巴楚辉绿岩墙的岩石成因及其对塔里木大火成岩省岩浆演化的启示

早二叠世塔里木大火成岩省主要有两期岩浆活动:以柯坪玄武岩为代表的喷出岩形成较早(~290Ma),以巴楚超基性-基性-长英质侵入体和岩墙为代表的侵入岩形成较晚(~280Ma)。本研究选取代表晚期岩浆活动的巴楚辉绿岩墙为研究对象,旨在为认识塔里木地幔柱活动及与岩石圈的相互作用提供更多信息。巴楚辉绿岩XHZ-10样品中的锆石均为继承性锆石,不能用来限定其侵位时代。然而,野外关系表明巴楚辉绿岩墙属于塔里木大火成岩省的第二期岩浆活动。巴楚辉绿岩墙经历了橄榄石、辉石和磁铁矿的分离结晶。Nd同位素比值与SiO₂和La/Nb比值的相关性以及继承性锆石年龄(2480~717Ma,主要集中在~800Ma)表明,新元古代基底的同化混染作用可以解释其ε_Nd具有较大的变化范围(-2.6~+5.1)。受混染程度最小的样品具有与洋岛玄武岩(OIB)极其相似的微量元素特征,并且具有亏损的Nd同位素组成(ε_Nd=~+5),暗示其来源于富集的对流地幔源区,与早期(~290Ma)具有岩石圈地幔源区特征的玄武岩形成鲜明对比。本文提出地幔柱侧向流动模型以解释两期岩浆的时空分布和地球化学差异:当地幔柱上升至塔里木岩石圈底部时,巨厚的岩石圈地幔(>140km)会阻碍其减压熔融;但不断积累在岩石圈底部的地幔柱物质提供足够的热,促使早期富集交代的岩石圈地幔发生部分熔融,形成~290Ma的玄武岩;地幔柱物质将向岩石圈厚度较薄的边缘地区侧向流动,发生减压熔融,形成的熔体侵位到地壳中形成超基性-基性-长英质侵入岩和辉绿岩墙,并诱发地壳的熔融形成长英质火山岩。     

塔里木大火成岩省瓦吉里塔格霞石岩稀有气体同位素特征及其地质意义

稀有气体被广泛用作地球化学示踪剂,本文对塔里木大火成岩省西北缘瓦吉里塔格霞石岩中的橄榄石和辉石单矿物进行了稀有气体同位素测定。结果表明,瓦吉里塔格霞石岩中的橄榄石和辉石单矿物具有较低的~3He/~4He值(分别为2.0~2.4 Ra和0.65~0.85 Ra)和略高于大气值的~(40)Ar/~(36)Ar值(342.3~651.7),反映了由古板块俯冲导致的较低的He、Ar同位素比值特征。研究表明,早中古生代南天山洋向南俯冲到塔里木板块之下,将富U或富~4He以及含有大气组分的流体带入到深部地幔,在塔里木地幔柱的作用下地幔源区发生低程度部分熔融产生霞石岩岩浆。     

塔里木地台西南缘皮山煌斑岩的^40Ar／^39Ar年龄及其地质意义

塔里木地台西南缘皮山县煌斑岩脉群为超钾系列的煌斑岩,侵位于元古宇角门片岩中。经~(40)Ar/~(39)Ar法测定,煌斑岩中金云母的等时线年龄为(231.7±0.3)Ma,全岩等时线年龄为(228.5±0.3)Ma。地球化学数据指示其源区为受俯冲     

试论大火成岩省与成矿作用

根据组成大火成岩省的岩浆类型不同,大火成岩省可以分为两类,一是以基性火成岩为主的镁铁质大火成岩省（MLIPs）,二是以酸性火成岩为主的长英质大火成岩省（SLIPs）。它们都是由于在异常高的地幔热流参与下导致地幔或地壳大规模熔融形成的。大火成岩省独特的巨量岩浆活动是引起多层次物质和能量交换的重要场 所。成矿物质的聚集导致成矿作用和矿床的形成是必然的,因此大火成岩省本身就是一个大成矿系统。在这个成矿系统中,由于物源、成分、温度、压力、流体和氧逸度等条件的差异性,形成不同种类的矿化和矿床,并构成一定的成矿系列。镁铁质大火成岩省中形成的矿床类型有岩浆硫化物型Cr-Cu-Ni-PGE矿床和Ti-Fe 氧化物型V-Ti-Fe 矿床,热液型的Cu-Pb-Zn-Au-Ag矿床,以及远程低温热液矿床等。长英质大火成岩省形成的矿床类型为岩浆和交代型、热液型Cu-Pb-Zn-Au-Ag,W-Sn,U-Th-REE矿床,以及Sb-As矿床等。加强对大火成岩省及其成矿机理的研究,有望形成新的成矿理论和加速超大型矿床的发现。     

中国东部中生代大规模岩浆活动与长英质大火成岩省问题

笔者认为,中国东部中生代大规模岩浆活动很难用太平洋板块的俯冲来解释,中国东部中生代大规模岩浆活动可能相当于几个不同时期发育的长英质大火成岩省,与中生代东亚超级地幔柱的活动有关.世界上存在两类大火成岩省,一类以镁铁质岩为主(M-LIP);另一类以长英质岩为主(F-LIP).中国也存在上述两类大火成岩省,二叠纪的峨眉山玄武岩属于前者,中国东部中生代大规模的岩浆活动属于后者.二者可能均与地幔柱的活动有关,不同在于镁铁质大火成岩省的地幔柱上升停滞在岩石圈底部,在那里发生部分熔融形成大规模玄武岩喷发;而与长英质大火成岩省有关的地幔柱可抵达下地壳底部直接烘烤和加热下地壳,形成长英质成分的岩浆岩.学术界通常认为中国东部中生代大规模岩浆活动与太平洋板块向西俯冲导致的软流圈地幔上升有关,本文却认为它可能与来自下地幔的地幔柱有关.大火成岩省矿产丰富,与镁铁质大火成岩省有关的矿产有铜、镍、铬、铂、钯等,与长英质大火成岩省有关的矿产有金、铜、钨、锡、钼、铋、锑、铀等.     

普朗斑岩铜矿岩浆混合作用：岩石学及元素地球化学证据

普朗斑岩铜矿花岗闪长斑岩中存在大量的随机分布的镁铁质微粒包体,包体与寄主岩存在渐变接触关系。包体成分为闪长质,具有岩浆结构,存在针状磷灰石,显示了快速冷却结晶的特征。包体内可见具有暗色矿物镶边的眼球状石英,表明存在岩浆混合作用。寄主岩岩体规模较小,呈岩枝状产出,包体和寄主岩均为似斑状结构,说明两种岩浆侵位和发生岩浆混合作用的深度较浅。元素地球化学特征显示包体与寄主岩的之间有成分交换。包体和寄主岩强不相容元素均富集,高场强元素Nb、Ta、Ti均表现出显著的负异常,具有典型的岛弧岩浆岩的微量元素特征,包体和寄主岩Mg＃较高,在同等Si条件下比玄武岩部分熔融体富K2O和MgO,意味着源区必须有幔源岩浆的贡献。普朗斑岩铜矿蚀变矿化模式反映了其成矿环境偏基性,暗示镁铁质岩浆的加入对成矿具有贡献。     

大火成岩省的成矿效应

大火成岩省(LIPs)是地质历史上重大的地质事件,巨量的岩浆堆积形成了丰富的矿产资源.按照成矿作用与LIPs事件的关系,将其划分为两种类型:①成矿作用与LIPs事件直接相关,两者时间一致或者成矿作用稍晚,该类型矿床可以作为LIPs的组成部分;②成矿作用与LIPs事件在时间上有明显的间断,但与LIPs有间接的成因联系.与...     

塔里木和中亚造山带西段二叠纪大火成岩省的两类地幔源区

对塔里木和中亚造山带西段二叠纪玄武质岩石地质、年龄、元素地球化学、同位素组成的系统总结表明,二叠纪火成岩在分布面积、岩石类型(以玄武岩占绝对优势)、活动时间(以275Ma左右为峰期)等方面均与世界典型的大火成岩省一致,将其命名为巴楚大火成岩省(Bachu LIP)。元素和同位素地球化学特征表明,塔里木玄武岩来自长期富集的岩石圈地幔,来源深度为60~80km。塔里木基性岩墙和超镁铁-镁铁杂岩的原始岩浆可能来自软流圈地幔(OIB)部分熔融。中亚造山带西段的玄武岩、基性岩墙和超镁铁-镁铁杂岩主要来自被俯冲带熔体交代的强烈亏损的岩石圈地幔,其中部分地区可能有软流圈物质的加入,如东天山和阿勒泰南缘高Ti系列的玄武质岩石。根据元素和同位素地球化学资料,将巴楚大火成岩省分为2个地幔省(mantle domain),即塔里木省和中亚省。这2个不同地幔省的成矿系列也有显著的差异,塔里木省为钒-钛磁铁矿矿床,而中亚则以铜-镍-(铂族金属)硫化物矿床为主,成矿作用的差异和岩浆地幔源区的差异是完全对应的。综合地质、地球化学和成矿作用,认为巴楚大火成岩省的形成和二叠纪地幔柱密切相关。     

塔里木大火成岩省熔结凝灰岩中富磷-稀土矿物集合体的识别及其意义

高分异的高硅流纹岩具有稀土元素(REE)成矿的潜在价值.塔里木大火成岩省以发育高比例的长英质岩石为特征,但其是否具有稀土成矿的潜力还缺少有力证据.本次研究以来自塔里木大火成岩省塔北隆起S42井的高硅熔结凝灰岩为研究对象,从中识别出多种富Fe-P-REE的矿物集合体:①熔结凝灰岩的岩屑具有由磁铁矿、独居石和碱性长石等矿物...     

塔里木和中亚造山带西段二叠纪大火成岩省的两类地幔源区

对塔里木和中亚造山带西段二叠纪玄武质岩石地质、年龄、元素地球化学、同位素组成的系统总结表明,二叠纪火成岩在分布面积、岩石类型(以玄武岩占绝对优势)、活动时间(以275Ma左右为峰期)等方面均与世界典型的大火成岩省一致,将其命名为巴楚大火成岩省(Bachu LIP)。元素和同位素地球化学特征表明,塔里木玄武岩来自长期富集的岩石圈地幔,来源深度为60～80km。塔里木基性岩墙和超镁铁-镁铁杂岩的原始岩浆可能来自软流圈地幔(OIB)部分熔融。中亚造山带西段的玄武岩、基性岩墙和超镁铁-镁铁杂岩主要来自被俯冲带熔体交代的强烈亏损的岩石圈地幔,其中部分地区可能有软流圈物质的加入,如东天山和阿勒泰南缘高Ti系列的玄武质岩石。根据元素和同位素地球化学资料,将巴楚大火成岩省分为2个地幔省(mantledomain),即塔里木省和中亚省。这2个不同地幔省的成矿系列也有显著的差异,塔里木省为钒-钛磁铁矿矿床,而中亚则以铜-镍-(铂族金属)硫化物矿床为主,成矿作用的差异和岩浆地幔源区的差异是完全对应的。综合地质、地球化学和成矿作用,认为巴楚大火成岩省的形成和二叠纪地幔柱密切相关。     

塔里木二叠纪基性-中性-酸性岩浆岩的年代学及其地质意义

塔里木西部柯坪地区出露的早二叠纪玄武岩与盆地内其他地区广泛分布的玄武岩共同构成一个面积约0.25Mkm²的溢流玄武岩省。巴楚地区出露的早二叠纪辉绿岩、正长岩、石英正长岩与石英正长斑岩等多种岩浆岩构成了连续的基性-中性-酸性岩浆序列。野外露头观察表明,巴楚麻扎尔塔格地区的基性-中性-酸性岩浆岩为近同时侵位。柯坪塔格开派兹雷克组顶部层位玄武岩的锆石SHRIMP U-Pb年龄为279.0±4.5Ma, 该年龄值可限定该区二叠纪溢流玄武岩喷发的最晚时限。巴楚麻扎尔塔格石英正长斑岩脉的锆石SHRIMP U-Pb年龄为273.0±3.7Ma, 与前人测定的巴楚辉绿岩脉和正长岩的锆石年龄在误差范围内一致,表明巴楚地区的基性-中性-酸性岩浆岩为近同时侵位,时间在275Ma左右。综合已发表的塔里木二叠纪岩浆岩高精度年代数据,本文提出：整个塔里木大火成岩省岩浆作用的持续时间约为20Myrs; 291~287Ma喷发的巨量溢流玄武岩可能构成塔里木大火成岩省的主体,是地幔柱头部熔融的直接产物; 283~272Ma侵位的巴楚、一间房和塔北地区的其它类型岩浆岩体积较小,为塔里木大火成岩省晚期岩浆作用的产物。     

Two magma series and associated ore deposit types in the Permian Emeishan large igneous province, SW China

The Late Middle Permian ( 260 Ma) Emeishan large igneous province in SW China contains two magmatic series, one comprising high-Ti basalts and Fe-rich gabbroic and syenitic intrusions, the other low-Ti basalts and mafic–ultramafic intrusions. The Fe-rich gabbros are spatially and temporally associated with syenites. Each series is associated with a distinctive type of mineralization, the first with giant Fe–Ti–V oxide ore deposits such as Panzhihua and Baima, the second with Ni–Cu–(PGE) sulfide deposits such as Jinbaoshan, Limahe and Zhubu. New SHRIMP zircon U–Pb isotopic data yielded 263 ± 3 Ma for the Limahe intrusion, 261 ± 2 Ma for the Zhubu intrusion and 262 ± 2 Ma for a syenitic intrusion. These new age dates, together with previously reported SHRIMP zircon U–Pb ages, suggest that all these intrusions are contemporaneous with the Emeishan flood basalts and formed during a major igneous event at ca. 260 Ma.The oxide-bearing intrusions have higher Al₂O₃, FeO (as total iron) and total alkalis (Na₂O + K₂O) but lower MgO than the sulfide-bearing intrusions. All intrusions are variably enriched in LREE relative to HREE. The oxide-bearing intrusions display positive Nb- and Ti-anomalies and in certain cases negative Zr–Hf anomalies, whereas the sulfide-bearing intrusions have obvious negative Nb- and Ti-anomalies, a feature of crustal contamination. Individual intrusions have relatively small ranges of Nd(t) values. All the intrusions, however, have Nd(t) values ranging from − 3.9 to + 4.6, and initial ⁸⁷Sr/⁸⁶Sr ratios from 0.7039 to 0.7105. The syenites have very low MgO (< 2 wt.%) but highly variable Fe₂O₃ (2.5 to 13 wt.%) with initial ⁸⁷Sr/⁸⁶Sr ratios ranging from 0.7039 to 0.7089. Magmas from both series could have derived by melting of a heterogeneous mantle plume: the high-Ti series from a Fe-rich, more fertile source and the low-Ti series from a Fe-poor, more refractory source. In addition, the low-Ti series underwent significant crustal contamination. The two magma series evolved along different paths that led to distinct mineralization styles.     

塔里木地块西北缘震旦系发现二叠纪基性岩床侵入事件

准确识别侵入岩和火山岩并厘定其形成时代是野外地质调查的一项基础工作,它们对认识区域岩浆事件序列和建立沉积地层年代格架具有重要的作用。塔里木地块西北缘阿克苏地区以出露连续的新元古界和丰富多样的新元古代岩浆岩而成为备受前寒武纪地质研究工作者关注的地区。本文通过遥感影像的识别、野外剖面地质调查和岩石学研究,发现塔里木西北缘阿克苏市西南部的震旦系中发育的基性岩具有典型的岩浆侵入特征,包括局部截切地层、包裹围岩块和内部结晶粗、边缘结晶细等特点。结合锆石U-Pb年代学研究,发现该地区震旦系发育的基性岩浆岩并不全是震旦纪玄武岩,有相当一部分是早二叠世(ca. 290Ma)侵入的辉绿岩岩床,其侵位年龄与塔里木二叠纪大规模溢流玄武岩的喷发时代接近,很可能是塔里木大火成岩省的重要组成部分。这期显著的岩浆热事件可能对该地区前寒武纪岩石重磁化产生重要影响,同时也启示今后开展塔里木北缘震旦纪岩浆作用研究时需要特别引起重视并加以仔细鉴别。     

Microstructural evidence for magma confluence and reusage of magma pathways: implications for magma hybridization,Karakoram Shear Zone in NW India

In the Karakoram Shear Zone, Ladakh, NW India, Miocene leucogranitic dykes form an extensive, varied and complex network, linking an anatectic terrane exposed in the Pangong Range, with leucogranites of the Karakoram Batholith. Mineral paragenesis of the heterogeneous anatectic source rocks suggests melting has resulted from water influx into rocks at upper amphibolite facies conditions, and microstructures suggest anatexis was contemporaneous with shearing. The network is characterized by continuous and interconnected dykes, with only rare cross‐cutting relationships, forming swarms and chaotic injection complexes where magmatic rocks cover up to 50% of the outcrop area. Despite this volume of magma, the system did not lose continuity, suggesting that it did not flow en masse and that the magma network was not all liquid simultaneously. Leucogranites in this network, including leucosomes in migmatites, carry an isotopic signature intermediate between the two main anatectic rocks in the source, suggesting efficient homogenization of the magmatic products. Here, we describe a number of microscopic features of these magmatic rocks which suggests that several pulses of magma used the same pathways giving rise to textural and chemical disequilibrium features. These include: (i) narrow, tortuous corridors of fine‐grained minerals cutting across or lining the boundaries of larger grains, interpreted to be remnants of magma‐filled cracks cutting across a pre‐existing magmatic rock; (ii) corrosion of early formed grains at the contact with fine‐grained material; (iii) compositional zoning of early formed plagioclase and K‐feldspar grains and quartz overgrowths documented by cathodoluminescence imaging; (iv) incipient development of rapakivi and anti‐rapakivi textures, and (iv) different crystallographic preferred orientation of early formed quartz and fine‐grained quartz. Mapping of the fine‐grained corridors interpreted to represent late melt channels reveal an interlinked network broadly following the S‐C fabric defined by pre‐existing magmatic grains. We conclude that early formed dykes provided a pathway exploited intermittently or continuously by new magma batches. New influxes of magma opened narrow channels and migrated through a microscopic network following predominantly grain boundaries along an S‐C fabric related to syn‐magmatic shearing. A mixed isotopic signature resulted not from the mixing of magmas, but from the micro‐scale interaction between new magma batches and previously crystallized magmatic rocks, through local equilibration.     

塔里木盆地西北缘二叠纪壳源型碳酸岩的发现及其地质意义

碳酸岩是自然界较为特殊的一类火成岩,由于其在上侵过程中不易受到地壳物质的混染,可以很好地保留源区原始特征,因而在揭示岩浆源区属性和地球深部碳循环等方面具有重要的研究价值.塔里木盆地西北缘阿克苏-乌什南部地区发育多条侵位到新元古界南华系中的火成碳酸岩岩墙或岩脉.这些岩脉的锆石U-Pb测年结果显示出多个年龄峰值,其中最年轻...     

The Permian mafic intrusive events in the northwestern margin of the Tarim Basin and their tectonic significanceSCIEI北大核心CSCD

塔里木大火成岩省是我国境内发现的两个重要的二叠纪大火成省之一,不仅有大规模的溢流相玄武岩喷发,还有复杂多样的侵入岩及其组合。以往的研究主要集中在二叠系等显生宙地层发育区,对于前寒武系等古老层系中是否存在二叠纪岩浆侵入未引起重视。本文通过野外地质调查,在阿克苏地区前寒武系中识别出数条侵入南华系的基性岩墙和较大规模侵入震旦系的基性岩床。岩墙、岩床与围岩之间均显示出典型的侵入接触关系,包括岩体内部结晶粗、边部结晶细的淬冷边结构、岩床顶底面显著的切层现象以及包裹围岩团块等;显微镜下观察表明,辉绿岩具有典型的辉绿结构和嵌晶含长结构。锆石U-Pb年代学结果表明,侵入下震旦统的辉绿岩岩床和侵入南华系的辉绿岩岩墙的侵位时代在误差范围内基本一致,约为290Ma。岩石地球化学特征表明,辉绿岩岩床具有与洋岛玄武岩(OIB)相似的稀土及微量元素配分模式,结合Sr-Nb-Pb同位素测试结果,认为它们来源于碳酸盐化的富集型岩石圈地幔部分熔融,而辉绿岩岩墙具有Nb、Ta、Zr、Hf等负异常的地球化学特征,可能来自曾被俯冲相关流体/熔体交代的岩石圈地幔源区。本文的早二叠世辉绿岩岩床和岩墙的形成时代、岩浆源区和岩浆演化...     

Crust-derived felsic magmatism in the Emeishan large igneous Province: New evidence from zircon U-Pb-Hf-O isotope from the Yangtze Block,China

Numerous intrusive bodies of mafic–ultramafic to felsic compositions are exposed in association with volcanic rocks in the Late Permian Emeishan large igneous province (ELIP), southwestern China. Most of the granitic rocks in the ELIP were derived by differentiation of basaltic magmas with a mantle connection, and crustal magmas have rarely been studied. Here we investigate a suite of mafic dykes and I-type granites that yield zircon U-Pb emplacement ages of 259.9 ± 1.2 Ma and 259.3 ± 1.3 Ma, respectively. The ε_Hf(t) values of zircon from the DZ mafic dyke are –0.3 to 9.4, and their corresponding T_DM1 values are in the range of 919–523 Ma. The ε_Hf(t) values of zircon from the DSC I-type granite are between –1 and 3, with T_DM1 values showing a range of 938–782 Ma. We also present zircon O isotope data on crust-derived felsic intrusions from the ELIP for the first time. The δ¹⁸O values of zircon from the DSC I-type granite ranges from 4.87‰ to 7.5‰. The field, petrologic, geochemical and isotopic data from our study lead to the following salient findings. (i) The geochronological study of mafic and felsic intrusive rocks in the ELIP shows that the ages of mafic and felsic magmatism are similar. (ii) The DZ mafic dyke and high-Ti basalts have the same source, i.e., the Emeishan mantle plume. The mafic dyke formed from magmas sourced at the transitional depth between from garnet-lherzolite and spinel-lherzolite, with low degree partial melting (<10%). (iii) The Hf-O isotope data suggest that the DSC I-type granite was formed by partial melting of Neoproterozoic juvenile crust and was contaminated by minor volumes of chemically weathered ancient crustal material. (iv) The heat source leading to the formation of the crust-derived felsic rocks in of the ELIP is considered to be mafic–ultramafic magmas generated by a mantle plume, which partially melted the overlying crust, generating the felsic magma.     

The petrogenetic interrelationship of Wajilitag complex components in the early Permian Tarim large igneous province,NW China

ABSTRACT

The Permian Tarim large igneous province (TLIP) is located in the Tarim basin, NW China. Although the flood basalt of the TLIP has been intensively studied, other igneous components within TLIP have not yet been sufficiently investigated. The Wajilitag igneous complex is outcropped with a rather limited exposure by regional tectonic uplift. However, various igneous rocks, both mafic–ultramafic and syenitic, can be observed as either intrusions or extrusions in this area. It is an ideal location for studying the magmatic evolution of different components within the TLIP. We systematically examine the geological, geochronological, and geochemical characteristics of the Wajilitag complex, to further constrain the petrogenesis of each component and their interrelationships, as well as the implications to the petrogenetic model of TLIP. The igneous rocks in Wajilitag complex can be classified into two series based on their geochemical features: Series A and Series B. Series A are more alkalic, more trace element enriched and more isotopically depleted than Series B. Series A includes nephelinite, aegirine–nepheline syenite (ANS), and syenite porphyry (SP), whereas the Series B consists of clinopyroxenite, gabbro, diorite, hornblende-bearing syenite (HS), and quartz syenite (QSN). Dolerites can either belong to Series A or Series B depend on its geochemistry. Kimberlitic rocks are independent of the Wajilitag complex geologically, geochemically, and geochronogically. The temporal sequences of Wajilitag complex would be clinopyroxenite→gabbro→ diorite/syenite→nephelinite. The dolerite can be emplaced later than the syenite but can extend to an earlier period. In contrast to the Tarim basalts, the Wajilitag complex belongs to the second stage of magmatism in the TLIP. The mantle source for the Tarim basalts, the Series B and Series A gradually changed from SCLM-dominated to plume-dominated component.     

新疆尾亚地区岩浆混合作用的年代学证据

新疆东部尾亚矿区的钾长花岗岩及其包体岩相学、矿物化学和岩石地球化学特征及野外地质特征显示其为岩浆混合作用的结果。本文获得钾长花岗岩及其中暗色微粒包体闪长岩锆石U-Pb年龄为(247.5±5.3)Ma和(244.8±1.8)Ma,与该区石英二长闪长岩体的锆石U-Pb年龄(244.7±3.3)Ma在误差范围内一致,这一结果从年代学角度为钾长花岗岩及其中暗色微粒包体的岩浆混合作用成因提供证据。