新疆富蕴可可托海—二台断裂带中假玄武玻璃及其围岩的年代学研究

发育在新疆富蕴可可托海—二台断裂带中的假玄武玻璃是古地震断裂快速滑移形成的构造岩。地质产状、显微构造研究表明,这些假玄武玻璃主要由发生重结晶的玻璃质熔融体形成。假玄武玻璃基质的全岩40Ar/39Ar阶段升温方法主阶段和KAr年龄分别为282.8±3.8 Ma和276.4±7.4 Ma。假玄武玻璃所在母岩（黑云母花岗岩和钾长花岗岩）的锆石U-Pb年龄分别为390.4±1.0 Ma和396.3±0.1 Ma,表明二台断裂带中的假玄武玻璃是在二叠世早期形成的,也说明二台断裂带古地震活动至少可以追溯到晚古生代（早二叠世早期）。尽管二台断裂带是现今仍然活动的地震构造带,但目前所见到的假玄武玻璃是早二叠世时期古地震活动的产物。1931年的富蕴80级地震仅仅是沿着二台断裂带发生的多次构造活动的一次活动,与假玄武玻璃之间没有成因上的联系。     

大别造山带东部假玄武玻璃的成因

最近,在大别造山带东部广泛发现了假玄武玻璃出露点,这些假玄武玻璃主要沿NE-SW向断裂带或剪切带发育。某些假玄武玻璃内发育糜棱质条带。本文主要讨论了大别造山带东部假玄武玻璃的显微构造、岩石化学及稀土元素地球化学等特征,在此基础上阐述了发育在该地区的假玄武玻璃的成因。      

大别造山带东部假玄武玻璃的显微构造特征及其意义

最近,在大别造山带东部发现了广泛的地震成因假玄武玻璃,这些假玄武玻璃主要呈简单脉状沿NE-SW向走滑断裂带或剪切带发育,后者大多与郯庐断裂带平行并穿切了包括白垩纪花岗岩在内的地质体。某些假玄武玻璃内发育由暗色石英条纹构成的糜棱质条带。本文通过普通光学显微镜和扫描电镜观察分析,详细研究对比了不同断裂带内部发育的假玄武玻璃及其围岩在显微构造特征上的差异及联系。根据岩石的组构特征,证实所发现的这些假玄武玻璃主要是由母岩的超碎裂岩化形成的,但在点1发育的假玄武玻璃基质的扫描电镜影象特征上,沿某些残斑矿物(钾长石、斜长石、黄铁矿)的边缘可以看到些许代表摩擦熔融成因的熔蚀状港湾结构,说明假玄武玻璃形成过程中曾经发生了程度较低的局部熔融作用。肉眼所见到的糜棱质石英条纹在显微镜下证实为早期的糜棱面理。同时,岩石组构的叠加显示,含假玄武玻璃的断裂带及假玄武玻璃本身普遍具有多期性,且晚期构造产物(或假玄武玻璃)总是较早期产物(或假玄武玻璃)碎裂岩化作用更加强烈,说明先期存在的构造软化带在控制假玄武玻璃形成过程中起着非常重要的作用,即构造带抬升过程中伴随的多期构造及细粒化是形成假玄武玻璃的基础。岩石的变形序列总体上显示为韧性-韧脆性-脆性的演化过程,从而证实了这些假玄武玻璃总体上形成于造山带抬升过程,而不是早期的俯冲过程。     

广东河台金矿假玄武玻璃地球化学和年代学特征及其地质意义

前人对河台金矿中的假玄武玻璃早有报道,但是因为未认识到其与成矿的关系而被忽视。在前人发现的糜棱岩中假玄武玻璃的基础上,本次研究又发现了三种其他岩性中的假玄武玻璃。河台金矿中的假玄武玻璃呈黑色脉状、网脉状和树枝状贯穿于糜棱岩化片岩、糜棱岩、混合岩和矿体中。本研究结合野外宏观特征和室内的岩相学微观特征,运用粉晶X射线衍射、全岩地球化学和Ar-Ar同位素等实验分析手段,比较了河台金矿不同地质体中假玄武玻璃岩脉的特征。研究发现假玄武玻璃脉体中存在树枝状微晶结构和碎屑颗粒的港湾结构,同时也含有碎裂成因的石英、长石,表明其成因以同震断层的摩擦熔融为主,并伴随有少量碎裂化。通过计算得出假玄武玻璃样品中结晶态的各类矿物含量为石英53.3%、伊利石20.5%、高岭石17.3%、钾长石8.9%。假玄武玻璃与围岩都具有富SiO_2和Al_2O_3,富K_2O贫Na_2O,低MgO和Fe_2O_3~T的地球化学特征。两者的稀土元素配分型式也非常相似,都显示轻稀土富集和中等程度的负Eu异常(δEu=0.51～0.71)。假玄武玻璃的显微构造和地球化学特征指示其主要是由围岩原地熔融形成的,形成深度在6～18 km。我们认为河台金矿的假玄武玻璃可以指示云开大山抬升过程中伴随着地震的发生,同时,假玄武玻璃脉体在空间上切穿矿体,因此假玄武玻璃的⁴⁰Ar/³⁹Ar年龄123.3±1.0 Ma可以作为河台金矿的成矿年龄上限。     

Pseudotachylite from the Main Zone of the Hidaka metamorphic belt, Hokkaido, northern Japan

Pseudotachylite veins have been found in the mylonite zone of the Hidaka metamorphic belt, Hokkaido, northern Japan. They are associated with faults with WNW-ESE to ENE-WSW or NE-SW trends which make a conjugate set, cutting foliations of the host mylonitic rocks with high obliquity. The mylonitic rocks comprise greenschist facies to prehnite-pumpellyite facies mineral assemblages. The mode of occurrence of the pseudotachylite veins indicates that they were generated on surfaces of the faults and were intruded as injection veins along microfractures in the host rocks during brittle deformation in near-surface environments. An analysis of the deformational and metamorphic history of the Hidaka Main Zone suggests that the ambient rock temperature was 200–300° C immediately before the formation of the Hidaka pseudotachylite. Three textural types of veins are distinguished: cryptocrystalline, microcrystalline and glassy. The cryptocrystalline or glassy type often occupies the marginal zones of the microcrystalline-type veins. The microcrystalline type is largely made up of quench microlites of orthopyroxene, clinopyroxene, biotite, plagioclase and opaque minerals with small amounts of amphibole microlites. The interstices of these microlites are occupied by glassy and/or cryptocrystalline materials. The presence of microlites and glasses in the pseudotachylite veins suggests that the pseudotachylites are the products of rapid cooling of silicate melts at depths of less than 5 km. The bulk chemical composition of the pseudotachylite veins is characterized by low SiO₂ and a high water content and is very close to that of the host mylonitic rocks. This indicates that the pseudotachylite was formed by virtual total melting of the host rocks with sufficient hydrous mineral phases. Local chemical variation in the glassy parts of the pseudotachylite veins may be due to either crystallization of quench microlites or the disequilibrium nature of melting of mineral fragments and incomplete mixing of the melts. Pyroxene microlites show a crystallization trend from hypersthene through pigeonite to subcalcic augite with unusually high Al contents. The presence of pigeonite and high-Al pyroxene microlites, of hornblende and biotite microlites and rare plagioclase microlites may indicate the high temperature and high water content of the melt which formed the pseudotachylite veins. The melt temperatures were estimated to be up to 1100° C using a two-pyroxene geothermometer. Using published data relating water solubilities in high-temperature andesitic magmas to pressure, a depth estimate of about 4 km is inferred for the Hidaka pseudotachylites. Evidence derived from pseudotachylites in the Hidaka metamorphic belt supports the conclusion that pseudotachylite is formed by frictional melting along fault surfaces at shallow depths from rocks containing hydrous minerals.     

The Liaonan Metamorphic Core Complex： Constitution, Structure and Evolution

The Liaonan metamorphic core complex (mcc) has a three-layer structure and is constituted by five parts, i.e. a detachment fault zone, an allochthonous upper plate and an supradetachment basin above the fault zone, and highly metamorphosed rocks and intrusive rocks in the lower plate. The allochthonous upper plate is mainly of Neoproterozoic and Paleozoic rocks weakly deformed and metamorphosed in pre-Indosinan stage. Above these rocks is a small-scale supradetachment basin of Cretaceous sedimentary and volcanic rocks. The lower plate is dominated by Archean TTG gneisses with minor amount of supracrustal rocks. The Archean rocks are intruded by late Mesozoic synkinematic monzogranitic and granitic plutons. Different types of fault rocks, providing clues to the evolution of the detachment fault zone, are well-preserved in the fault zone, e.g. mylonitic gneiss, mylonites, brecciated mylonites, microbreccias and pseudotachylites. Lineations in lower plate granitic intrusions have consistent orientation that indicate uniform top-to-NW shearing along the main detachment fault zone. This also provides evidence for the synkinematic characteristics of the granitic plutons in the lower plate. Structural analysis of the different parts in the mcc and isotopic dating of plutonic rocks from the lower plate and mylonitic rocks from detachment fault zone suggest that exhumation of the mcc started with regional crustal extension due to crustal block rotation and tangential shearing. The extension triggered magma formation, upwelling and emplacement. This event ended with appearance of pseudotachylite and fault gauges formed at the uppermost crustal level. U-Pb dating of single zircon grains from granitic rocks in the lower plate gives an age of 130±5 Ma, and biotite grains from the mam detachment fault zone have 40Ar-39Ar ages of 108-119 Ma. Several aspects may provide constraints for the exhumation of the Liaonan mcc. These include regional extensional setting, cover/basement contact, temporal and spatial coupling of extension and magmatism, basin development and evolution of fault tectonites along detachment fault zone. We propose that the exhumation of the Liaonan mcc resulted from regional extension and thinning of crust or lithosphere in eastern North China, and accompanied with synkinematic intrusion of granitic plutons, formation of detachment fault zone, uplifting and exhumation of lower-plate rocks, and appearance of supradetachment basin.     

Tectonic Significance of Fissure Veins Associated with Pseudotachylites of the Kui-Chitraseni Shear Zone, Aravalli Mountain, NW India

Kui-Chitraseni Shear Zone of the Precambrian Aravalli Mountain, NW India is marked by a nearly 400 m-wide NE-SW trending belt of cataclasites developed on the granites and metasediments of the Delhi Supergroup. The cataclasites are criss crossed by pseudotachylite and fissure-veins. While the pseudotachylites are aphanitic to microlitic, the fissure veins are characterized by syntaxial-bitaxial as well as unitaxial growth of elongate quartz grains. Textural study of the fissure veins suggests crystallization of quartz grains in a dilational environment in hydrous condition. Contrarily the pseudotachylites bear the evidence of frictional melting of rocks under anhydrous conditions. Since in many instances it is observed that the fissure veins have replaced the pseudotachylites following the crack seal mechanism, the formation of fissure veins is considered to be latekinematic to pseudotachylites. Hence it is interpreted that the pseudotachylites and fissure veins were formed in two distinct tectonic events. While pseudotachylites were formed in a compressional setting resulted from thrusting along the shear zone, the fissure veins have been formed in an extensional setting during a late stage normal faulting. In light of this tectonic rejuvenation along the Kui-Chitraseni Shear Zone, various lineaments present within the Aravalli Mountains need further study for understanding the evolution of the region.     

东南极哈姆峰地区假玄武玻璃的显微构造、年代学及其地质意义

发育在东南极普里兹湾西南部哈姆峰地区麻粒岩相花岗质片麻岩中的假玄武玻璃沿着近东西向断裂带分布。显微构造特征表明,该地假玄武玻璃基质中普遍发育球粒结构及树枝状、放射状-针状等不同形状及组合的矿物微晶体,说明这些假玄武玻璃是地震断层快速滑移过程中摩擦熔融作用的产物。假玄武玻璃中的微晶体矿物组合大体分为两种,它们分布在构造带不同地段:一种是以"紫苏辉石+斜长石"组合为主,分布于构造带东北部地段;一种是以"黑云母+斜长石+钾长石+石英"的组合为主,分布于构造带西南部地段,说明沿构造带不同部位构造环境及应力分布的不均匀性。同时,微晶体中富铝紫苏辉石的存在,表明假玄武玻璃形成过程及其后期的结晶过程可能处于高温(麻粒岩相)的构造环境下。假玄武玻璃的基质全岩K-Ar年龄为878.1±16.8 Ma,全岩40Ar/39Ar年龄谱系中所记录的年龄值主要集中在925~626 Ma。结合区域对比看,假玄武玻璃应该形成于格林维尔期构造事件。      

Pseudotachylite associated with a bedding-parallel fault zone between the Witwatersrand and Ventersdorp Supergroups,South Africa

A Proterozoic bedding-parallel fault zone is described from the Witwatersrand basin in South Africa. The fault zone is dominated by pseudotachylite, the youngest tectonite present, but also contains quartz veins and cataclasites which post-date the spatially associated mylonites. Both tectonic eliminations and duplications are caused by the fault zone which is dominated by a northerly to westerly overthrusting. The fault rocks probably did not form during a single event but as a result of a minimum of two periods of activation of the fault zone separated in time by at least the period required to deposit in excess of 4 km of sediments belonging to the lower part of the Transvaal Sequence. Equivocal evidence suggests that the pseudotachylites, which probably formed as a result of frictional fusion on fault planes, may have formed at similar depths to the mylonites. Consequently the related parameters of pressure and temperature are not considered to be as important in determining whether brittle or ductile deformation occurs, as are pore fluid pressure and strain rate. The age, direction of tectonic transport and a characteristic enrichment in lead all suggest that there may be a genetic link between the pseudotachylites in this fault zone and the type pseudotachylites at Vredefort, 60 km to the south.     

An Ar–Ar laser-probe study of pseudotachylites in charnockite gneisses from the Cauvery Shear Zone system, South India

The age of pseudotachylite formation in the crustal-scale Cauvery Shear Zone system of the Precambrian Southern Granulite Terrain (South India) has been analyzed by laser-probe ⁴⁰Ar–³⁹Ar dating. Laser spot analyses from a pseudotachylite from the Salem–Attur shear zone have yielded ages ranging from 1214 to 904 Ma. Some evidence for the presence of excess Ar is indicated by the scatter of ages from this locality. The host gneiss preserves Palaeoproterozoic Rb–Sr whole rock–biotite ages (2350 ± 11 to 2241 ± 11 Ma). A mylonite in the Koorg shear, ca. 200 km to the north, yielded an age of 895 ± 17 Ma the consistency of the age distribution from spot analyses precludes the presence of significant excess Ar. Despite published evidence for the growth of high-grade minerals within some components of the Cauvery Shear Zone during the Pan-African event (700–550 Ma), the pseudotachylites in this study provide no evidence for Pan-African formation. Instead they document the first evidence for Mesoproterozoic tectonism in the Cauvery Shear Zone system, thus prompting a review of the correlation between the Cauvery Shear Zone system and the large-scale shear zones located elsewhere in eastern Gondwana.     

40Ar/39Ar dating constraints on the high-angle normal faulting along the southern segment of the Tan-Lu fault system: An implication for the onset of eastern China rift-systems

High-angle normal faulting in eastern China was an important tectonic process responsible for the rifting of the eastern Asian continental margin. Along the southern segment of the Tan-Lu fault system, part of the eastern China rift-system, 55–70° east-dipping normal faults are the oldest structures within this rift-system. Chlorite, pseudotachylite, and fault breccia are found in fault zones, which are characterized by microstructures and syn-deformation chlorite minerals aligned parallel to a down-dip stretching lineation. ⁴⁰Ar/³⁹Ar dating of syn-deformation chlorite and K-feldspar from the fault gouge zone yields cooling ages of ～75–70 Ma, interpreted as the timing of slip along the normal faults. This age is older than that of opening of the Japanese sea and back-arc extension in the west Pacific, but similar to the onset of the Indo-Asian (soft?) collision.     

假玄武玻璃的研究进展与现状

在国外有关假玄武玻璃（pseudotachylite)的研究已经有百余年的历史,在野外产状、显微镜观察和实验模拟等方面积累了丰富的资料。而国内在这方面的研究甚少。近年来,随着人们对“活断层”研究的深入,所谓有“地震化石”之称的假玄武玻璃也日益为研究者们所重视。假玄武玻璃通常认为是与地震断层有关的高应变速率条件下的产物。假玄武玻璃的研究对了解地震时地下深处断层带的变形机制等多方面具有重要意义。尤其是通过模拟假玄武玻璃形成时的相似条件（主要是力学机制和化学机制）,可以了解假玄武玻璃形成时断层剪切带变形历史。为了使国内对这一研究领域感兴趣的学者了解假玄武玻璃的形成过程及其所反映的意义,本文从假玄武玻璃的地质特征及成因等几个方面进行了总结,以飧读者。     

内蒙古呼和浩特变质核杂岩韧性拆离带40Ar-39Ar定年及其构造含义

晚中生代,内蒙古大青山依次经历晚侏罗世盘羊山逆冲推覆、早白垩世呼和浩特变质核杂岩伸展、早白垩世大青山逆冲推覆断层及早白垩世以来高角度正断层复杂构造演化。其中,呼和浩特变质核杂岩韧性剪切带的冷却时间和抬升机制的制约尚不明确。本文在野外考察和显微构造分析基础上,采用逐步加热40Ar-39Ar定年法对韧性剪切带内不同单矿物的冷却年龄进行了测定。角闪石、白云母、黑云母和钾长石单矿物40Ar-39Ar冷却年龄处于120~116Ma之间。结合已有年龄数据及单矿物封闭温度,构建了韧性剪切带的冷却曲线。结果表明,韧性剪切带在122~115Ma期间存在一个明显的快速冷却过程。这一阶段快速冷却是与变质核杂岩拆离断层相关核部杂岩拆离折返作为大青山逆冲推覆断层上盘抬升的结果。     

Mineralization Ages of Gold-Hydrothermal Deposits in Northern Zone of Eastern Kunlun Mountains based on Fission Track Analysis

MINERALIZATION AGES OF GOLD-HYDROTHERMAL DEPOSITS IN NORTHERN ZONE OF EASTERN KUNLUN MOUNTAINS BASED ON FISSION TRACK ANALYSIStheOpenLaboratoryofNuclearAnalysisTechniques;;ChineseAcademyofSciences     

Thermal Evolution of the Tanlu Fault Zone on the Eastern Margin of the Dabie Mountains and Its Tectonic Implications

Five samples of muscovite from mylonites of the earlier Tanlu ductile shear zone on the eastern margin of the Dabie Mountains yield 40Ar/39Ar ages ranging from 178 Ma to 196 Ma. Three of them have reliable plateau ages of 188.7±0.7 Ma, 189.7±0.6 Ma and 192.5±0.7 Ma respectively, which indicates a syn-orogenic, sinistral strike-slip thermal event. This displacement movement derived from the continent-continent collision of the North and South China blocks took place in the Early Jurassic and after uplifting of high-pressure to ultrahigh-pressure slabs to the mid-crust. It is suggested that during the collision the Tanlu fault zone was an intracontinental transform fault caused by differential subduction speeds. The 40Ar/39Ar ages of mylonite whole-rock and muscovite from the later Tanlu ductile shear zone suggest another sinistral strike-slip cooling event at 128 Ma. During this strike-slip faulting, large-scale intrusion and doming uplift occurred in the eastern part of the Dabie orogenic belt. Data o     

大别山超高压变质带中“脉状”榴辉岩的锆石U-Pb年龄

榴辉岩广泛分布于大别山超高压变质带中,出露规模大小不等,成因类型复杂,围岩类型多样,不仅产于基性、超基性岩中,还产于片麻岩、大理岩、石英硬玉岩、变质花岗岩中。对大别山超高压变质带出露的两处"脉状"榴辉岩进行锆石U Pb年龄测定,分别获得上交点年龄(858±25)Ma和(845±150)Ma,下交点年龄(249±20)Ma和(237±13)Ma,表明其原岩形成时代为新元古代,印支期发生过高压—超高压变质作用,与大别山超高压变质带中其他类型的榴辉岩年龄基本一致。     

Timing of deformation phases within the South Finland shear zone, SW Finland

The Palaeoproterozoic Svecofennian crust in southern and central Fennoscandia was established about 1.8 Ga ago after a prolonged history of accretion and intrusion. During late stages of the Svecofennian orogeny, deformation was partitioned into several crustal-scale shear zones in present-day Finland, Sweden and Estonia. One such major ductile deformation zone, ‘the South Finland shear zone’ (SFSZ) extends for almost 200 km through the Åland archipelago in southwestern Finland, and further along the southern and southwestern coast of Finland. This more than a kilometer wide transpressional zone appears to have been repeatedly reactivated. The deformation started with a period of regional, ductile dextral shearing of igneous rocks, producing striped granodioritic and tonalitic gneisses. The ductile phases are locally overprinted and followed by ductile to semi-ductile deformation evidenced by mylonite zones of variable width. The last stage of tectonic activity along the shear zone is recorded by pseudotachylites. Within this study, we dated zircons (SIMS U–Pb) and titanites (ID-TIMS U–Pb) from eight rock samples, and two pseudotachylite whole-rock samples (⁴⁰Ar/³⁹Ar) in order to reconstruct the deformation and (re)activation history of the shear zone.The results suggest that the medium-grained gneisses underwent three distinct deformation phases separated by time intervals without regional deformation. The ductile deformation within the study area initiated at 1.85 Ga. A second, more intensive deformation phase existed around 1.83 Ga, by which the shear zone was already well developed. Finally, the last ductile event is recorded by 1.79 Ga metamorphic titanites in relatively granoblastic granitoid gneisses that nevertheless already display protomylonitic textures, suggesting the initiation of large-scale mylonitisation around or soon after this time. The age of a pseudotachylite sample and, hence, the brittle deformation is bracketed between 1.78 and 1.58 Ga based on the age of pegmatites cut by pseudotachylites as well as ⁴⁰Ar/³⁹Ar minimum ages for the pseudotachylite, respectively. The data imply that the rocks within the study area entered the ductile–brittle transition zone due to rapid cooling and exhumation of the crust after 1.79 Ga.     

~(40)/Ar~(39)Ar Ages of Auriferous Quartz Veins from the Fengyang and Zhangbaling Regions and Their Geological Significance

1IntroductionAuriferousquartzveinsarecommonintheFengyangandZhangbalingregionsofAnhuiProvinceandtheyconstitutetheRongdu ,Zhuding ,Dagongshan ,MaoshanandShangchenggolddepositsandalotofgoldperspectives .TheRb SrisochronagesofalterationmineralsfromtheRongduandDagongshangolddepositsare (10 9.0± 4 .4 )Maand (15 3.76± 11.2 )Ma ,respectively (Dongetal .,1995 ) .Thereisalargedifferenceinagebetweenthetwogolddeposits ,butitcanbeseenthatthegolddepositswereformedinLateJurassictoEarlyCretaceous .A…     

华南腹地白垩纪A型花岗岩类或碱性侵入岩年代学及其对华南晚中生代构造演化的制约

华南腹地存在多个白垩纪的A型花岗岩类或碱性侵入岩,如安徽花山霓辉石钠闪石花岗岩、福建大沅村霓辉石钠铁闪石花岗岩、广东恶鸡脑霞石方钠石正长岩以及浙江大和山辉石石英正长斑岩、苏村晶洞钾长花岗岩。锆石SHRIMP和矿物的40Ar-39Ar年代学研究表明,这些岩石主要形成于137-86Ma。以本文的年代学研究为基础,并结合前人大量研究成果, 将华南晚中生代的A型花岗岩类或碱性侵入岩大致分成三期:(1)侏罗纪(184-152Ma)A型花岗岩类或碱性侵入岩,主要沿“十-杭裂谷带”南段分布,在赣南也有分布,可能与古太平洋板块低速斜向俯冲或平移所导致的走滑伸展或与不受古太平洋板块运动影响的岩石圈伸展有关;(2)早白垩世(139-123Ma)A型花岗岩类或碱性侵入岩,分布于政和-大埔断裂带以西,可能与古太平洋板块快速斜向俯冲所导致的弧后伸展或岩石圈减薄有关;(3)晚白垩世(101-86Ma)A型花岗岩类或碱性侵入岩,主要沿闽浙沿海地区分布,同时在华南腹地也有零星分布,可能与大陆边缘弧的塌陷(collapse)或俯冲洋壳反转(roll- back)后的岩石圈伸展有关。     

钦-杭成矿带南段庞西垌断裂带热年代学证据

庞西垌断裂带是钦-杭成矿带南段众多NE向韧性剪切带的其中一条,控制着一系列韧性剪切带型银金矿床的分布.对其进行热年代学研究有助于了解钦-杭成矿带南段NE向韧性剪切带的构造演化及其对伴生矿床的控制作用.获得的庞西垌断裂带内糜棱岩中两件白云母40Ar/39Ar总气体年龄分别为221.98±1.16 Ma和223.77±1.16 Ma.据此认为庞西垌断裂带在印支期发生韧性剪切活动,为伴生矿床的形成提供了有利空间;在同一糜棱岩样品中获得的磷灰石、锆石裂变径迹年龄分别为64.83±4.13 Ma和75.69±2.88 Ma,结合热史模拟结果可以得出,庞西垌断裂带在75~60 Ma期间发生了快速冷却作用（6.2 ℃/Ma）,与区域整体缓慢冷却过程（1.5 ℃/Ma）差别显著,据此推测庞西垌断裂带可能在约75~60 Ma期间再次发生活动,而庞西垌银金矿床可能形成于晚白垩世.