Early Mesozoic tectonic transition of the eastern South China Block: constraints from Late Triassic Dashuang complex in eastern Zhejiang Province

ABSTRACT

The Mesozoic tectonic transition from the Palaeo-Tethys tectonic regime to the Palaeo-Pacific tectonic regime in the eastern South China Block has long been debated. Geochemical and zircon U–Pb–Hf isotopic studies were conducted on the Dashuang complex in the eastern Zhejiang Province. The Dashuang complex consists mainly of quartz syenite in the northwestern part and quartz monzonite in the southeastern part. New laser ablation inductively coupled plasma mass spectrometry zircon U–Pb data show that the quartz syenite, the quartz monzonite, and its chilled margin (fine-grained granite) crystallized at 235 ± 4 Ma, 232 ± 3 Ma, and 230 ± 1 Ma, respectively. The Dashuang complex intrudes into the Chencai Group gneiss that postdated ~646 Ma and underwent anatexis at 443 ± 14 Ma. The quartz monzonite shows A-type granite affinity, characterized by high K₂O + Na₂O and Zr + Nb + Ce + Y, high FeO_T/(MgO + FeO_T) and Ga/Al ratios, an enrichment in light rare earth elements, and depletions in Ba, Sr, and Eu. The quartz monzonite has zircon ε_Hf(t) values of ?14.2 to –11.9 and two-stage model ages of 1788–1922 Ma. Zircon ε_Hf(t) values of the chilled margin (fine-grained granite) and wall rock (gneiss) are scattered (?18.2 to –6.3 and ?19.5 to 10.2). The corresponding two-stage model ages are 1482–2133 Ma and 1184–2471 Ma, respectively. The Dashuang complex was derived mainly from partial melting of Neoproterozoic clastic rocks in the Cathaysia Block. Geochemical data indicate that the quartz monzonite formed in a post-collision extensional environment. These results, considered with previous data, indicate that the transition from the Palaeo-Tethys to the Palaeo-Pacific tectonic regimes of the eastern South China Block occurred during the Late Triassic (225–215 Ma).     

Listvenite-related gold deposits of the South Urals (Russia): A review

The Urals is a complex fold belt, which underwent long geological evolution. The formation of most gold deposits in the Urals is related to the collision stage. In this paper, we review some relatively small listvenite-related gold deposits, which are confined to the large Main Uralian fault zone and some smaller faults within the Magnitogorsk zone. The Mechnikovskoe, Altyn-Tash, and Ganeevskoe deposits are studied in detail in this contribution. They comprise the ore clusters along with other numerous small gold deposits, and constituted the sources for the gold placers exploited in historical time. The gold is hosted by metasomatites (listvenites, beresites) and quartz veins with economic gold grades (up to 20 g/t Au). Listvenites are developed after serpentinites and composed of quartz, fuchsite, and carbonates (magnesite, dolomite) ± albite. Volcanic and volcanoclastic rocks are altered to beresites, consisting of sericite, carbonates (dolomite, ankerite), quartz and albite. Pyrite and chalcopyrite are major ore minerals associated with gold; pyrrhotite, Ni sulfides, galena, sphalerite, arsenopyrite and Au-Ag tellurides are subordinate and rare. Gold in these deposits is mostly high-fineness (>900‰). The lower fineness (∼800‰) is typical of gold in assemblage with polymetallic sulfides and tellurides. The ores have been formed from the NaCl–CO₂–H₂O ± CH₄ fluids of low (∼2 wt% NaCl-equiv.) to moderate (8–16 wt% NaCl-equiv.) salinity at temperatures of 210–330 °C. The oxygen isotopic composition of quartz (δ¹⁸O) varies from 14.7 to 15.4‰ (Mechnikovskoe deposit), 13.2 to 13.6‰ (Altyn-Tash deposit) and 12.0 to 12.7‰ (Ganeevskoe deposit). The oxygen isotopic composition of albite from altered rocks of the Ganeevskoe deposit is 10.1‰. The calculated δ¹⁸O_H2O values of the fluid in equilibrium with quartz are in a range of 5.7–6.3, 4.2–4.6 and 6.3–6.7‰ respectively, and most likely indicate a magmatic fluid source.     

The Sr isotopic characterization and Pb-Pb age of carbonate rocks from the Satka formation,the Lower Riphean Burzyan Group of the southern Urals

The Rb-Sr and U-Pb systematics are studied in carbonate deposits of the Satka and Suran formations corresponding to middle horizons of the Lower Riphean Burzyan Group in the Taratash and Yamantau anticlinoria, respectively, the southern Urals. The least altered rock samples retaining the ⁸⁷Sr/⁸⁶Sr ratio of sedimentation basin have been selected for analysis using the original method of leaching the secondary carbonate phases and based on strict geochemical criteria of the retentivity (Mn/Sr < 0.2, Fe/Sr < 5 and Mg/Ca < 0.024). The stepwise dissolution in 0.5 N HBr has been used to enrich samples in the primary carbonate phase before the Pb-Pb dating. Three (L-4 to L-6) of seven consecutive carbonate fractions obtained by the step-wise leaching are most enriched in the primary carbonate (in terms of the U-Pb systematics). In the ²⁰⁶Pb/²⁰⁴Pb-²⁰⁷Pb/²⁰⁴Pb diagram, data points of these fractions plot along an isochron determining age of 1550 ± 30 Ma (MSWD = 0.7) for the upper member of the Satka Formation. The initial ⁸⁷Sr/⁸⁶Sr ratio in the least altered limestones of this formation is within the range of 0.70460–0.70480. Generalization of the Sr isotopic data published for the Riphean carbonates from different continents showed that 1650–1350 Ma ago the ⁸⁷Sr/⁸⁶Sr ratio in the world ocean was low, slightly ranging from 0.70456 to 0.70494 and suggesting the prevalent impact of mantle flux.     

Geochronology and Geochemistry of the Xingxingxia Triassic A-type Granites in Central Tianshan, NW China: Petrogenesis and Tectonic Implications

The Triassic granitoids in Central Tianshan play a key role in determining the petrogenesis and tectonic evolution on the southern margin of the Central Asian orogenic belt. In this study, we present SHRIMP zircon U-Pb ages, Hf isotopic and geochemical data on the Xingxingxia biotite granite, amazonite granite and granitic pegmatite in Central Tianshan, NW China. Zircon U-Pb dating yielded formation ages of 242 Ma for the biotite granite and 240 Ma for the amazonite granite. These granitoid rocks have high K2O with low MgO and CaO contents. They are enriched in Nb, Ta, Hf and Y, while being depleted in Ba and Sr, showing flat HREE patterns and negative Eu anomalies. They have typical A-type granite geochemical signatures with high Ga/Al (8–13) and TFeO/(TFeO + MgO) ratios, showing an A2 affinity for biotite granite and an A1 affinity for amazonite granite and granitic pegmatite. Zircon εHf(t) values of the granitoids are 0.45–2.66, with Hf model ages of 0.99–1.17 Ga. This suggests that these A-type granites originated from partial melting of the lower crust. We propose that Xingxingxia Triassic A-type granites formed under lithospheric extension from post-orogenic to anorogenic intraplate settings and NE-trending regional strike-slip fault-controlled magma emplacement in the upper crust.     

内蒙古科尔沁右翼中旗三叠纪花岗质岩锆石U-Pb年龄、地球化学特征及其地质意义

笔者对内蒙古科尔沁右翼中旗代钦塔拉地区出露的花岗质岩进行了锆石U-Pb定年和岩石地球化学研究,旨在探讨该区花岗岩成因类型和区域构造演化。研究区的花岗质岩主要以黑云母花岗岩和花岗闪长岩为主,岩石明显富SiO₂、Al₂O₃和碱质,属于过铝质高钾钙碱性系列的S型花岗岩;稀土元素标准化配分图总体呈轻稀土富集、重稀土亏损特点,LREE/HREE的值为3.12~16.17,平均为10.07;La_N/Yb_N为2.72~28.71,具中等程度的负Eu异常;岩石富集大离子亲石元素Rb、K、Pb,亏损高场强元素Nb、Ta、Zr、Ce、Ti,具碰撞型花岗岩的特征。依据地球化学特征可将花岗岩划为低Sr低Yb型,说明花岗岩可能是在较高的压力下形成的。锆石U-Pb年龄为(242.6±2.5)Ma,表明该区古亚洲洋的俯冲碰撞发生在三叠纪,花岗岩体的形成与碰撞拼合有关。     

华南地区三叠纪矿床地质特征、成矿规律和矿床模型

华南以中生代成矿大爆发为特征,燕山期矿床成矿规律的研究程度较高,近年来发现越来越多的三叠纪矿床,但三叠纪矿床的分布规律和矿床模型是值得关注的重要科学问题。本文基于最新研究成果,论述华南三叠纪矿床地质特征和矿床类型,提出成矿规律,初步地建立成矿动力学模型。华南地区三叠纪矿床分布较为广泛,目前确定的46个三叠纪矿床分布于5个区带,形成于晚三叠世 (230~200 Ma),被划分为花岗岩有关的钨锡多金属矿床、侵入岩有关的远端金锑矿床、卡林型金矿床和MVT型铅锌矿床4种主要类型。在空间上,华南三叠纪矿床存在成矿元素分带性,由西向东依次为MVT型铅锌矿床、卡林型金矿床、侵入岩有关的远端金锑矿床、花岗岩有关的钨锡多金属矿床。华南5个成矿区带普遍存在印支期和燕山期的叠加成矿作用,在南岭西段桂北苗儿山—越城岭和滇东南老君山地区还发育加里东和印支期的叠加成矿作用。     

湖南水口山花岗闪长岩的地球化学特征及成因

中生代花岗质岩石在华南分布广泛,且常与W-Sn、Pb-Zn等金属矿床具有紧密的时空联系,而湖南水口山花岗闪长岩是与Pb-Zn成矿作用有关的典型代表。与华南改造型花岗岩相比,水口山花岗闪长岩及其成矿作用的研究程度较低。本文系统研究了该花岗闪长岩的岩相学特征、主元素、微量元素和Sr-Nd同位素组成,重点讨论了其岩石成因类型、物质来源及形成的构造环境。研究结果表明,水口山花岗闪长岩为贫Si O2、富碱、富铁镁、准铝质-弱过铝质的高钾钙碱性岩;表现出轻稀土元素富集,轻重稀土分馏强烈,弱负Eu异常;不相容元素Ba、Ta、Nb、Sr、Ti亏损,而Rb、Th、U、K、LREE相对富集的特征。岩体的(87Sr/86Sr)i比值为0.707364~0.711380,εNd(t)值为–6.61~–2.40,具明显的亏损地幔和华南上地壳混合特征。水口山花岗闪长岩的矿物组成、元素地球化学和同位素地球化学特征均表明,该岩体为同熔型花岗岩。该岩体是在晚中生代由太平洋板块向欧亚大陆板块俯冲诱发的华南板块伸展-减薄构造环境下,玄武质岩浆上涌,底侵中下地壳,与中上地壳混合形成的燕山早期高钾钙碱性花岗岩。     

Geochemical and isotopic evidence for the age,orogenic setting and petrogenesis of the Nychum Volcanic association,North Queensland

Rb‐Sr and K‐Ar age determinations agree with palaeobotanical evidence in assigning an age of 270 Ma (Lower Permian) to the Nychum Volcanics, North Queensland. Geological and geochemical evidence (moderate ‐REE, La/Yb, Th, Zr/Y, Hf/Yb, Sc/Ni) indicate that the volcanics were erupted on a thin, active continental margin. Five magma groups are present: high‐alumina basalts, andesite‐dacites, acid rocks, tholeiitic andesites, and pitchstone with a high La/Yb ratio. The high‐alumina basalts and calc‐alkaline andesites have a parent‐daughter (source rock‐partial melt) relationship. The acid rocks share high HREE, Zr, Hf, Zn, Sc, Fe/Mg and low Al with, and may be fractionated from, the tholeiitic subduction‐zone andesites. Low‐pressure fractional crystallisation is evident in all five magma groups.     

Geochemical Characteristics and Tectonic Significance of Triassic Granite from Taer Region, the Northern Margin of West Kunlun

Late Hercynian-early Indosinian (Triassic) granite is widely distributed around the Taer region of the northern margin of West Kunlun. The rock mass is mainly composed of calc-alkaline porphyroid biotite adamellite and characterized by SiO2-rich, high-Ca, moderate-alkaline, and strongly peraluminous attributes, and relatively low ΣREE with LREE enrichment and a moderate Eu anomaly. As shown in the trace element spider web diagram, distinct peaks appear for Th, La, Nd, and Zr and clearly low values appear for Ba, Nb, Sr, P, and Ti. Further, compared with the primitive mantle, Rb/Sr and Rb/Ba are considerably higher and Nd/Th and Nb/Ta are relative low, all falling into the scope of the crust-origin rocks, indicating the characteristics of the crust-origin S-type granite. The rock mass’s zircon U-Pb isotopic age is determined to be 235.7 ± 3.9 Ma. On the basis of the age data, spatio-temporal location, lithology, and geochemistry of the rock mass, we conclude that the formation of the rock mass is closely related to the strong compressional orogenic movement (240 Ma) of the Tianshuihai terrane and the South Kunlun terrane. The rock mass is the product of the collision orogenic movement. However, distinct differences are observed between the studied rock mass and the synorogenic Bulunkou rock mass, which may be caused by the different collision strength and different positions with respect to the collision zone.     

西藏羌塘达尔应强过铝花岗岩地球化学特征及地球动力学意义

羌塘地块中部达尔应首次发现强过铝质的二云母碱长花岗岩、白云母碱长花岗岩、电气石白云母碱长花岗岩,通过地球化学研究显示其SiO₂、Al₂O₃和K₂O质量分数均很高,以高铝、低镁铁为特征,A/CNK比值大于1.1,属典型的含白云母强过铝质花岗岩。稀土元素总量为(10.65~100.02)×10^-6,配分曲线显示铕负异常明显。Nb、P、Ti等高场强元素具有负异常,而Rb、Th、Y等大离子亲石元素具有明显的正异常。岩浆源区可能以粘土岩为主,是成熟陆块部分熔融作用的结果。微量元素标准化蛛网图、岩石组合R₁-R₂图解、Rb-Hf-Ta判别图、Rb-(Yb+Nb)和Rb-(Yb+Ta)图解均指示达尔应岩体是产生于同碰撞环境的花岗岩,它是冈玛错构造带在碰撞阶段过程中的岩浆岩记录。     

Triassic magmatism and Mo mineralization in Northeast China: geochronological and isotopic constraints from the Laojiagou porphyry Mo deposit

The Laojiagou Mo deposit is a newly discovered porphyry Mo deposit located in the Xilamulun Mo metallogenic belt, Northeast China. Mo mineralization mainly occurred within the monzogranite and monzogranite porphyry. Re–Os isochron dating of molybdenites indicate a mineralization age of 234.9 ± 3.1 Ma. Zircon LA–ICP–MS U–Pb analysis for monzogranite porphyry and monzogranite yield ²⁰⁶Pb/²³⁸U ages of 238.6 ± 1.8 and 241.3 ± 1.5 Ma, respectively, indicating that Laojiagou Mo mineralization is related to Middle Triassic magmatism. Hf isotopic compositions of zircons from both monzogranite porphyry and monzogranite are characterized by positive ε_Hf(t) values [ε_Hf(t) = 2.9–7.3 and 1.5–7.9, respectively] and young T_DM2 model ages, which implies that the magma was derived from juvenile crust created during accretion of the Central Asian Orogenic Belt (CAOB). Identification of the Laojiagou Mo deposit adds another important example of Triassic Mo mineralization in the Xilamulun Mo metallogenic belt where most Triassic Mo deposits in northeast China cluster around the northern margin of North China Craton. Based on the regional geological setting and geochronological and Hf isotope characteristics, we propose that Triassic Mo deposits and related magmatic rocks in northeast China formed during the last stages of evolution of the CAOB. These deposits formed during post-collisional extension after the closure of the Palaeo-Asian Ocean and amalgamation of the North China–Mongolian Block with the Siberian Craton.     

黑龙江张广才岭一面坡晚三叠世花岗岩地球化学特征和LA-ICP-MS锆石U-Pb年龄

对张广才岭南部一面坡花岗岩的地质学、岩石学、地球化学及锆石U-Pb年龄研究表明,岩石富硅富铝,属于过铝质岩石(A/CNK=1.04~1.07),全碱(K2O+Na2O)含量为8.24%~8.85%,K2O/Na2O值为1.58~1.68,属于高钾钙碱性系列I型花岗岩。岩石富集LREE、Rb、Th、U、K,相对亏损Nb、Ta、P、Ti,具有明显的Eu负异常,LA-ICP-MS锆石206Pb/238U年龄加权平均值为211Ma±4Ma(MSWD=1.4,2σ),代表了花岗岩的结晶年龄。岩石具有相对亏损的锆石Hf同位素组成(εHf(t)=+1.75~+13.81),TDM2为367~1136Ma。结合区域构造环境分析,认为一面坡晚三叠世花岗岩属于I型花岗岩,可能形成于后碰撞伸展构造环境,是岩石圈伸展阶段新增生下地壳物质发生部分熔融的产物。     

南祁连阳康地区花岗岩锆石年龄及地质意义

沿着南祁连北缘出露有一系列古生代的侵入岩,其形成时代一直存在争议,本文对出露在阳康地区的花岗岩进行了LA-ICP-MS锆石U-Pb年代学研究,确定了该地区花岗岩的时代归属;这些岩体主要分布在哈拉湖,阳康等地区,岩性主要为石英闪长岩、花岗闪长岩、二长花岗岩等,研究的结果表明其地质时代属晚奥陶世,对南祁连的大地构造演化具有重要的地质意义。     

黑龙江张广才岭一面坡晚三叠世花岗岩地球化学特征和LA-ICP-MS锆石U-Pb年龄

对张广才岭南部一面坡花岗岩的地质学、岩石学、地球化学及锆石U-Pb年龄研究表明,岩石富硅富铝,属于过铝质岩石（A/CNK=1.04~1.07）,全碱（K2O+Na2O）含量为8.24%~8.85%,K2O/Na2O值为1.58~1.68,属于高钾钙碱性系列I型花岗岩。岩石富集LREE、Rb、Th、U、K,相对亏损Nb、Ta、P、Ti,具有明显的Eu负异常,LA-ICP-MS锆石206Pb/238U年龄加权平均值为211Ma±4Ma（MSWD=1.4, 2σ）,代表了花岗岩的结晶年龄。岩石具有相对亏损的锆石Hf同位素组成（εHf(t)=+1.75～ +13.81）,TDM2为367~1136Ma。结合区域构造环境分析,认为一面坡晚三叠世花岗岩属于I型花岗岩,可能形成于后碰撞伸展构造环境,是岩石圈伸展阶段新增生下地壳物质发生部分熔融的产物。     

阿尔泰造山带北段晚三叠世早期岩浆作用成因及其对构造体制转换的制约

对阿尔泰造山带北段南缘出露的塔尔萨依岩体二云母正长花岗岩进行了LA-ICP-MS锆石U-Pb定年, 获得其 206Pb/238U年龄加权平均值为235±2 Ma(MSWD=0.46), 表明该花岗岩为晚三叠世早期岩浆活动的产物。全岩地球化学分析结果显示, 塔尔萨依岩体的二云母正长花岗岩和二云母二长花岗岩均具有高硅、高钾、低镁、低钛特征, 里特曼指数(σ)和铝饱和指数(A/CNK)分别大于2和1.1, 为高钾钙碱性强过铝质花岗岩。此外, 两类花岗岩均富集轻稀土元素和Rb、Th等微量元素, 亏损高场强元素Nb、Ta、Yb和Y。其低的Mg#值、Cr和Ni含量, 以及中等的CaO/Na2O和低的Al2O3/TiO2值, 表明研究区花岗岩形成于同碰撞构造环境。结合前人已有研究成果, 认为阿尔泰造山带三叠纪的构造体制转变在时空上存在差异, 整体表现出东—中段由挤压环境进入伸展构造背景的时间较北部早的趋势。     

特提斯喜马拉雅带中段东部三叠纪火山岩的地球化学和岩石成因

三叠纪火山岩分布于特提斯喜马拉雅带中段东部,古地理上位于大印度北东部.分别采用原子吸收分光度法、ICP-MS和全岩同位素稀释法对三叠纪火山岩的主量元素、微量元素和Sr-Nd同位素进行了分析,并用来研究其成分特征和成因.岩相学和地球化学指标显示三叠纪火山岩为玄武岩,MgO含量均很低（范围在4.27%～7.72%）,属于演化岩浆.早三叠世热马组和中三叠世桑康组具有较高的TiO2、TFeO和P2O5含量,稀土元素总量和轻重稀土元素的分馏程度均较高,Ti/V、Ti/Y、Zr/Y比值较高,富集高场强元素（如Nb、Zr等）,地球化学特征与峨眉山高Ti玄武岩相似,以更富集La、Ce、Zr、Hf等元素而有别于夏威夷碱性玄武岩,它们属大陆边缘裂谷背景的具有OIB型地球化学特征的碱性玄武岩;晚三叠世涅如组玄武岩以较低TiO2、TFeO和P2O5含量为特征,稀土元素总量和轻重稀土分馏程度均较低,高场强元素（如Nb、Zr等）丰度很低,为大陆边缘裂谷背景的具有E-MORB地球化学特征的拉斑玄武岩.三叠纪玄武岩Nd同位素组成随时间从轻度富集到亏损（εNd（t）=-1.2→-0.5→4.4）,指示岩浆源区具有从轻度富集到亏损的演化趋势.不相容元素（如La/Sm、La/Ta以及（Th/Ta）PM、（La/Nb）PM等）指示热马组和桑康组玄武岩遭受了一定程度下地壳混染,而涅如组没有遭受地壳混染.热马组和桑康组玄武岩还显示岩石圈地幔物质的印记,并与石榴石相二辉橄榄岩的低度部分熔融有关,而涅如组玄武岩除了具有E-MORB特征外,还与尖晶石相二辉橄榄岩的较高程度部分熔融有关.它们被解释为上涌的软流圈地幔物质与岩石圈地幔物质混合后在不同程度的拉张背景下发生减压熔融的产物.特提斯喜马拉雅带的三叠纪裂谷作用很可能具有主动裂谷作用的性质,较小规模的火山岩浆作用可用裂谷带之下上涌的地幔物质由于传导作用而变冷或正在孕育的地幔柱成因模式来解释.     

东天山黑石墩基性岩地球化学、锆石年代学、Sr-Nd-Hf同位素特征及其俯冲岩浆作用

在东天山康古尔塔格南黑石墩一带新发现一套基性岩,岩性以辉长岩和橄榄辉长岩为主,岩石具有相对较低SiO2(47.59％～50.79％)、富Na2O(2.72％～4.42％)贫K2O(0.26％～1.15％),低MgO(3.94％～12.55％),中等Mg#(47.6～66.64),高Al2O3(14.75％～19.65％...     

赣西北麦斜岩体锆石U-Pb年代学、地球化学以及Sr-Nd同位素研究及其岩石成因

赣西北麦斜岩体以灰白色中细粒等粒黑云母花岗闪长岩为主。本文通过锆石LA-ICP-MS法测得黑云母花岗闪长岩的侵位年龄为433.4±7.1Ma(MSWD=0.82)和431.8±6.0 Ma(MSWD=0.43),表明其属于早古生代岩浆活动的产物。岩石含少量角闪石,地球化学特征显示高硅(SiO_2=62.0%~71.43%)、高钾(K_2O/Na_2O=0.88~2.42)、富碱[(K_2O+Na_2O)=5.39%~8.12%]、低Fe_2O_3(2.61%~5.70%)、MgO(0.96%~2.90%)、CaO(1.39%~5.11%)、TiO_2(0.27%~0.67%)、P_2O_5(0.06%~0.10%)含量,整体弱过铝质(A/CNK介于0.98~1.25之间,平均为1.08)特征,且P_2O_5含量与SiO_2含量呈明显的负相关关系,矿物学和地球化学特征显示其属于高钾钙碱性Ⅰ型花岗岩。微量元素特征上表现为富集Rb、Th、Pb和LREE,亏损Nb、Ta、Ti、P、Ba、Sr等元素,轻重稀土分馏明显[(La/Yb)_N=5.00~40.42,平均为17.17],弱到中等Eu负异常(δEu=0.63~1.00,平均为0.77)。岩石具有均一的Sr-Nd同位素组成[(~(87)Sr/~(86)Sr)_i=0.708444~0.708962,ε_(Nd)(t)=-7.48~-7.22,t_(2DM)(Nd)=1.75~1.87Ga,平均为1.81Ga],相对较高的(~(87)Sr/~(86)Sr)_i比值和低ε_(Nd)(t)值及较古老Nd模式年龄暗示其来自以古元古代地壳为主要成分的部分熔融作用产物。综合实验岩石学以及样品地球化学特征,表明麦斜黑云母花岗闪长岩形成于中、下地壳中-基性岩(如角闪岩)的水不饱和部分熔融,初始岩浆中可能有一定量的幔源物质混入,并经历了广泛的角闪石、黑云母、钛铁矿、榍石、斜长石、磷灰石等矿物的分离结晶作用,这些幔源物质是华南古元古代时期经历了俯冲流体的交代作用而形成富集地幔的部分熔融产物。结合区域地质背景以及岩石地球化学特征认为其可能形成于陆内后碰撞环境,由幔源基性物质底侵,导致华南早古生代中下地壳部分熔融而形成广泛分布的华南早古生代陆内岩浆岩。