at ~125 Ma. Xu et al. (2009) and Wanget al. (2011) believed that the high-Mg diorite forming by reaction ofmelt derived from a delaminated lower continental crust with perido-tite at mantle depth. Qian and Hermann (2010) proposed that theserocks were formed by the interaction of felsic magma with peridotiteat crustal depth. Chen et al. (2005, 2008) modeled the formationof the high-Mg diorite complex through partial melting of a depletedmantle source (asthenosphere) or an enriched mantle source (SCLM),with subsequent mixing of variable crustal components.

The chemistry of amphibole and biotite can be used to distinguishmagma sources. Almost all the data of the cores of amphibole pheno-crysts fall in the mantle source field, whereas most data of the matrixand rim of amphibole phenocrysts fall in the crust-mantle mixedsource field except those data from monzonite which fall in the crustsource field in the TiO2 versus Al2O3 diagram (Fig. 12a). All biotitecompositions lie in the crust–mantle mixed source field in a plot of

the possible oxygen fugacity conditions during the crystallization of high-Mg diorite ofnes and Eugster, 1965).

Fig. 12. (a) Plot of TiO2 versus Al2O3 for hornblende (after Jiang and An, 1984); (b) plot of TFeO/(TFeO+MgO) versusMgO for biotite (after Zhou, 1986); TFeO indicates total iron as FeO.

210 J.-Q. Zhang et al. / Ore Geology Reviews 64 (2015) 200–214

TFeO/(TFeO + MgO) versus MgO (Fig. 12b). These features implythat the high-Mg magma was derived from mantle and mixed withcrustal components during the crystallization process, which is con-sistent with the explanations from Sr–Nd–Pb isotopic results (Chenet al., 2004).

Magmamixingmay play an important role in the process of magmaevolution and ore mineralization (Li and Santosh, 2014; Li et al., 2014).By studying the complex zoning in plagioclases which is widespread inhigh-Mg diorites in Han-Xing area, we found that the chemical compo-nents vary greatly (sample CY-1 and FD-1). The FeO contents have sim-ilar variation with An, with an obvious correlation between increasedAn content and high Fe concentrations (Fig. 8b, c). This is explained asa sign of felsic magma mixing with more calcic magmas (RuprechtRuprecht and Wörner, 2007). Each abrupt rise of An compositionmight represent one pulse of magma mixing. After the mixing, themagma system changes from open to closed, leading to the crystalliza-tion of the plagioclase domains with smoothly decreasing An content.Our data show that this process occurred during multiple times,resulting in the complex oscillatory zoningpattern. The zoning in amphi-bole phenocrysts in the hornblende diorite also records this process. Wecomputed the P–T–logfO2 from the zoned amphiboles, and the resultsshow an abrupt rise of pressure, temperature, and a drop of ΔNNO,Fe3+/Fe2+, and Mg/(Mg + TFe) between two zones (Fig. 13). We con-sider this as a credible evidence for hot, low-logfO2, with mafic magmaintruding into the felsic magma chamber resulting in magma mixing.Chen et al. (2008) also found disequilibrium texture in plagioclase,

with high An cores (67–76) surrounded by low An rims (35–38), andconsidered the feature to be an evidence of magma mixing. Fromthe above discussion, we infer that mantle-derived mafic magma mi-grated from depth into the upper crust and invaded the felsic magmachamber. The gabbroic rocks containing mantle peridotite xenolithsalways occur as small intrusions or large xenoliths in other high-Mgdiorite, and their zircon U–Pb ages (~125 Ma) (Wang et al., 2006) areyounger than those of the diorites and monzonites (127–132 Ma)(Chen et al., 2005, 2007, 2008; Li et al., 2013; Sun et al., 2014; Zhouand Chen, 2006).

Fractional crystallization is one of the key processes for the forma-tion of high-Mg diorite and ore. Abundant amphibole phenocrystsformed in themagma chamber at a depth of 10–20 km. The porphyritictexture widely displayed by high-Mg diorite also indicates that exten-sive crystallization occurred before the magma emplacement. As themajor mafic mineral, the high MgO content of amphibole contributesto the high MgO content of the diorites.

From core to rim in a zoned amphibole (e.g. XX-1(1)-1 to XX-1(1)-2,XX-1(1)-3 to XX-1(1)-4, XX-1(1)-5 to XX-1(1)-6 in Fig. 13a), the valuesof ΔNNO, Fe3+/Fe2+, and Mg/(Mg + TFe) rise with the drop of P and T(Fig. 13b, c, d, e, f), suggestingmore iron residue in themelt under stablecrystallization process. The An content slowly declines in one of thezoned plagioclase illustrating increasing sodium in the melt after crys-tallization of amphibole and plagioclase. After emplacement, the rapidreduction of pressure and temperature led to the exsolution of water,and the formation of Na–Fe-rich ore-forming fluid. Thus, the plagioclase

Fig. 13. The compositional zoning of amphibole. (a) Photomicrograph of a zonedamphibole grain with the analytical domain marked by circle. (b), (c), (d), (e),(f) The pressure, temperature, ΔNNO, Fe3+/Fe2+ and Mg/(Mg + TFe) of differentsites in the zoned amphibole grain. The vertical gray bars show the position of bound-ary between the different compositional domains. See analytical data XX-1(1)-1 to 6 inSupp. Table 3.

211J.-Q. Zhang et al. / Ore Geology Reviews 64 (2015) 200–214

in thematrix is always albite, and sodicmetasomatism iswidely distrib-uted inside of the contact zone.

6.3. The influence of P–T–fO2 of ore-forming fluid on the mineralizationprocess

Magmatism to hydrothermalmineralization is a continuous process.The ore-forming fluids derived from magmas (Zheng, 2007), possesshigh temperatures and fO2. Homogenization temperature of melt-fluidinclusions in garnet and clinopyroxene is in the range of 580 °C–795 °C, and the data are consistent with the temperature of magmacrystallization in the late stage. The temperatures of ore-forming fluidvary from 204 °C–597 °C to 89 °C–389 °C (Zheng, 2007), obtained byhomogenization of fluid inclusions in garnet, clinopyroxene and calcite.The mineralization temperature ranges between 258 °C and 560 °C,with an average of 416 °C, obtained by decrepitation temperatures of14 magnetite samples (Zhang et al., 1996). The pressure decreasesfrom early stage of skarn to the late stage, varying from 52–130 MPato 12–25 MPa (Zheng, 2007).

The high fO2 of ore-forming fluid affects the skarn mineral chemis-try. The iron is mostly in the form of Fe3+ in high fO2 condition, andtherefore it is incorporated within garnet rather than clinopyroxene.The experimental studies on skarn mineral formation also show thatandradite forms in a more oxidizing condition than grossular (Liang,1994). The garnets from this study show high-content of andradite(always N90%), and the clinopyroxenes contain relative low FeO. Con-siderable iron gets into andradite leading to a decrease in the scale ofthemagnetite ore body. The geological scenario in our study area is con-sistent with this, and the andradite rich skarns carry only small scaleiron ores. Clinopyroxene is ubiquitously associated with the iron orebody, and occurs in the large iron deposits such as the Xishimen andBaijian deposits.

6.4. Metallogenic model

The metallogeny and magmatism in the Han-Xing region took placeduring 120–137 Ma (e.g. Chen et al., 2005, 2009; Li et al., 2013; Penget al., 2004; Shen et al., 2013a; Xu et al., 2009; Zheng et al., 2007c),which is consistentwith the timing of the large scaleMesozoicmagmat-ic event and related metallogeny in the North China Craton (e.g. Chenet al., 2007, 2009; Li et al., 2013; Mao et al., 2005, 2011), which arealso correlated to the destruction of the NCC (e.g., Gao et al., 2004,2009; Jiang et al., 2005; Wu et al., 2005; Xu et al., 2009; Zhu et al.,2012), Early Cretaceous magmatism and mineralization have alsobeen widely documented in several studies with the proposal thatthe lithospheric mantle under the eastern part of the NCC was under-going major changes during this stage (Guo et al., 2013, Li andSantosh, 2014). In the geodynamic setting of the destruction of theNCC, the lithosphere beneath the south TM became unstable, withmagma derived from mantle emplaced into the crust. Mg–Fe richmagmas were generated through complex magmamixing, assimilationand contamination. The continuum frommagma crystallization to min-eralization is summarized in the following stages: 1) low Fe/(Fe +Mg)ratio clinopyroxene and amphibole crystallized from high fO2 magma,and Fe was enriched in the residual melt; 2) partially crystallinewater-rich magma was emplaced rapidly, and Fe-rich fluid exsolvedfrom the magma with a decrease in water content; 3) high fO2 ore-forming fluid interacted with limestone and dolomitic limestone, andformed high-Fe garnet and low-Fe clinopyroxene, with the coeval for-mation of different iron ore bodies. The above processes are schemati-cally shown in Fig. 14.

7. Conclusion

(1) The crystallization process of high-Mg diorites can be dividedinto two stages based on the mineral chemistry of amphibole.

Fig. 14. (a) P–T conditions from magma crystallization stage to hydrothermal mineralization stage. The P–T conditions of magma crystallization are estimated by amphibolecomposition (see Fig. 6 b, c, d). The temperatures of skarn and mineralization are according to Zheng (2007) and Zhang et al. (1996), and the pressure is the average of the data obtainedby fluid inclusion (Zheng, 2007). (b) Schematic model of mineralization. See text for discussion.

212 J.-Q. Zhang et al. / Ore Geology Reviews 64 (2015) 200–214

The magma of early crystallization stage exhibits high tempera-ture (~900–950 °C), pressure (~300 MPa–500 MPa), relativelyhigh logfO2 (NNO–NNO +2), and H2O content in melt (~4%–8%). In the second phase, the temperature and pressure droppedto about 750 °C and less than 100 MPa respectively, logfO2

rise to NNO +1–NNO +2, and H2O content decreased to2 wt.%–4.5 wt.% in the late crystallization stage.

(2) The amphiboles are mainly magnesiohornblende andmagnesiohastingsite, and show high MgO and relatively lowFeO, formed under high logfO2 condition. The high logfO2 ofmagma does not promote iron being incorporated into themaficminerals, and Fe is concentrated in themelt, which formedthe iron ore when the magma was emplaced at shallow levels.

(3) High logfO2 iron-rich fluid reacted with limestone and dolomiticlimestone and formed andradite and clinopyroxene skarn re-spectively. The former containsmore Fe3+which is not favorablefor the formation of large scale iron deposits whereas the lattercontained little Fe2+ and occur as the main skarn mineral inlarge deposits.

Supplementary data to this article can be found online at http://dx.doi.org/10.1016/j.oregeorev.2014.07.007.

Acknowledgments

We thank Prof. Franco Pirajno, Editor-in-Chief and two referees fortheir helpful comments and corrections which improved our paper.Thanks are due to all the colleagues of the 11th Geological Brigade ofHebei province and Xishimen Iron Company for their help during thefield work. This work is supported by the Key Program of NationalNatural Science Foundation of China (Grand No. 90914002). Thisstudy also contributed to the 1000 Talent Award to M. Santosh fromthe Chinese Government.

References

Abdel-Rahman,A.M., 1994. Nature of biotites fromalkaline, calc-alkaline, and peraluminousmagmas. J. Petrol. 35, 525–541.

Anderson, J.L., Smith, D.R., 1995. Theeffects of temperature and fO2 on theAl-in-hornblendebarometer. Am. Mineral. 80, 549–559.

Bogaerts, M., Scaillet, B., Auwera, J.V., 2006. Phase equilibria of the Lyngdal granodiorite(Norway): implications for the origin of metaluminous ferroan granitoids. J. Petrol.47, 2405–2431.

Chen, G.Y., Sun, D.S., Zhou, X.R., Shao, W., Gong, R.T., Shao, Y., 107-140, 1993. Geneticmineralogy and gold mineralization of Guojialing granodiorite in Jiaodong region.China University Geosciences Pres (in Chinese with English abstract).

Chen, B., Jahn, B.M., Arakawa, Y., Zhai, M.G., 2004. Petrogenesis of the Mesozoic intrusivecomplexes from the southern Taihang Orogen, North China Craton: elemental andSr–Nd–Pb isotopic constraints. Contrib. Mineral. Petrol. 148, 489–501.

Chen, B., Tian, W., Zhai, M.G., Arakawa, Y., 2005. Zircon U–Pb geochronology and geo-chemistry of Mesozoic magmatism in the Taihang Mountains and other places ofthe North China Craton, with implications for petrogenesis and geodynamic setting.Acta Petrol. Sin. 21, 13–24 (in Chinese with English abstract).

Chen, Y.J., Chen, H.Y., Zaw, K., Pirajno, F., Zhang, Z.J., 2007. Geodynamic settings and tec-tonic model of skarn gold deposits in China: an overview. Ore Geol. Rev. 31, 139–169.

Chen, B., Tian, W., Jahn, B.M., Chen, Z.C., 2008. Zircon SHRIMP U–Pb ages and in-situ Hfisotopic analysis for the Mesozoic intrusions in South Taihang, North China Craton:evidence for hybridization between mantle-derived magmas and crustal compo-nents. Lithos 102, 118–137.

Chen, Y.J., Pirajno, F., Li, N., Qi, J.P., Guo, D.S., Lai, Y., Zhang, Y.H., 2009. Isotope systematics andfluid inclusion studies of the Qiyugou breccia pipe-hosted gold deposit, QinlingOrogen,Henan Province, China: implications for ore genesis. Ore Geol. Rev. 35, 245–261.

Dall'Agnol, R., Scaillet, B., Pichavant, M., 1999. An experimental study of a Lower Protero-zoic A-type granite from the eastern Amazonian Craton, Brazil. J. Petrol. 40 (11),1673–1698.

Ding, J.D., 1986. The metallogenic regularity and prognosis of the contact metasomatictype iron ore deposits in North China Plate area. Contrib. Geol. Miner. Resour. Res.1 (3), 18–28 (in Chinese with English abstract).

Eugster, H.P., Wones, D.R., 1962. Stability relations of the ferruginous biotite, annite.J. Petrol. 3, 82–125.

Foster, M.D., 1960. Interpretation of composition of trioctahedral micas. US Geol. Surv.Prof. Pap. 354B, 1–49.

Gao, S., Rudnick, R.L., Yuan, H.L., Liu, X.M., Liu, Y.S., Xu,W.L., Ling,W.L., Ayers, J., Wang, X.C.,Wang, Q.H., 2004. Recycling lower continental crust in theNorth China Craton. Nature432, 892–897.

Gao, S., Zhang, J.F., Xu, W.L., Liu, Y.S., 2009. Delamination and destruction of the NorthChina Craton. Chin. Sci. Bull. 54, 3367–3378.

Guo, P., Santosh, M., Li, S.R., 2013. Geodynamics of gold metallogeny in the ShandongProvince, NE China: a geological and geophysical perspective. Gondwana Res. 24(3–4), 1172–1202.

Hammarstrom, J.M., Zen, E., 1986. Aluminum in hornblende: an empirical igneousgeobarometer. Am. Mineral. 71, 1297–1313.

Henry, D.J., Guidotti, C.V., Thomoson, J.A., 2005. The Ti-saturation surface for low-to-medium pressure metapelitic biotites: implications for geothermometry and Ti-substitution mechanisms. Am. Mineral. 90, 316–328.

Hollister, L.S., Grissom, G.C., Peters, E.K., Stowell, H.H., Sisson, V.B., 1987. Confirmationof the empirical correlation of Al in hornblende with pressure of solidification ofcalc-alkaline plutons. Am. Mineral. 72, 231–239.

Huang, F.S., Xue, S.Z., 1990a. The petrographical and geochemical characteristics and gen-esis of the Han Xing intrusive complex. Acta Petrol. Mineral. 9, 203–212 (in Chinesewith English abstract).

Huang, F.S., Xue, S.Z., 1990b. The discovery of the mantle derived ultramific xenoliths inHandan Xingtai intrusive complex and their mineralogical–geochemical characteris-tics. Acta Petrol. Sin. 4, 40–45 (in Chinese with English abstract).

Jiang, C.Y., An, S.Y., 1984. On chemical characteristics of calcic amphiboles from igneousrocks and their petrogenesis significance. J. Mineral. Petrol. 3, 1–9 (in Chinese withEnglish abstract).

Jiang, Y.H., Jiang, S.Y., Zhao, K.D., Ni, P., Ling, H.F., Liu, D.Y., 2005. SHRIMP U-Pb zircondating for lamprophyre from Liaodong Peninsula: constraints on the initial time ofMesozoic lithosphere thinning beneath eastern China. Chin. Sci. Bull. 50, 2612–2620.

Johnson, M.C., Rutherford, M.J., 1989. Experimental calibration of the aluminum-in-hornblende geobarometer with application to Long Valley caldera (California)volcanic rocks. Geology 17, 837–841.

213J.-Q. Zhang et al. / Ore Geology Reviews 64 (2015) 200–214

Leake, B.E., Woolley, A.R., Arps, C.E.S., 1997. Nomenclature of amphiboles: report ofthe subcommittee on amphiboles of the International Mineralogical Association,commission on new minerals and mineral names. Can. Mineral. 35, 219–246.

Li, L.M., 1986. Discussion of Han-Xing type iron ore structural controlling factors. Geol.Prospect. 22 (4), 1–11 (in Chinese with English abstract).

Li, S.R., Santosh, M., 2014. Metallogeny and craton destruction: records from the NorthChina Craton. Ore Geol. Rev. 56, 376–414.

Li, S.R., Santosh, M., Zhang, H.F., Shen, J.F., Dong, G.C., Wang, J.Z., Zhang, J.Q., 2013. Inho-mogeneous lithospheric thinning in the central North China Craton: Zircon U–Pband S–He–Ar isotopic record from magmatism and metallogeny in the TaihangMountains. Gondwana Res. 23, 141–160.

Li, S.R., Santosh, M., Zhang, H.F., Luo, J.Y., Zhang, J.Q., Li, C.L., Song, J.Y., Zhang, X.B., 2014.Metallogeny in response to lithospheric thinning and craton destruction: geochemis-try and U–Pb zircon chronology of the Yixingzhai gold deposit, central North ChinaCraton. Ore Geol. Rev. 56, 457–471.

Liang, X.J., 1994. Garnets of Grossular-Andraditeseries: their characteristics andmetasomaticmechanism. Acta Petrol. Mineral. 13 (4), 342–352 (in Chinese with English abstract).

Lin, W.W., Peng, L.J., 1994. The estimation of Fe3+ and Fe2+ contents in amphibole andbiotite from EPMA data. J. Changchun Univ. Earth 24 (2), 155–162 (in Chinese withEnglish abstract).

Liu, Y.J., Li, Z.L., Zhao, M.F., Jiang, H.S., 1982. Experimental studies on the formation condi-tion of iron-ore deposits of Hanxing type inNorth China. J. NanjingUniv. (Nat. Sci. Ed.)4, 917–927 (in Chinese with English abstract).

Luo, Z.H., Deng, J.F., Zhao, G.C., Cao, Y.Q., 1997. Characteristics of magmatic activities andorogenic process of Taihangshan intraplate orogen. Earth Sci. J. China Univ. Geosci. 22,279–284 (in Chinese with English abstract).

Luo, Z.H., Wei, Y., Xin, H.T., Ke, S., Li, W.T., Li, D.D., Huang, J.X., 2006. The Mesozoic intra-plate orogeny of the Taihang Mountains and the thinning of the continental litho-sphere in North China. Earth Sci. Front. 13, 52–63 (in Chinese with English abstract).

Mao, J.W., Xie, G.Q., Zhang, Z.H., Li, X.F., Wang, Y.T., Zhang, C.Q., Li, Y.F., 2005. Mesozoiclarge-scale metallogenic pulses in North China and corresponding geodynamic set-tings. Acta Petrol. Sin. 21, 169–188 (in Chinese with English abstract).

Mao, J.W., Pirajno, F., Cook, N., 2011. Mesozoic metallogeny in East China and correspond-ing geodynamic settings— an introduction to the special issue. Ore Geol. Rev. 43, 1–7.

Martel, C., Pichavant, M., Holtz, F., Scaillet, B., Bourdier, J.L., Traineau, H., 1999. Effects offO2 and H2O on andesite phase relations between 2 and 4 kbar. J. Geophys. Res.104, 29453–29470.

Meinert, L.D., Dipple, G.M., Nicolescu, S., 2005. World skarn deposits. In: Hedenquist, J.W.,Thompson, J.F.H., Goldfarb, R.J., Richards, J.P. (Eds.), Economic Geology 100th Anni-versary Volume: Society of Economic Geologists, Littleton, Colorado, USA, IncludesSupplementary Appendices on CD-ROM (Filename: Meinert), pp. 299–336.

Morimoto, N., Fabries, J., Ferguson, A.K., Ginzburg, I.V., Ross, M., Seifert, F.A., Zussman, J.,Aoki, K., Gottardi, G., 1988. Nomenclature of pyroxenes. Mineral. Petrol. 39, 55–76.

Nachit, H., Ibhi, A., Abia, E.H., et al., 2005. Discrimination between primary magmatic bio-tites, reequilibrated biotites and neoformed biotites. Compt. Rendus Geosci. 337,1415–1420.

Niu, L.F., Zhang, H.F., 2005. Mineralogy and petrogenesis of amphiboles from intermedi-ate-mafic intrusions in southern Taihang Mountains. Geotecton. Metallog. 29 (2),269–277 (in Chinese with English abstract).

Niu, S.Y., Chen, L., Xu, C.S., et al., 1994. Crustal evolution and metallogenic regularities inTaihang mountain area. Seismological Press, Beijing, pp. 181–183 (in Chinese withEnglish abstract).

O’Neill, H.St.C., Pownceby, M.L., 1993. Thermodynamic data from redox reactions at hightemperatures. I. An experimental and theoretical assessment of the electrochemicalmethod using stabilized zirconia electrolytes, with revised values for the Fe-“FeO”,Co-CoO, Ni-NiO, and Cu-Cu2O oxygen buffers, and new data for the W-WO2 buffer.Contrib. Mineral. Petrol. 114, 296–314.

Peng, T.P., Wang, Y.J., Guo, F., Peng, B.X., 2004. SHRIMP zircon U-Pb geochronology of thediorites for southern TaihangMountains in the North China Interior and its petrogen-esis. Acta Petrol. Sin. 20, 1253–1262 (in Chinese with English abstract).

Pichavant, M., Martel, C., Bourdier, J.L., Scaillet, B., 2002. Physical conditions, structure,and dynamics of a zoned magma chamber: Mt. Peleé (Martinique, Lesser AntillesArc). J. Geophys. Res. 107. http://dx.doi.org/10.1029/2001JB000315.

Prouteau, G., Scaillet, B., 2003. Experimental constraints on the origin of the 1991Pinatubo dacite. J. Petrol. 44, 2203–2241.

Qian, Q., Hermann, J., 2010. Formation of high-Mg diorites through assimilation of perido-tite by monzodiorite magma at crustal depths. J. Petrol. 51 (7), 1381–1416.

Ridolfi, F., Puerini, M., Renzulli, A., Menna, M., Toulkeridis, T., 2008. The magmatic feedingsystem of El Reventador volcano (Sub-Andean zone, Ecuador) constrained by texture,mineralogy and thermobarometry of the 2002 erupted products. J. Volcanol.Geotherm. Res. 176, 94–106.

Ridolfi, F., Renzulli, A., Puerini, M., 2010. Stability and chemical equilibrium of amphibolein calc-alkaline magmas: an overview, new thermobarometric formulations andapplication to subduction-related volcanoes. Contrib. Mineral. Petrol. 160, 45–66.

Ruprecht Ruprecht, P.,Wörner, G., 2007. Variable regimes inmagma systems documentedin plagioclase zoning patterns: El Misti stratovolcano and Andahua monogeneticcones. J. Volcanol. Geotherm. Res. 165, 142–162.

Scaillet, B., Evans, B.W., 1999. The June 15, 1991, eruption of Mount Pinatubo: I. Phaseequilibria and pre-eruption P–T–fO2–fH2O conditions of the dacite magma. J. Petrol.40, 381–411.

Schmidt, M.W., 1992. Amphibole composition in tonalite as a function of pressure: an ex-perimental calibration of the Al-in-hornblende-barometer. Contrib. Mineral. Petrol.110, 304–310.

Shen, B.F., Lu, S.N., Yu, N.Z., Shan, L.F., Yu, J.H., 1977. The characteristics of sodium meta-somatism in magnetite deposits of a certain region and its prospecting significance.Sci. Geol. Sin. 3, 263–274 (in Chinese with English abstract).

Shen, B.F., Lu, S.N., Zhai, A.M., Li, Z.H., Yu, E.Z., 1979. The chemical component and itsgeological significance of magnetite in the iron deposits of contacting-metasomatic type in south Hebei. Geol. Rev. 25 (1), 10–18 (in Chinese withEnglish abstract).

Shen, B.F., Zhai, A.M., Li, Z.H., Wang, Y.L., 1981. The analysis of geological conditions formineralization of the iron deposits of Han-Xing subtype in south Hebei. Acta Geol.Sin. 2, 127–138 (in Chinese with English abstract).

Shen, J.F., Santosh, M., Li, S.R., Zhang, H.F., Yin, N., Dong, G.C., Wang, Y.J., Ma, G.G., Yu, H.J.,2013a. The Beiminghe skarn iron deposit, eastern China: geochronology, isotope geo-chemistry and implications for the destruction of the North China Craton. Lithos156–159, 218–229.

Shen, J.F., Li, S.R., Santosh, M., Meng, K., Dong, G.C., Wang, Y.J., Yin, N., Ma, G.G., Yu, H.J.,2013b. He–Ar isotope geochemistry of iron and gold deposits reveals heteroge-neous lithospheric destruction in the North China Craton. J. Asian Earth Sci. 78,237–247.

Sun, Y., Xiao, L., Zhu, D., Wu, T., Deng, X.D., Bai, M., Wen, G., 2014. Geochemical,geochronological, and Sr–Nd–Hf isotopic constraints on the petrogenesis of theQicun intrusive complex from the Handan–Xingtai district: implications for themechanism of lithospheric thinning of the North China Craton. Ore Geol. Rev. 57,363–374.

Thomas, W., Ernst, W.G., 1990. The aluminum content of hornblende in calc-alkalinegranitic rocks; a mineralogic barometer calibrated experimentally to 12 kbars. In:Spencer, R.J., Chou, I.-M. (Eds.), Fluid-mineral Interactions: A Tribute to H.P. Eugster.Geochem. Soc. Spec. Publ., 2, pp. 59–63.

Trapa, P., Faurea, M., Linb, W., Moniéc, P., Meffred, S., Melletona, J., 2009. The ZanhuangMassif, the second and eastern suture zone of the Paleoproterozoic Trans-NorthChina Orogen. Precambrian Res. 172 (1–2), 80–98.

Wang, Y.J., Fan, W.M., Zhang, H.F., Peng, T.P., 2006. Early Cretaceous gabbroic rocks fromthe TaihangMountains: implications for a paleosubduction-related lithosphericman-tle beneath the central North China Craton. Lithos 86, 281–302.

Wang, C.G., Xu, W.L., Wang, F., Yang, D.B., 2011. Petrogenesis of the Early CretaceousXi’anli hornblende-gabbros from the Southern Taihang Mountains: Evidence fromzircon U-Pb geochronology. Hf Isotope and whole-rock geochemistry. Earth Sci. J.China Univ. Geosci. 36 (3), 471–482 (in Chinese with English abstract).

Wones, D.R., Eugster, H.P., 1965. Stability of biotite-experiment theory and application.Am. Mineral. 50, 1228–1272.

Wu, F.Y., Lin, J.Q., Wilde, S.A., Sun, D.Y., Yang, J.H., 2005. Nature and significance of theEarly Cretaceous giant igneous event in eastern China. Earth Planet. Sci. Lett. 233,103–119.

Xiao, L.L., Wu, C.M., Zhao, G.C., Guo, J.H., Ren, L.D., 2011. Metamorphic P–T paths of theZanhuang amphibolites and metapelites: constraints on the tectonic evolution ofthe Paleoproterozoic Trans-North China Orogen Orogen. Int. J. Earth Sci. 100 (4),717–739.

Xu, X.F., 1986. Study on the formation of skarn iron deposit in the south Hebei from thetypomorphic characteristics of metasomatic alteration mineral. Contrib. Geol.Miner. Resour. Res. 1 (1), 50–56 (in Chinese with English abstract).

Xu, X.F., 1987. A tentative discussion on the formation of the Hanxing type iron depositsin the light of alteration mineralogy. Miner. Depos. 6 (3), 57–67 (in Chinese withEnglish abstract).

Xu, W.L., Gao, Y., 1990. Rare earth element geochemistry of intrusive rock series ofYanshan stage from Han-Xing district, Hebei province, China. Acta Petrol. Sin. 2,43–50 (in Chinese with English abstract).

Xu, W.L., Lin, J.Q., 1989. Petrogenesis of multiple Igneous rock series, Han-Xing district,Hebei province, China. J. Changchun Univ. Earth 19 (2), 149–186 (in Chinese withEnglish abstract).

Xu, W.L., Lin, J.Q., 1991. The discovery and study of mantle derived dunite inclusionsin hornblende–diorite in the Handan-Xingtai Area, Hebei. Acta Geol. Sin. 1, 30–41(in Chinese with English abstract).

Xu, W.L., Wang, D.Y., Gao, S., Lin, J.Q., 2003a. Discovery of dunite and pyroxenite xenolithsin Mesozoic diorite at Jinling, western Shandong and its significance. Chin. Sci. Bull.48, 1599–1604.

Xu, W.L., Wang, D.Y., Wang, Q.H., Lin, J.Q., 2003b. Petrology and geochemistry of twotypes of mantle-derived xenoliths in Mesozoic diorite from western Shandong prov-ince. Acta Petrol. Sin. 19, 623–636 (in Chinese with English abstract).

Xu, W.L., Yang, D.B., Pei, F.P., Wang, F., Wang, W., 2009. Mesozoic lithospheric mantlemodified by delaminated lower continental crust in the North China Craton:constraints from compositions of amphiboles from peridotite xenoliths. J. Jilin Univ.(Earth Sci. Ed.) 39, 606–617 (in Chinese with English abstract).

Yang, Z., 1982. The era of rocks and ores formation in eastern China skarn iron deposits.J. Geol. Inst. Metall. Ind. Minist. 1, 130–132 (in Chinese).

Yang, J.H., Wu, F.Y.,Wilde, S.A., Belousova, E., Griffin,W.L., 2008. Mesozoic decratonizationof the North China Block. Geology 36 (6), 467–470.

Yang, C.H., Du, L.L., Ren, L.D., Song, H.X., Xie, H.Q., Liu, Z.X., 2011. The age and petrogenesisof the Xuting granite in the Zanhuang Complex, Hebei Province: constraints on thestructural evolution of the Trans-North China Orogen, North China Craton. ActaPetrol. Sin. 27 (4), 1003–1016.

Yang, C.H., Du, L.L., Ren, L.D., Song, H.X., Wan, Y.S., Xie, H.Q., Geng, Y.S., 2013. Delineationof the ca. 2.7 Ga TTG gneisses in the Zanhuang Complex, North China Craton and itsgeological implications. J. Asian Earth Sci. 72 (10), 178–189.

Zeng, C.Q., 1987. An aeromagnetic study on the geological structure of the Handan-Xintaiiron mining district, Hebei. Geol. Prospect. 23 (9), 39–45 (in Chinese with Englishabstract).

Zhai, M.G., Santosh, M., 2011. The early Precambrian odyssey of the North China Craton:a synoptic overview. Gondwana Res. 20, 6–25.

Zhai, M.G., Santosh, M., 2013. Metallogeny of the North China Craton: link with secularchanges in the evolving Earth. Gondwana Res. 24 (1), 275–297.

214 J.-Q. Zhang et al. / Ore Geology Reviews 64 (2015) 200–214

Zhang, B.M., Zhao, G.L., Ma, G.X., 1996. The Metallogenetic System and Ore-formingModels of the Main Metallogenetic Belts in Hebei Province. Petroleum IndustrialPublishing House, Beijing, pp. 1–273 (in Chinese with English abstract).

Zhang, J.Q., Li, S.R., Wang, J.Z., Bai, M., Lu, J., Wei, H.F., Nie, X., Liu, H.M., 2013. The geneticmineralogical study of magnetite in Baijian and Xishimen skarn type of iron deposit,southern Hebei Province. Earth Sci. Front. 20 (3), 76–87 (in Chinese with Englishabstract).

Zhen, Y.Q., Ma, L.H., Li, Z.S., 1984. A probable correlation between the iron deposits ofAnshan type and Hanxing type. Earth Sci. 4, 71–80 (in Chinese with English abstract).

Zheng, J.M., 2007. The Ore-forming Fluid and Mineralization of Skarn Fe Deposits inHandan–Xingtai Area, South Hebei(Ph.D. thesis) China University of Geosciences,pp. 1–107 (in Chinese with English abstract).

Zheng, J.M., Mao, J.W., Chen, M.H., Li, G.D., Ban, C.Y., 2007a. Geological characteris-tics and metallogenic model of skarn iron deposits in the Handan–Xingtai area,southern Hebei, China. Geol. Bull. China 26 (2), 150–154 (in Chinese with Englishabstract).

Zheng, J.M., Xie, G.Q., Chen, M.H., Wang, S.M., Ban, C.Y., Du, J.L., 2007b. Pluton emplace-ment mechanism constraint on skarn Fe deposits in Handan–Xingtai area. MineralDeposits 26 (4), 481–486 (in Chinese with English abstract).

Zheng, J.M., Xie, G.Q., Liu, J., Chen, H.M., Wang, S.M., Guo, S.F., Gao, X., Li, G.D., 2007c.40Ar–39Ar dating of phlogopite from the Xishimen skarn iron deposit in theHandan–Xingtai area, southern Hebei, and its implications. Acta Petrol. Sin. 23(10), 2513–2518 (in Chinese with English abstract).

Zhou, Z.X., 1986. The origin of intrusive mass in Fengshandong, Hubei Province. ActaPetrol. Sin. 29 (1), 59–70 (in Chinese with English abstract).

Zhou, L., Chen, B., 2006. Petrogenesis and significance of the Hongshan syenitic pluton,South Taihang: zircon SHRIMP U–Pb age, chemical compositions and Sr–Nd isotopes.Prog. Nat. Sci. 116, 192–200 (in Chinese with English abstract).

Zhu, R.X., Yang, J.H., Wu, F.Y., 2012. Timing of destruction of the North China Craton.Lithos 49, 51–60.