Ore-forming age and tectonic setting of the Linjiasandaogou gold deposit in the Liaodong Peninsula, northeast China: constraints from geochronology and geochemistry

Xiaofeng Yao • Tingjie Yan • Zhicheng Lu¨ • Chenggui Lin • Kuifeng Mi •Shenghui Li • Yang Li • Wange Du

Abstract The Linjiasandaogou gold deposit is located in the Qingchengzi Orefield, North China Craton, China, and has not attracted many studies.We present geochronological, whole-rock geochemical, and Sr–Nd–Hf isotopic data to constrain the age and tectonic setting of the mineralization.U–Pb dating of zircon from pre-and post-ore dikes indicates the Linjiasandaogou Au deposit formed at ca.227–226 Ma.The granite porphyry (ca.227 Ma) and quartz diorite porphyry (ca.228 Ma), which are slightly older than the mineralization, have (87Sr/86Sr)i-= 0.7127–0.7162, εNd(t) = –13.7 to –17.0, and εHf(t) = –14.6 to –16.9, and display enrichment in light rare earth elements and large ion lithophile elements and depletion in high field strength elements.Two lamprophyres (226 and 225 Ma), which are slightly younger than the mineralization, have higher (87Sr/86Sr)i (0.7165–0.7216), negative εNd(t) (–11.2 to –14.3) and εHf(t) (–15.6 to –18.6) values,and are enriched in light rare earth elements but depleted in high field strength elements(Nb and Ta).The geochemical characteristics of the granitoid and lamprophyres indicate a lower crustal and enriched mantle source,respectively.We infer that the Linjiasandaogou Au deposit formed in a postcollisional tectonic setting,following the collision between the North China, Yangtze craton, and Central Asian Orogeny in Triassic.

Keywords North China craton ∙Qingchengzi ∙

1 Introduction

The Liaodong Peninsula is an important Au–polymetallic ore province in the North China Craton(NCC),China.The Qingchengzi orefield, located in the middle of the peninsula, contains ＞10 Pb–Zn deposits (e.g., Xiquegou, Nanshan, Zhenzigou, Diannan, Benshan, Erdaogou, and Taoyuan) and ca.10 Au–Ag deposits (e.g., Baiyun, Xiaotongjiapuzi, Linjiasandaogou, and Gaojiaopuzi).The orefield reserves are estimated at ca.15 Mt of Pb and Zn,2000 t of Ag, and 200 t of Au (Xu et al.2020).

Geochronological and geochemical studies have been carried out in the Qingchengzi orefield, particularly on the Baiyun Au deposit (Liu et al.2019a; Zhang et al.2019),Xiaotongjiapuzi Au deposit(Xue et al.2003;Yu et al.2009;Liu et al.2019b), and Zhenzigou Pb–Zn deposit (Ma et al.2016;Duan et al.2017).Four main ore-forming episodes for the orefield have been reported, Paleoproterozoic Pb–Zn mineralization (e.g.Zhenzigou deposit, Ma et al.2016),Triassic Au–Ag mineralization (e.g., Xiaotongjiapuzi deposit,Liu et al.2019b;Baiyun deposit,Liu et al.2019b),Jurassic Pb–Zn and Mo mineralization (e.g., Xiquegou Pb–Zn deposit, Xu et al.2020; Yaojiagou Mo deposit, Zhang et al.2016b), Cretaceous Au–Ag mineralization (e.g.,Baiyun deposit, Sun et al.2019a).The ore-forming ages of Pb–Zn and Au–Ag deposits in the Qingchengzi orefield are still in controversy, and the tectonic background of the regional mineralization is thus unclear.The Linjiasandaogou Au deposit is one of the four Au(Ag) deposits with gold reserves more than 15t in the orefield but rarely studied.In this paper, we describe the geological characteristics of the Linjiasandaogou Au deposit, and present geochronological,whole-rock geochemistry, and Sr–Nd–Hf isotope data for pre-and post-ore intrusions,in order to constrain the age of mineralization and provide implications for the tectonic setting of regional metallogenic events.

2 Geological setting

The NCC is the largest and oldest craton in China and contains ≥3.8 Ga crustal remnants (Liu et al.1992).The Liaodong Peninsula is located in the northeastern NCC.The basement of the Liaodong Peninsula consists of an Archean tonalite–trondhjemite–granodiorite (TTG) suite and Paleoproterozoic meta-sedimentary and -volcanic rocks.The Liaodong Peninsula records voluminous Mesozoic magmatism (Wu et al.2011).The northern Liaodong Peninsula has been affected by the collision with Central Asian Orogeny (CAO) and subduction of Mongolia–Okhotsk Plate since the Mesozoic.The Triassic tectonic evolution in the southern Liaodong Peninsula was somewhat linked to the collision between the NCC and Yangtze Craton, and breakoff of the subducting slab,delamination of the thicken continental crust or upwelling of asthenosphere might have caused the thinning of the NCC.(Chen et al.2003; Yang and Wu, 2009; Seo et al.2010; Wu and Zheng, 2013; Cheong et al.2015).The Liaodong Peninsula has also been indulged in tectonic evolution related to the subduction of the Pacific Plate since the mid-Mesozoic (Wu et al.2011; Zhou and Wilde,2013; Li and Yuen, 2014; Guo et al.2015).

The strata in the Qingchengzi orefield are dominated by the Paleoproterozoic Liaohe Group (Fig.1), which is divided into (from bottom to top) the Langzishan, Lieryu,Gaojiayu, Dashiqiao, and Gaixian formations.The Langzishan Formation comprises mica–quartz schists, garnet–kyanite–cordierite–mica schists, and gneisses.The Lieryu Formation comprises tourmaline–mica gneisses,magnetite–biotite gneisses, vermiculite–biotite gneisses,magnetite marbles, diopside–tremolite marbles, biotite–plagioclase gneisses, and meta-sandstones.The Gaojiayu Formation consists of biotite–plagioclase gneisses,garnet–mica schists, diopside–tremolite gneisses, amphibolites, and marbles.The Dashiqiao Formation consists of dolomitic marbles, banded micaceous marbles, tremolite marbles,garnet–mica schists, and wollastonite–mica schists.The Gaixian Formation comprises mica schists, wollastonite mica–schists,and garnet–mica schists.Ag–Au orebodies are mainly developed in the Gaixian Formation, while Pb–Zn orebodies occur mostly in the Dashiqiao Formation.

Granitic intrusions in the orefield comprise four groups:(1) Paleoproterozoic biotite granites, such as the Dadingzi pluton,with a zircon U–Pb age of c.1.7–1.6 Ga(Wang et al.2017); (2) Late Triassic granites, such as the Xinling and Shuangdinggou plutons, with zircon U–Pb ages of ca.226–218 Ma(Yu et al.2009;Duan et al.2017);(3)Middle Jurassic granodiorites, such as the Yaojiagou dike, with a zircon U–Pb age of 167 Ma (Zhang et al.2016b); and (4)Early Cretaceous intrusives, such as quartz porphyry and diorite dikes in the Baiyun deposit,with zircon U–Pb ages of ca.128–126 Ma (Sun et al.2019a).Moreover, NE–SWtrending lamprophyre dikes are often spatially associated with Pb–Zn, and Au–Ag orebodies(Yu et al.2009).Zircon U–Pb dating of lamprophyres in the southern Qingchengzi orefield have yielded a narrow range of ages from ca.227 to 210 Ma (Duan et al.2014).

The Qingchengzi orefield lies in a composite syncline–anticline system(Fig.1),in which there are NW–SE-,NE–SW-, and E–W-trending faults.The NW–SE-trending Jianshanzi Fault is spatially associated with Au–Ag deposits, while the NW–SE-trending Yushanggou Fault and NE–SW-trending F101 Fault are spatially associated with Pb–Zn deposits.Moreover, E–W-trending faults directly controlled the orebodies in the Baiyun deposit.

3 Ore deposit geology

3.1 Stratigraphy

The strata in the Linjiasandaogou deposit consist of the Gaixian Formation(Fig.1),which are mainly composed of mica schist, muscovite-biotite schist, sillimanite-mica schist and granulite.The protoliths in this formation were mudstone, argillaceous siltstone, and siltstone, which were metamorphosed to greenschist-to lower amphibolite-facies in the Paleoproterozoic(Yang et al.2019).More than 70%of the Au reserves occur in these schists.

Fig.1 a Tectonic sketch map showing the location of the Qingchengzi orefield (modified after Lin et al.2011).b Geological map of the Qingchengzi orefield (modified after Wang et al.2017)

3.2 Intrusions

Three types of intrusives are present in the Linjiasandaogou deposit:granite porphyry(GP),quartz diorite porphyry(QDP), and lamprophyre.Gold orebodies occur in GP and QDP.Some lamprophyres are also mineralized and altered,but some post-ore lamprophyres crosscut Au-bearing veins.

3.2.1 GP

The GP is light gray to white in color (Fig.2a).Phenocrysts comprise ca.25–30 % of the GP, and are mainly plagioclase (10–15 vol.%), K-feldspar (10 vol.%), and quartz(10–15 vol.%),with minor biotite(＜3 vol.%),and amphibole(＜2 vol.%)(Fig.2b).The matrix is felsic,finegrained, and dominated by K-feldspar (ca.25 vol.%),quartz (＞20 vol.%), and plagioclase (c.10 vol.%), with minor biotite(＜3 vol.%)and amphibole(＜2 vol.%).The accessory minerals are zircon + titanite + ilmenite ±apatite.

3.2.2 QDP

The QDP is light to dark gray (Fig.2c).Phenocrysts constitute ca.25–30 %of the QDP,and are mainly plagioclase(15–20 vol.%) and amphibole (10–20 vol.%), with lesser quartz (5–10 vol.%), K-feldspar (＜5 vol.%), and biotite(＜3 vol.%) (Fig.2d).The matrix is dioritic, fine-grained,and dominated by plagioclase (ca.20 vol.%), amphibole(ca.15 vol.%), and quartz (ca.10 vol.%), with minor K-feldspar(＜5 vol.%) and biotite (＜3 vol.%).Accessory minerals include zircon, apatite, ilmenite, and titanite.

Fig.2 Photographs and photomicrograph of the GP, QDP, and lamprophyre in the Linjiasandaogou deposit.a Photograph of the QP;b photomicrograph of the QP;c photograph of the QDP;d photomicrograph of the QDP;e photograph of the lamprophyre;f photomicrograph of the lamprophyre

3.2.3 Lamprophyre

The lamprophyres are grayish brown to gray-black(Fig.2e).They are typically porphyritic.The phenocrysts are mainly hornblende (10–15 vol.%), biotite (10–15 vol.%), and clinopyroxene (5–10 vol.%) (Fig.2f).The matrix consists of hornblende (25–30 vol.%), biotite(20–25 vol.%), and plagioclase (10–15 vol.%).Accessory minerals include apatite, magnetite, and titanite.

3.2.4 The sequence relationship of dikes and mineralization

The GP and QDP are both pre-ore dikes.Some gold lodes occurred in them with stockwork Au-bearing quartz-pyrite veins (Fig.3a, b) and alteration including silicification,chloritization, sericitization, epidotization, and carbonatization.Both pre-ore and post-ore lamprophyres developed in the deposit.The pre-ore lamprophyres are characterized by heavy alteration, pyrite mineralization, and structural fractured.The post-ore lamprophyres crosscut ore lodes or ore-bearing quartz veins, being relatively fresh and complete (Fig.3c, d).

Fig.3 Field photographs of sequence relationship among Au-bearing quartz veins, GP (a), QDP (b), and post-ore lamprophyres (c–d)

3.3 Structure

The Linjiasandaogou deposit is located in the south flat limb of the regional overturned syncline, which has an EW-trending and north-dipping axial plane.Some bedding faults occur but can only be observed underground.The faults are NE–SW-trending in the west and ENE–WSWtrending in the east, and are SE- or NW-trending with dip angles of 10°–20°.The fault zone are 0.2–5.0 m wide and show pinching and swelling.‘‘Z’’-type folding of the schistosity is evident in the fault zone.Induced secondary joints occur within GP in the hanging wall of the faults,and are commonly infilled by quartz.

3.4 Orebodies

The Linjiasandaogou deposit comprises altered rock-type(ca.90 % of reserve) and quartz vein-type (ca.10 % of reserve) lodes.Both types of lodes are generally related to bedding faults with small dip angles.The altered rock-type orebodies occur like manto (Fig.4), and sulfide minerals mainly develop along the schistosity of the Gaixian Formation.The alteration in the orebodies can be observed as silicification and sericitization.The quartz vein-type lodes occur where the faults cut GP and QDP, and sulfide minerals mainly develop in secondary joints within the fault zone.The major orebodies strike NE–SW or ENE–WSW,dip to the SE or S and NW or N at 10°–30°, and have lengths of ca.1100 m,widths of ca.990 m,and thicknesses of 0.5–11.7 m.

Fig.4 Cross-section of the 120 prospecting line through the Linjiasandaogou deposit

3.5 Ore mineralogy

The ore minerals include mainly pyrite and arsenopyrite(Fig.5), and minor pyrrhotite, chalcopyrite, galena, sphalerite, native Au, and electrum.Gangue minerals include mainly quartz, feldspars, biotite, and sericite, and minor calcite, chlorite, and epidote.Auriferous minerals occur mainly as inclusions in quartz,pyrite,and arsenopyrite,and in some cracks in these minerals (Dai et al.2006; Zhang et al.2012; Liu et al.2018).The occurrences of the auriferous minerals (native Au, electrum and ku¨stelite) as inclusion, fissure, and intercrystalline Au are 70 %, 25 %,and 5 %, respectively (Liu et al.2018).

Fig.5 Photographs and photomicrograph of ore in the Linjiasandaogou deposit.a Quartz vein-type ore; b alteration-type ore showing silicification; c euhedral to subhedral pyrite (Py); d arsenopyrite (Apy)

4 Sampling and analytical methods

4.1 Zircon U–Pb dating and Hf isotope analysis

Samples of mineralized GP, pre-ore QDP, and post-ore lamprophyre dikes were collected in the mine tunnel for geochronological and geochemical analysis.Zircons were separated using conventional heavy liquid and magnetic techniques before the individual zircons were examined under transmitted and reflected light and subjected to cathodoluminescence imaging to document their shapes and internal structures.

U–Pb dating of the samples LJ283-3 (lamprophyre),LJ323-1 (QDP), and LJ-1 (GP) were conducted by laser ablation–inductively coupled plasma–mass spectrometry(LA-ICP-MS) at the Wuhan Sample Solution Analytical Technology, Wuhan, China.Detailed operating conditions for the LA system and ICP-MS instrument, and data reduction, are the same as those described by Zong et al.(2017).Zircon 91,500 and glass NIST 610 were used as external standards for U–Pb dating and trace element calibration, respectively.U–Pb dating of sample LJ283-1(lamprophyre) was conducted by secondary ion mass spectrometry (SIMS) at the Analytical Laboratory of the Beijing Research Institute of Uranium Geology, Beijing,China.Measurements of U, Th, and Pb were conducted with a Cameca IMS-1280HR SIMS.U–Th–Pb isotope ratios and absolute abundances were determined relative to interspersed analyses of the standard zircon 91,500(Wiedenbeck et al.1995), using operating and data processing procedures similar to those described by Zong et al.(2010).Concordia diagrams and weighted-mean ages were produced using Isoplot/Ex_ver3 (Ludwig, 2003).

Zircon in situ Hf isotope analysis was carried out using a RESOlution SE 193 nm laser-ablation system attached to a Thermo Fisher Scientific Neptune Plus MC-ICP-MS at Beijing Createch Testing Technology Co., Ltd.Instrumental conditions and data acquisition protocols were described by Hou et al.(2007).A stationary spot used a beam diameter of ～38 μm.As the carrier gas, helium was used to transport the ablated sample from the laserablation cell to the MC-ICP-MS torch by a mixing chamber mixed with Argon.176Lu/175Lu = 0.02658 and176Yb/173Yb = 0.796218 ratios were determined to correct for the isobaric interferences of176Lu and176Yb on176Hf.For instrumental mass bias correction, Yb isotope ratios were normalized to172-Yb/173Yb = 1.35274 and Hf isotope ratios to179Hf/177Hf = 0.7325 using an exponential law.The mass bias behavior of Lu was assumed to follow that of Yb,and the mass bias correction protocol was described by Hou et al.(2007).

4.2 Geochemical and Sr–Nd isotopic analysis

Whole-rock major and trace element and Sr–Nd isotopic analyses were undertaken at the Analytical Laboratory of the Beijing Research Institute of Uranium Geology.Major elements were analyzed by X-ray fluorescence (XRF)spectrometry.Powdered samples of ca.0.5 g in weight were mixed with 5 g of Li2B4O7to make fused glass disks,which were then analyzed with an AXIOS Minerals XRF spectrometer.The accuracy of the major element analyses is ＜5%.Trace elements, including rare earth elements(REEs), were analyzed using a Finnigan Element ICP-MS after acid digestion of the samples in high-pressure Teflon bombs.The detailed analytical procedures are described in Qi et al.(2000), and the analytical precision was generally ＜5%.

Rb, Sr, Sm, Nd isotopic analysis were conducted using an IsoProbe-T thermal ionization mass spectrometer(TIMS).The measured87Sr/86Sr and143Nd/144Nd ratios were normalized to86Sr/88Sr = 0.1194 and146Nd/144Nd = 0.7219, respectively.87Sr/86Sr ratios of the SRM 987 Sr standard and143Nd/144Nd ratios of the JNDI-1 Nd standard obtained during this study were 0.710253 ± 0.00006 (2σ) and 0.512104 ± 0.00005 (2σ),respectively.

5 Results

5.1 Geochronology

± σ 207Pb/206Pb± σ 207Pb/235U± σ 50.0 109.2 101.8 242.6 145.4 474.1 101.8 138.9 94.4 768.5 100.9 86.1 129.6 254.6 112.9 150.0 129.6 188.9 113.9 105.5 187.0 95.4 75.0 41.7 133.3 124.1 216.7 239.0 209.3 122.3 233.4 653.7 233.4 220.4 239.0 431.5 220.4 205.6 220.4 350.1 209.3 231.6 213.0 250.1 213.0 213.0 220.4 211.2 194.5 209.3 211.2 211.2 7.0 8.8 9.6 24.0 12.4 38.5 9.3 12.2 7.8 29.8 8.1 8.0 10.8 17.0 10.2 13.4 11.4 14.1 10.1 8.8 15.2 7.8 6.8 6.4 11.2 11.8 228.1 227.5 228.2 229.2 229.3 226.1 227.7 229.3 227.9 229.1 228.5 228.9 229.1 227.9 228.1 228.9 228.5 229.4 227.6 226.7 227.2 227.4 226.6 227.8 225.6 227.6 2.7 2.8 3.0 6.9 4.2###3.5 3.0 2.7 8.5 2.9 3.0 3.5 6.1 4.0 4.7 4.5 5.7 4.1 3.0 3.4 2.2 2.3 2.3 3.2 3.3 76.8 170.3 120.4 86.1 239.0 257.5 276.0 205.6 7.0 13.8 9.8 7.8 226.9 228.0 228.7 226.1 2.6 3.9 3.4 2.4 Age (Ma)206Pb/238U 228.0 227.0 227.9 229.6 229.2 226.4 227.5 229.1 227.4 228.1 228.9 229.0 229.4 227.7 227.8 227.8 228.4 226.7 227.4 226.6 227.3 227.7 226.9 227.1 226.7 227.0 225.8 229.7 228.6 227.9± σ 0.0017 0.0024 0.0022 0.0056 0.0031 0.0158 0.0022 0.0030 0.0021 0.0104 0.0021 0.0020 0.0028 0.0061 0.0024 0.0033 0.0028 0.0042 0.0025 0.0023 0.0040 0.0020 0.0017 0.0016 0.0029 0.0027 0.0018 0.0038 0.0027 0.0020 Table 1 Zircon U–Pb age data for the GP, QDP, and lamprophyres from the Linjiasandaogou deposit Isotope ratio Th/U Element (ppm)Sample no 207Pb/206Pb± σ 207Pb/235U± σ 206Pb/238U U Th 0.0504 0.0510 0.0503 0.0483 0.0506 0.0614 0.0506 0.0505 0.0509 0.0555 0.0505 0.0502 0.0506 0.0535 0.0503 0.0508 0.0504 0.0512 0.0504 0.0504 0.0505 0.0502 0.0500 0.0503 0.0501 0.0501 0.0510 0.0513 0.0518 0.0503 0.0086 0.0109 0.0118 0.0296 0.0153 0.0474 0.0114 0.0151 0.0097 0.0368 0.0100 0.0099 0.0134 0.0209 0.0125 0.0165 0.0141 0.0174 0.0125 0.0108 0.0187 0.0096 0.0084 0.0079 0.0138 0.0145 0.0086 0.0170 0.0121 0.0096 0.2518 0.2511 0.2519 0.2533 0.2533 0.2494 0.2514 0.2534 0.2517 0.2531 0.2524 0.2529 0.2531 0.2516 0.2519 0.2528 0.2524 0.2535 0.2513 0.2502 0.2508 0.2510 0.2500 0.2516 0.2487 0.2512 0.2504 0.2517 0.2527 0.2494 0.0004 0.0005 0.0005 0.0011 0.0007 0.0020 0.0006 0.0005 0.0004 0.0014 0.0005 0.0005 0.0006 0.0010 0.0006 0.0008 0.0007 0.0009 0.0007 0.0005 0.0005 0.0004 0.0004 0.0004 0.0005 0.0005 0.0004 0.0006 0.0006 0.0004 0.0360 0.0358 0.0360 0.0363 0.0362 0.0357 0.0359 0.0362 0.0359 0.0360 0.0362 0.0362 0.0362 0.0360 0.0360 0.0360 0.0361 0.0358 0.0359 0.0358 0.0359 0.0360 0.0358 0.0358 0.0358 0.0358 0.0356 0.0363 0.0361 0.0360 0.47 0.59 0.25 0.65 0.38 0.57 0.68 0.64 0.62 0.60 0.44 0.66 0.46 0.58 0.48 0.44 0.43 0.49 0.65 0.52 0.52 0.61 0.58 0.59 0.58 0.44 0.68 1.88 0.92 0.90 4568 2308 3210 2433 2837 3282 3089 2788 2645 1177 2296 2823 1835 2204 1791 2677 2562 2222 2382 2086 2760 3521 2957 3208 2405 4496 1943 665 1303 2413 2150 1369 796 1575 1077 1862 2103 1784 1628 707 1008 1875 851 1277 864 1178 1092 1098 1543 1076 1431 2134 1707 1888 1390 1991 1329 1250 1205 2174 GP(LJ-1)1234 5678910111415 16171819202122 232425262728 QDP(LJ323-1)14 79

± σ 207Pb/206Pb± σ 207Pb/235U± σ 112.9 156.5 144.4 108.3 88.9 154.6 118.5 92.6 94.4 101.8 69.4 155.5 101.8 202.8 112.9 119.4 264.9 261.2 242.7 213.0 213.0 213.0 231.6 213.0 257.5 187.1 239.0 235.3 166.8 283.4 216.7 189.0 10.0 14.3 11.2 8.4 7.2 12.4 10.3 7.8 8.2 8.4 9.0 12.8 8.5 16.4 9.2 8.2 229.5 230.0 227.5 226.7 227.0 225.8 226.5 226.0 227.6 223.1 227.3 228.5 228.1 227.7 228.0 227.0 3.0 4.0 3.1 2.5 2.6 3.1 3.3 2.8 2.8 2.7 2.7 3.8 3.0 4.9 3.0 3.6 120.4 90.7 89.8 98.1 94.4 118.5 102.8 97.2 131.5 138.9 196.3 207.4 129.6 123.1 111.1 104.6 161.1 211.2 220.4 205.6 120.5 233.4 233.4 242.7 233.4 190.8 161.2 120.5 98.2 131.6 166.8 200.1 161.2 166.8 9.9 7.4 7.1 6.8 8.0 10.6 8.6 8.3 11.3 7.8 14.6 18.6 8.9 9.2 8.0 8.2 15.1 226.3 225.9 225.8 225.7 226.6 227.5 227.5 228.9 229.8 227.9 224.6 226.8 226.0 227.8 226.0 226.6 227.3 2.6 3.1 2.1 3.1 2.5 3.1 2.5 2.9 3.0 2.8 4.0 4.0 3.2 3.1 3.3 3.0 2.7 Age (Ma)206Pb/238U 227.6 226.8 227.7 228.6 227.3 226.4 225.7 227.7 226.0 228.6 226.7 228.7 227.9 227.5 227.0 229.8 226.9 226.1 226.7 228.1 225.5 224.6 224.0 225.8 227.4 225.8 227.5 226.7 225.9 226.1 227.2 227.6 227.8± σ 207Pb/206Pb± σ 207Pb/235U± σ 0.0025 0.0036 0.0032 0.0023 0.0020 0.0033 0.0026 0.0020 0.0021 0.0022 0.0023 0.0034 0.0022 0.0045 0.0025 0.0025 0.0515 0.0514 0.0510 0.0504 0.0504 0.0504 0.0508 0.0504 0.0514 0.0498 0.0510 0.0508 0.0492 0.0520 0.0505 0.0497 0.0123 0.0176 0.0139 0.0103 0.0089 0.0153 0.0127 0.0096 0.0102 0.0103 0.0111 0.0157 0.0105 0.0202 0.0114 0.0102 0.2536 0.2543 0.2511 0.2501 0.2505 0.2491 0.2499 0.2493 0.2513 0.2457 0.2509 0.2524 0.2519 0.2514 0.2518 0.2505 0.0005 0.0006 0.0005 0.0004 0.0004 0.0005 0.0005 0.0005 0.0005 0.0004 0.0004 0.0006 0.0005 0.0008 0.0005 0.0006 0.0026 0.0020 0.0019 0.0020 0.0021 0.0026 0.0022 0.0021 0.0028 0.0023 0.0043 0.0045 0.0028 0.0027 0.0023 0.0023 0.0038 0.0501 0.0506 0.0503 0.0484 0.0507 0.0506 0.0510 0.0506 0.0499 0.0493 0.0485 0.0480 0.0486 0.0492 0.0487 0.0493 0.0492 0.0121 0.0091 0.0088 0.0084 0.0098 0.0131 0.0106 0.0102 0.0139 0.0096 0.0180 0.0229 0.0110 0.0113 0.0099 0.0101 0.0186 0.2496 0.2492 0.2490 0.2489 0.2500 0.2511 0.2512 0.2529 0.2540 0.2516 0.2475 0.2503 0.2493 0.2515 0.2493 0.2501 0.2509 0.0004 0.0005 0.0003 0.0005 0.0004 0.0005 0.0004 0.0005 0.0005 0.0004 0.0007 0.0006 0.0005 0.0005 0.0005 0.0005 0.0004 Isotope ratio 206Pb/238U 0.0359 0.0358 0.0360 0.0361 0.0359 0.0357 0.0356 0.0360 0.0357 0.0361 0.0358 0.0361 0.0360 0.0359 0.0358 0.0363 0.0358 0.0357 0.0358 0.0360 0.0356 0.0355 0.0354 0.0356 0.0359 0.0357 0.0359 0.0358 0.0357 0.0357 0.0359 0.0359 0.0360 Th/U 0.75 0.67 0.69 0.86 0.84 0.78 0.96 0.86 0.97 1.07 0.63 0.94 0.72 0.89 1.11 0.69 1.11 0.90 0.80 1.08 0.69 0.74 1.19 0.81 0.80 0.42 0.84 0.63 0.75 0.68 0.67 0.63 0.90 Table 1 continued Element (ppm)Sample no U Th 1206 2010 575 1724 2267 879 1779 1270 1365 1411 1581 861 1914 739 1150 2148 5351 4129 4425 5926 2903 3805 2566 3296 2639 4736 3802 2551 3592 2577 3230 2700 4556 899 1350 399 1483 1896 686 1702 1091 1321 1514 1001 809 1385 660 1277 1473 5939 3731 3531 6408 2016 2821 3062 2666 2117 1994 3179 1619 2704 1752 2172 1703 4121 13 151617181920212223252627282930 Lamprophyre(LJ283-3)1456891012141617181920212223

± σ 207Pb/206Pb± σ 207Pb/235U± σ 125.9 74.1 89.8 172.3 220.4 253.8 10.3 6.8 7.6 226.7 227.7 227.6 3.6 2.7 3.2 43.5 30.1 37.7 23.4 34.4 36.1 39.4 34.1 39.1 63.5 60.8 37.7 30.9 57.8 207.9 256.0 187.8 225.5 208.1 177.3 289.0 269.6 243.4 268.2 237.0 192.4 250.1 407.5 5.2 4.9 4.6 3.9 6.5 4.7 5.2 5.2 4.6 8.0 6.8 4.5 4.2 8.9 224.6 228.3 222.2 230.3 221.7 225.3 225.4 228.1 223.6 225.4 232.3 218.6 225.7 346.4 3.8 4.4 3.6 3.6 6.4 3.8 4.0 4.5 3.3 6.0 4.2 3.5 3.5 4.8 Age (Ma)206Pb/238U 227.0 225.3 226.0 226.2 225.6 225.4 230.8 223.0 229.9 219.3 224.1 221.7 221.4 231.8 221.0 223.4 337.3± σ 207Pb/206Pb± σ 207Pb/235U± σ 0.0026 0.0016 0.0021 0.0496 0.0506 0.0513 0.0127 0.0084 0.0094 0.2501 0.2514 0.2513 0.0006 0.0004 0.0005 1.9001 1.3201 1.6386 1.0191 1.4992 1.5654 1.7471 1.5045 1.7177 2.8251 2.6869 1.6399 1.3539 2.6292 0.0503 0.0513 0.0498 0.0507 0.0503 0.0496 0.0521 0.0516 0.0511 0.0516 0.0509 0.0499 0.0512 0.0549 2.5639 2.3825 2.3090 1.8951 3.2685 2.3039 2.5491 2.5299 2.2877 3.9544 3.2510 2.2991 2.0867 3.0106 0.2476 0.2521 0.2446 0.2546 0.2440 0.2484 0.2485 0.2519 0.2464 0.2486 0.2571 0.2402 0.2489 0.4065 1.7214 1.9833 1.6268 1.5977 2.9044 1.6903 1.8562 2.0339 1.5109 2.7670 1.8302 1.6114 1.5878 1.4665 Isotope ratio 206Pb/238U 0.0358 0.0356 0.0357 0.0357 0.0356 0.0356 0.0364 0.0352 0.0363 0.0346 0.0354 0.0350 0.0349 0.0366 0.0349 0.0353 0.0537 Th/U 1.04 0.61 0.60 0.59 0.62 1.52 1.22 0.66 0.98 0.77 0.45 0.54 0.48 0.57 0.78 0.64 0.11 Table 1 continued Element (ppm)Sample no U Th 4581 3529 2208 3354 2865 1885 6240 2241 2813 1653 2542 2552 1767 1734 2056 3194 2002 4746 2166 1330 1977 1774 2870 7613 1471 2746 1272 1133 1372 850 985 1601 2059 264 24 2930 Lamprophyre(LJ283-1)12410111314151618202324 Plesovice

The analyzed zircons range from 70 to 140 μm in length(Fig.6).The zircons from the GP(LJ-1)and QDP(LJ323-1)are commonly elongated,and exhibit obvious oscillatory zoning (Fig.6),and have Th/U ratios(0.24–1.88; Table 1)consistent with igneous zircons (Corfu et al.2003).The analyzed zircons from lamprophyre(LJ283-3,LJ283-1)are mostly irregular granular with oscillatory zoning, fanshaped zoning, or fragmentized feature (Fig.6), and show no corroded or accreted rim.The zircons have Th/U ratios of 0.42–1.52(Table 1).Thus, the zircon U–Pb ages can be interpreted as representing the intrusion emplacement ages.Twenty-six zircon analyses of the GP (LJ-1) plot near the Concordia,and yielded a weighted-mean206Pb/238U age of 227.3 ± 1.3 Ma (MSWD = 0.067).Twenty zircon analyses of the QDP (LJ323-1) plot near the Concordia, and yielded a weighted-mean206Pb/238U age of 227.5 ± 1.3 Ma (MSWD = 0.14) (Fig.6a, b).Two samples (LJ283-3 and LJ283-1) of post-ore lamprophyre dikes yielded weighted-mean206Pb/238U ages of 226.3 ± 1.3 Ma(MSWD = 0.14) and 224.9 ± 2.4 Ma (MSWD = 0.78),respectively (Fig.6c, d).

Fig.6 Zircon U–Pb concordia and weighted-mean age diagrams,representative cathodoluminescence images of zircons for a pre-ore GP,b preore QDP, and c–d post-ore lamprophyres

Table 2 Major (wt.%) and trace element (ppm) contents of the GP, QDP, and lamprophyres from the Linjiasandaogou deposit

Table 2 continued

5.2 Major and trace element

Concentrations of major and trace elements for the samples are summarized in Table 2.The loss-on-ignition (LOI)values of the GP and QDP vary from 2.51–6.65 wt.%,reflecting slight alteration, whereas the LOI values of the lamprophyres vary from 12.35–16.62 wt.% due to their high volatile contents and some degree of alteration.The LOI value in the lamprophyre samples shows roughly correlations with some oxides (eg., K2O, Na2O, CaO) and easily fluid-mobile elements (e.g., Rb, Sr, Th, Ba) (not shown).However, the other oxides (e.g., MgO, P2O5,MnO, TiO2), compatible elements (e.g., Cr, Co, and Ni),and high-field-strength elements (HFSE; e.g., Nb, Zr, Hf,Ta), rare earth elements(REE),and Sr–Nd–Hf isotopes do not correlate with LOI (not shown).Therefore, these unrelated-to-LOI data are used for petro-genetic analysis.The LOI value of the sampled GP and QDP don’t correlate to oxides, all trace elements except Sr, and Sr–Nd–Hf isotopes (not shown).

Table 3 Sr and Nd isotopic data for the GP, QDP, and lamprophyres from the Linjiasandaogou deposit

The major element contents were recalculated on a volatile-free basis.In a SiO2vs.Zr/TiO2diagram(Fig.7a),data for the GP and QDP samples plot mainly in the andesite or dacite field, and data for the lamprophyre samples plot mainly in the alkaline basalt field.In a Y vs.Zr diagram (Fig.7b), data for all samples plot in the calcalkaline field.Primitive-mantle-normalized trace element patterns (Fig.8a) generally exhibit large-ion lithophile element(LILE)enrichment(e.g.,Rb,Th,and U)and highfield-strength element (HFSE) depletion (e.g., Nb, Ta, and Ti).The total REE contents of the GP, QDP, and lamprophyres vary from 187.38–257.13 ppm (average = 229.61 ppm), 470.52–506.86 ppm(average = 488.91 ppm), and 255.76–481.64 ppm (average = 340.21 ppm), respectively.The chondrite-normalized REE patterns (Fig.8b) are light REE enriched and exhibit small negative Eu anomalies (δEu = 0.82–1.03;average = 0.90).

Fig.7 Plots of a SiO2 vs.Zr/TiO2 (Winchester and Floyd, 1976) and b Y vs.Zr (Barrett and MacLean, 1994) for the QP, QDP, and lamprophyres

Fig.8 a Primitive-mantle-normalized trace element patterns and b chondrite-normalized rare earth element patterns for the QP, QDP, and lamprophyres.Chondrite and primitive mantle data were taken from Sun and McDonough (1989)

fLu/Hf TChur TDM2 TDM1 εHf(t)εHf(0)-0.98- 0.99- 0.98- 0.99- 0.99- 0.99- 0.99- 0.98 983 963 974 961 967 987 967 1004 2298 2278 2292 2278 2285 2312 2284 2331 1513 1493 1503 1490 1496 1512 1496 1529- 16.4- 16.1- 16.3- 16.1- 16.2- 16.6- 16.2- 16.9- 21.3- 21.0- 21.2- 21.0- 21.1- 21.6- 21.1- 21.8- 0.99- 0.99- 0.98- 0.99- 0.98- 0.99- 0.98- 0.98- 0.99- 0.99 935 902 936 890 931 974 921 918 926 927 2239 2195 2239 2182 2231 2296 2217 2214 2228 2234 1468 1440 1470 1427 1466 1501 1457 1455 1460 1460- 15.4- 14.7- 15.5- 14.6- 15.3- 16.4- 15.1- 15.1- 15.3- 15.4- 20.4- 19.7- 20.4- 19.5- 20.3- 21.3- 20.0- 20.0- 20.2- 20.3- 0.98- 0.97- 0.96- 0.98- 0.97- 0.99- 0.98- 0.98- 0.99- 0.98- 0.97- 0.99- 0.98- 0.99- 0.98 1047 1080 1100 1067 1079 1042 1020 1037 1023 1019 1094 970 1054 955 947 2387 2426 2433 2418 2418 2390 2352 2374 2362 2351 2434 2289 2400 2270 2250 1568 1598 1622 1583 1599 1560 1543 1558 1544 1542 1613 1498 1572 1485 1481- 17.8- 18.5- 18.6- 18.3- 18.4- 17.9- 17.3- 17.7- 17.5- 17.3- 18.6- 16.3- 18.0- 16.0- 15.6- 22.7- 23.3- 23.3- 23.2- 23.1- 22.7- 22.1- 22.5- 22.3- 22.1- 23.4- 21.2- 22.9- 20.9- 20.5 Table 4 Hf isotopic data for the GP, QDP, and lamprophyres from the Linjiasandaogou deposit 2σIHf 176Hf 177Hf 2σ 176Lu 177Hf 176Yb 177Hf Age (Ma)Sample no 0.282167 0.282176 0.282170 0.282176 0.282173 0.282160 0.282173 0.282152 0.282194 0.282214 0.282193 0.282219 0.282197 0.282168 0.282203 0.282205 0.282198 0.282196 0.282128 0.282110 0.282107 0.282114 0.282113 0.282127 0.282143 0.282133 0.282139 0.282143 0.282106 0.282171 0.282121 0.282180 0.282189 0.000010 0.000009 0.000009 0.000008 0.000009 0.000009 0.000009 0.000009 0.000013 0.000011 0.000012 0.000011 0.000011 0.000009 0.000010 0.000010 0.000009 0.000009 0.000009 0.000009 0.000010 0.000008 0.000010 0.000008 0.000009 0.000009 0.000009 0.000011 0.000011 0.000008 0.000009 0.000010 0.000010 0.282170 0.282178 0.282172 0.282178 0.282175 0.282162 0.282175 0.282154 0.282195 0.282215 0.282196 0.282220 0.282199 0.282170 0.282206 0.282207 0.282200 0.282197 0.282131 0.282114 0.282113 0.282116 0.282118 0.282129 0.282146 0.282136 0.282141 0.282146 0.282110 0.282173 0.282124 0.282182 0.282192 0.000007 0.000006 0.000004 0.000001 0.000005 0.000001 0.000004 0.000011 0.000012 0.000001 0.000006 0.000007 0.000005 0.000004 0.000017 0.000006 0.000004 0.000002 0.000019 0.000005 0.000022 0.000010 0.000010 0.000002 0.000015 0.000014 0.000001 0.000012 0.000008 0.000001 0.000004 0.000004 0.000006 0.000712 0.000472 0.000524 0.000395 0.000439 0.000419 0.000454 0.000569 0.000453 0.000418 0.000512 0.000263 0.000547 0.000378 0.000537 0.000529 0.000419 0.000293 0.000722 0.000882 0.001412 0.000610 0.001049 0.000460 0.000630 0.000674 0.000486 0.000610 0.001131 0.000429 0.000589 0.000407 0.000657 0.022056 0.012372 0.014389 0.010039 0.011375 0.010556 0.011493 0.014153 0.012933 0.011249 0.014240 0.007098 0.015325 0.010262 0.015029 0.014491 0.011544 0.007992 0.017099 0.020736 0.039869 0.013676 0.027975 0.010043 0.014206 0.017003 0.010837 0.014407 0.027214 0.010725 0.014026 0.010254 0.017109 228 228 228 228 228 228 228 228 228 228 228 228 228 228 228 228 228 228 225 225 225 225 225 225 225 225 225 227 227 227 227 227 227 GPLJ23-04 LJ23-06 LJ23 - 08 LJ23 - 09 LJ23 - 11 LJ23 - 12 LJ23 - 14 - 1 LJ23 - 18 QDP LJ323 - 1 - 07 LJ323 - 1 - 10 LJ323 - 1 - 14 LJ323 - 1 - 16 LJ323 - 1 - 17 LJ323 - 1 - 19 LJ323 - 1 - 20 LJ323 - 1 - 22 LJ323 - 1 - 26 LJ323 - 1 - 28 Lamprophyre LJ283 - 1 - 01 LJ283 - 1 - 05 LJ283 - 1 - 09 LJ283 - 1 - 12 LJ283 - 1 - 14 LJ283 - 1 - 16 LJ283 - 1 - 21 LJ283 - 1 - 23 LJ283 - 1 - 24 LJ283 - 3 - 03 LJ283 - 3 - 06 LJ283 - 3 - 16 LJ283 - 3 - 19 LJ283 - 3 - 20 LJ283 - 3 - 22

fLu/Hf TChur TDM2 TDM1 εHf(t)- 0.98- 0.98- 0.98- 0.98 1072 1072 1051 1030 2418 2427 2396 2366 1590 1587 1569 1551- 18.3- 18.5- 18.0- 17.5 Table 4 continued εHf(0)2σIHf 176Hf 177Hf 2σ 176Lu 177Hf 176Yb 177Hf Age (Ma)Sample no- 23.2- 23.4- 22.9- 22.4 0.282113 0.282109 0.282123 0.282136 0.000011 0.000010 0.000009 0.000009 0.000010 0.282117 0.282112 0.282126 0.282139 0.282294 0.000013 0.000004 0.000002 0.000013 0.000000 0.000777 0.000542 0.000583 0.000596 0.000270 0.019251 0.012748 0.014030 0.013495 0.007124 227 227 227 227 LJ283 - 3 - 24 LJ283 - 3 - 27 LJ283 - 3 - 28 LJ283 - 3 - 29 91,500

5.3 Sr–Nd-Hf isotopes

Whole-rock Sr–Nd isotopic data and zircon Hf isotopic data are listed in Table 3.The initial Sr, Nd, and Hf isotopic compositions were calculated using their weightedmean206Pb/238U ages.Samples of GP, QDP, and lamprophyre have nearly uniform (87Sr/86Sr)iratios of 0.7155–0.7162, 0.7127–0.7134, and 0.7165–0.7216, and εNd(t)values of–16.6 to–17.0,–13.7 to–16.8,and–11.2 to –14.3, respectively.Zircons from the GP, QDP, and lamprophyres have εHf(t) values of –16.1 to –16.9, –14.6 to –16.4, and –15.6 to –18.6, TDM1values of ca.1529–1490, 1501–1427, and 1622–1481 Ma, and TDM2values of ca.2331–2278, 2296–2182, and 2434–2250 Ma(Table 4), respectively.

6 Discussion

6.1 Ore-forming age of the Linjiasandaogou deposit

There is controversy regarding the ore-forming ages of Pb–Zn and Au–Ag deposits in the Qingchengzi orefield(Table 5).Previous studies have reported Pb–Zn mineralization ages of ca.221–226 Ma (Yu et al.2009; Duan et al.2017), 1798 ± 8 Ma (Ma et al.2016), and 151.8 ± 5.2(Xu et al.2020)by sphalerite and pyrite Rb–Sr dating.For the Au–Ag deposits, Triassic ages for the Xiaotongjiapuzi deposit (Xue et al.2003), ages of ca.230–210 Ma(Liu and Ai,2000;Zhang et al.2016a;Wang et al.2017; Liu et al.2019b) and ca.128–126 Ma (Sun et al.2019a) for the Baiyun deposit, and an age of 138.7 ± 4.1 Ma (Yu et al.2009) and 234 ± 14 Ma (Xue et al.2003) for the Gaojiapuzi deposit, have been reported.

Generally, it is more difficult to date lamprophyre by zircon U–Pb analysis than granite,because the protogenic zircons are easily mixed by zircons from magma sources or xenolith.The analyzed zircons from lamprophyre exhibit no obvious characteristics of inherited and xenolith zircons, e.g., corroded or accreted rim, U–Pb ages of several stages.The age of post-ore lamprophyre dikes in Linjiasandaogou deposit narrowed to 225–227 Ma,which lies in the age range (210–227 Ma) of lamprophyre in Qingchengzi orefield(Duan et al.2014;Sun et al.2019b).The ore formation age of ca.227–226 Ma in the Linjiasandaogou deposit can be limited by U–Pb dating of preore granitoid and post-ore lamprophyre dikes.As presented above, there is also late Triassic Pb–Zn mineralization reported.Moreover, Pb–Zn mineralization has a close relationship with the Au–Ag mineralization in the orefield.In the Gaojiapuzi and Xiaotongjiapuzi deposits,Pb–Zn and Au–Ag mineralization occurred along the same contact between schist and marble, with galena and sphalerite forming in marble and Au-and Ag-bearing minerals forming in schist (Wang et al., 2017; Zhang et al., 2020).Thus, the Linjiasandaogou deposit is an example of Triassic Pb–Zn–Au–Ag mineralization occurred in the Qingchengzi orefield.

6.2 Source of the felsic intrusives

Our data of the QDP, the presence of hornblende, variable SiO2(58.07–69.28 wt%) and MgO (0.92–1.92 wt%) contents, and variable A/CNK (0.94–1.11), are indicative of I-type granite.In addition, (87Sr/86Sr)(i)(0.7127–0.7134),εNd(t)(-13.7 to -16.8), and εHf(t)(-14.6 to -16.4) values of the QDP, suggest a crustal origin.The high La/Yb ratios(100.8–107.3)and low Gd/Yb ratios(7.1–7.7)imply garnet and amphibole in the residue (Drummond and Defant 1990).The negative Nb and Ti anomalies in the trace element spidergrams (Fig.8) can indicate that rutile is also in the residue (Green 1995).The TDM1ages of the QDP (1457–1501 Ma) (Fig.9) reveal that the partial melting source inherited the characteristics of the Paleoproterozoic basement.

The GP display high SiO2content (58.28–69.87 %),variable A/CNK (0.84–1.93), with (87Sr/86Sr)(i)(0.7155,0.7162), εNd(t)(-17.0, -16.6), and εHf(t)(-16.1 to-16.9)values.Their key elemental and isotopic indicators are similar in high extent to those of the QDP, which also imply a crustal origin.Their slightly right-dipping REE patterns, especially undiscriminating Eu anomalies of the GP (Fig.8), exclude a highly fractional and differentiated crustal source.The GP also has relatively high La/Yb ratios(73.8–92.5) and low Gd/Yb ratios (5.3–6.1), which imply garnet and amphibole are in the residue (Drummond and Defant 1990).But Ti partially shows negative anomalies in the trace element spidergrams (Fig.8), suggesting some rutile might be melted into magma (Green 1995).The TDM1ages of the QDP (1490–1529 Ma) imply a similar melting source to the QDP (Fig.9).

Fig.9 Plots of a zircon εHf(t)versus age(Ma)and b Hf model age histogram for the GP,QDP, and lamprophyres in the Linjiasandaogou deposit,lamprophyres in the Qingchengzi orefield (Duan et al.2014), granites of Shuangdinggou pluton (Duan et al.2014), and diabases from Liaodong Peninsula(Yang et al.2007).DM = depleted mantle;CHUR = chondritic uniform reservoir

Triassic intrusives in the Qingchengzi area have been previously reported.Triassic granites, such as the Shuangdinggou pluton (ca.224–218 Ma; Duan et al.2012, 2014; Xie et al.2018) and the Xinling pluton (ca.226–225 Ma; Xie et al.2018), are considered to be the result of partial melting of the lower crust (Wang et al.2017; Xie et al.2018).Moreover, the Shuangdinggou pluton was considered to be mixed by mafic magma originating from the lithospheric mantle, which was indicated by field occurrence of mafic enclaves and high Nb/Ta ratios(Duan et al.2014).Granite from Shuangdinggou, GP, and QDP has similar Hf and Nd isotopic characteristics, but different Sr isotopic compositions (Figs.9 and 10).In the εNd(t)vs.(87Sr/86Sr)tdiagram (Fig.10), granite from Shuangdinggou is close to the EMI while GP is close to the EMII, and QDP is among them.Given that GP and QDP were altered to some extent,their Sr isotopic compositions can barely be used to detect their origin.But their similar REE patterns,Nd and Hf isotopic characteristics,generally imply the same source with the Shuandinggou pluton.

6.3 Source of the lamprophyres

Lamprophyres are generally considered to be the products of small degree partial melting of the enriched subcontinental lithospheric mantle (SCLM) (McKenzie 1989;Fowler and Henney 1996; Chen and Zhai 2003).The lamprophyres in the Linjiasandaogou deposit have major and trace element characteristics (e.g., low SiO2contents,elevated MgO, and compatible element contents), which are consistent with a mantle source.However,they are also enriched in some incompatible elements such as light REEs and depleted in HFSEs (Nb and Ta), and have high (87-Sr/86Sr)(t)(0.7165–0.7216), negative εNd(t)(-11.2 to-14.3) and εHf(t)(-15.6 to -18.6) values.It might be originated from the enriched mantle, or from a depleted mantle with the incorporation of crustal materials.Lamprophyres’TDM1ages narrowed in 1481–1622 Ma,the lack of correlation between SiO2and TiO2, P2O5, Nb, Ta, (87-Sr/86Sr)t, εNd(t), rule out the possibilities of huge crustal contamination.In an εNd(t) vs.(87Sr/86Sr)tdiagram(Fig.10),the lamprophyres have an EMII signature similar to the lithospheric mantle of the NCC.The lamprophyre in the Qingchengzi was considered to derive from subduction modified fertile lithospheric mantle beneath North China Craton(Duan et al 2014).We also proposed that the source of the lamprophyres is probably generated from the lithospheric mantle of the NCC.

Fig.10 Plot of initial 87Sr/86Sr vs.εNd(t) for the GP, QDP, and lamprophyres in the Linjiasandaogou Au deposit, granites of Shuangdinggou pluton (Duan et al.2014), and diabases from Liaodong Peninsula (Yang et al.2007).Data for Precambrian basement from Liaodong Peninsula are from Sun et al.(1992), Wu et al.(1997), and Wan et al.(1999)

6.4 The tectonic setting implication

Four types of Triassic intrusives in the region can be identified: (1) mafic dikes from an enriched mantle source(Yang et al.2007; Yang and Wu, 2009; Duan et al.2014);(2)mafic dikes and enclaves from a depleted mantle source(Yang et al.2007;Yang and Wu,2009;Xie et al.2018);(3)granites from a lower crustal source(Duan et al.2012;Xie et al.2018);(4)nepheline syenites from an enriched mantle source (Yang et al.2007; Zhu et al.2017).Based on the geochronological data and magma petrogenesis discussed above, it can be found that QDP and GP are of the third type and the lamprophyres are most like the first type.

In the early Mesozoic, the evolution of the NCC was affected by the northward collision of the Yangtze Craton in the south and the collision of the CAO in the north.The Sulu–Dabie high-pressure and ultrahigh-pressure metamorphic belt represents the collision between the NCC and Yangtze Craton from ca.244–225 Ma (Yang and Wu,2009; Wu and Zheng, 2013; Zhao et al.2018).Numerous quartz monzonite and monzogranite intrusions with zircon U–Pb ages of ca.254–237 Ma are present in the northern NCC.Notably, alkaline granitoid emplaced from ca.230–200 Ma in northeast China(e.g.,Saima pluton;30 km from the Qingchengzi orefield) are indicative of a postcollisional tectonic setting (Zhang et al., 2009; Seo et al.2010; Wu et al.2011; Wang et al.2012; Ouyang et al.2013).Furthermore, Xu et al.(2009) also argued that the tectonic setting of the CAO switched to an extensional environment during ca.217–201 Ma in northeast China,based on the geochemistry of volcanic rocks.We conclude that the Linjiasandaogou deposit formed in a post-collisional setting, which involved interaction between lithosphere mantle and crust (Fig.11).The Triassic collisional events thickened the lower crust, partly delaminated the lithosphere, and induced asthenospheric upwelling and melting of the lower crust and underlying mantle, which generated the pre-ore and post-ore intrusions in the Linjiasandaogou deposit.

Fig.11 Schematic model for Au mineralization in a post-collisional setting in the Triassic.NCC = North China Craton;YC = Yangtze Craton;CAO = Central Asian Orogeny

7 Conclusions

The Linjiasandaogou ore deposit was formed at 227–226 Ma.The nearly coeval intrusive were derived from the lower crust with some mantle materials input.The episode of Triassic Pb–Zn–Au–Ag mineralization occurred in the Qingchengzi orefield in a post-collisional tectonic setting,following the collision between the NCC,southern Yangtze Craton, and northern CAO.Lithospheric delamination and asthenospheric upwelling generated the magmatism and associated Au deposits.

AcknowledgementsThis study was jointly supported by the National Key Research and Development Program of China (Grant Nos.2018YFC0603806 and 2017YFC0601506),the National Natural Science Foundation of China (Grant No.41902101), and the Geological Survey Program of China (Grant No.DD20190166).Assistance from Liu Fuxing and Wu Dianjun is much appreciated.

Declarations

Conflict of interestThe authors declared that they have no conflicts of interest to this work.