Shear wave velocity structure beneath the Archaean granites around Hyderabad, inferred from receiver function analysis

Broadband receiver functions abstracted from teleseismicP waveforms recorded by a 3-component Streckeisen seismograph at Hyderabad, have been inverted to constrain the shear velocity structure of the underlying crust. Receiver functions obtained from the Hyderabad records of both shallow and intermediate focus earthquakes lying in different station-event azimuths, show a remarkable coherence in arrival times and shapes of the significant shear wave phases:Ps, PpPs, PsPs/PpSs, indicating horizontal stratification within the limits of resolution. This is also supported by the relatively small observed amplitudes of the tangential component receiver functions which are less than 10% of the corresponding radial component. Results of several hundred inversions of stacked receiver functions from closely clustered events (within 2°), show that the crust beneath the Hyderabad granites has a thickness of 36 ± 1 km, consisting of a 10 km thick top layer in which shear wave velocity is 3.54 ± 0.07 km/sec, underlain by a 26 ± 1 km thick lower crust in which the shear wave velocity varies uniformly with a small gradient of 0.02 km/sec/km. The shear wave velocity at its base is 4.1 ± 0.05 km/sec, just above the moho transition zone which is constrained to be less than 4 km thick, overlying a 4.74 ±0.1 km/sec half space.     

Crustal structure of the Kaapvaal craton and its significance for early crustal evolution

High-quality seismic data obtained from a dense broadband array near Kimberley, South Africa, exhibit crustal reverberations of remarkable clarity that provide well-resolved constraints on the structure of the lowermost crust and Moho. Receiver function analysis of Moho conversions and crustal multiples beneath the Kimberley array shows that the crust is 35 km thick with an average Poisson's ratio of 0.25. The density contrast across the Moho is 15%, indicating a crustal density about 2.86 gm/cc just above the Moho, appropriate for felsic to intermediate rock compositions. Analysis of waveform broadening of the crustal reverberation phases suggests that the Moho transition can be no more than 0.5 km thick and the total variation in crustal thickness over the 2400 km² footprint of the array no more than 1 km. Waveform and travel time analysis of a large earthquake triggered by deep gold mining operations (the Welkom mine event) some 200 km away from the array yield an average crustal thickness of 35 km along the propagation path between the Kimberley array and the event. P- and S-wave velocities for the lowermost crust are modeled to be 6.75 and 3.90 km/s, respectively, with uppermost mantle velocities of 8.2 and 4.79 km/s, respectively. Seismograms from the Welkom event exhibit theoretically predicted but rarely observed crustal reverberation phases that involve reflection or conversion at the Moho. Correlation between observed and synthetic waveforms and phase amplitudes of the Moho reverberations suggests that the crust along the propagation path between source and receiver is highly uniform in both thickness and average seismic velocity and that the Moho transition zone is everywhere less than about 2 km thick. While the extremely flat Moho, sharp transition zone and low crustal densities beneath the region of study may date from the time of crustal formation, a more geologically plausible interpretation involves extensive crustal melting and ductile flow during the major craton-wide Ventersdorp tectonomagmatic event near the end of Archean time.     

龙门山多层分层拆离地壳结构:新构造变形与深部构造证据

2008年5.12汶川地震发生后,对于龙门山地壳结构及其与汶川地震的成生联系成为构造地质学研究极为关注的科学问题。然而,现有的多种龙门山地壳结构模式在综合解释表层构造变形及深部构造时与调查和探测资料均有不符。利用前人地球物理探测成果,结合穿过龙门山主要发震构造单元彭灌杂岩及雪隆包岩体的综合构造剖面,将地表构造与深部地壳探测资料结合进行了综合解释,认为龙门山逆冲构造带中的多重冲断推覆构造由约10 km深处的拆离断层分隔,因而应该只是浅层次构造变形的组合样式;在中、下地壳韧性流壳层的主导下,扬子地块基底被动?入并形成多层拆离的韧性流变构造组合。5.12汶川地震及余震是由于以彭灌杂岩和雪隆包岩体为代表的刚性体,在上部韧性流壳层前端的持续推挤作用下,发生破裂而形成的。     

青藏高原东部壳幔速度结构和地幔变形场的研究

在青藏高原东部地球动力学问题中,笔者在文中主要考虑与地壳上地幔速度结构和地幔变形场有关的问题,它涉及当前流行的下地壳流动模型和壳-幔的耦合-解耦模型。在2000年完成的穿过川西高原和四川盆地的深地震测深剖面,揭示了川西高原的地壳结构具有地壳增厚(主要是下地壳增厚)、地壳平均速度低等特点,显示地壳的缩短与增厚的碰撞变形特征。根据川西高原上设置各爆炸点的记录截面图共同呈现PmP(莫霍界面反射波)弱能量的特点,推断在川西高原的下地壳介质具有强衰减(Qp=100～300)的性质,支持存在下地壳流动的模型。青藏高原东部和川滇西部地区的上地幔各向异性(SKS波快波偏振方向和快慢波延迟时间)的初步结果表明,这两个地区的壳-幔变形特征是不同的,尽管它们在地理位置上属于同一个板块碰撞带。在青藏高原内部的壳幔变形属于垂直连贯变形,它以缩短为主,而高原外部的地壳(或岩石圈)则相对于其下方地幔运动。在高原内部和外部之间存在一个重要的地幔变形过渡带。然而,高原内部的垂直连贯变形与高原内部存在大范围下地壳流动的模型不一致。笔者在该地区开展了近两年的宽频带流动地震观测,试图从地震记录中确定过渡带的位置和探讨它的流变性质。文中扼要回顾已经取得的结果,并介绍正在进行的研究。     

Crustal structure of the western Arafura Sea from ocean bottom seismograph data

Refraction data taken from ocean bottom seismograph recordings in the western Arafura Sea indicate a continental‐type structure for the region. This structure is characterised by a thin column (2 km) of sediments, with velocities ranging from about to 2 to 4 km s^‐1, overlying an essentially two layer crust. The compressional wave velocities in the upper and lower crust are 5.97 and 6.52 km s^‐1, respectively, with the boundary between the layers at a depth of 11 km. Very weak mantle‐refracted arrivals with a velocity of about 8.0 km s^‐1 were recorded. Large‐amplitude, later arrivals, beginning at distances near 100 and 150 km, have been interpreted to be part of the retrograde branches from the 8.0 and 7.33 km s^‐1 layers, respectively. Model studies indicate that a small positive velocity gradient is required between 17 and 30 km, and that the Moho is at a depth of 34 km. A third set of large amplitude, later arrivals starting at a distance near 250 km has been interpreted as most probably multiple refraction‐reflection arrivals from the 5.97 and 6.52 km s^‐1 layers. Correlation of this structure with the stratigraphic logs from exploratory oil wells in the Arafura Sea using layer velocities indicates that rocks younger than Jurassic appear to thin towards the east.     

Seismically constrained two-dimensional crustal thermal structure of the cambay basin

The temperature field within the crust is closely related to tectonic history as well as many other geological processes inside the earth. Therefore, knowledge of the crustal thermal structure of a region is of great importance for its tectonophysical studies. This work deals with the two-dimensional thermal modelling to delineate the crustal thermal structure along a 230 km long Deep Seismic Sounding (DSS) profile in the north Cambay basin. In this work P-wave velocities obtained from the DSS studies have been converted into heat generation values for the computation of temperature distribution. The model result reveals the Curie isotherm at a depth of ≈22 km and Moho temperature at around 900‡C.     

哈尔滨地区地壳稳定性研究

客观评价城市区域地壳稳定性,对于城市安全与可持续发展有着极其重要的意义.哈尔滨城市地质调查系统地研究了哈尔滨地区的莫霍面深度、地球物理场、火成岩特征及历史地震记录,并开展大地电磁测深、钻探及汞气测量研究,认为哈尔滨地区地壳结构连续、完整、稳定,不会发生中等强度及以上地震活动.     

The upper Coniacian to upper Santonian drowned Arabian carbonate platform,the Mardin-Mazidag area,SE Turkey: Sedimentological,stratigraphic, and ichthyofaunal records

A measured stratigraphic section including the upper Coniacian – upper Santonian interval in the Mardin-Mazidag area in Southeastern Turkey lies on the Arabian Platform and documents the drowning of the Arabian platform. The studied succession transgressively overlies the exposed carbonate platform and exhibits a relatively condensed sequence characterized by presence of fish remains, phosphate nodules, oncoids, phosphatic fragments, glauconites and planktonic foraminifera. Calcareous nannofossils attest a late Coniacian to late Santonian age (zones UC11 UC12). Numerous elasmobranch teeth are also present in this pelagic facies, representing mackerel sharks (Squalicorax, Pseudocorax and Scapanorhynchus) and a ray (Ctenopristis). The presence of pelagic facies and phosphate deposits on the drowned platform may indicate a sudden rise of sea level and increase of nutrient due to upwelling currents. The collapse parts of the Arabian carbonate platform occurred earlier than previously reported, starting from late Coniacian-Santonian onwards.     

苏鲁—大别超高压变质带地壳速度结构及其俯冲、折返机制

三维P波速度解析研究结果表明，苏鲁-大别超高压变质带岩石圈地壳速度结构均具有上地壳明显高速且上凸、中地壳增厚、下地壳埋藏较深且莫霍面下凹等基本特征。与大别地区相比较，苏鲁超高压变质带存在着上地壳波速更高，且地表高速区面积与上地壳高速体体积大于大别；而莫霍面下凹程度不如大别地区，地壳山根已逐步趋向消失等独特的区域特征。显示了苏鲁地区曾发生过更激烈的俯冲与折返构造运动，与大别地区相比，有更多高速、高密度的超高压变质岩折返到上地壳与地表；然而在造山运动过程中比大别更早进入了造山运动后期等特征。对比研究结果表明，苏鲁-大别地段的造山、演化过程中，在构造运动基本相似的背景下，存在着区域性特征。苏鲁地区的造山运动以及超高压变质作用，有起始略晚、发生时期较短但相对激烈、结束早、比大别更早进入了造山运动的后期等特征。笔者分析了苏鲁区域性特征形成的主要构造原因是，郯庐断裂带的大规模左旋走滑运动以及通过中国华北区域的大范围NXV—SE向扩张应力场的影响。其中，中生代以来大华北地区的大区域扩张应力场的影响可能是该区俯冲到地幔内的超高压变质岩能够大量折返回地表或上地壳的重要构造原因。     

Asymmetric crustal structure of the ultraslow-spreading Mohns Ridge

ABSTRACT

New analysis of the geophysical data of the ultraslow-spreading Mohns Ridge and its off-axis structure reveals a distinctive asymmetric structure. We calculate residual bathymetry (RB) and residual mantle Bouguer gravity anomaly (RMBA) and decompose the anomalies into symmetric and asymmetric components between the ridge conjugates. The western flank of the Mohns Ridge at crustal age of ~50–15 Ma is characterized by a broad zone of elevated RB and more negative RMBA, which we term the Vesteris Plateau (VP). The VP anomaly has a surface area of ~1.12 × 10⁵ km² and an excess crust volume of ~2.33 × 10⁵ km³, making it a significant anomaly comparable to other anomalies such as the Bermuda Rise. Extending north of the Kolbeinsey Ridge for more than 500 km, the VP lies above an anomalous upper mantle region of low shear-wave seismic velocity, indicating that the VP might represent the northernmost reach of the Iceland-Jan Mayen mantle anomaly. In addition, the western ridge flank of the Mohns Ridge at crustal age of 6–0 Ma is associated with higher RB and more positive RMBA relative to the eastern conjugate, indicating tectonic uplift and associated exposure of lower crust and upper mantle near the ridge axis.     

大别山地壳结构的Pb同位素地球化学示踪

研究了大别山东部北大别变质杂岩，南大别变质杂岩和白垩纪花岗岩的全岩Pb同位素组成，结果表明，北大别变质杂岩与南大别变质杂岩相比，前者以相对低放射成因Pb同位素组成为特征，按照Pb同位素组成在地壳垂向剖面上的变化模型，指出在大别山地壳垂向结构上，北大别变质杂岩应位于南大别变质杂岩之下，这一认识得到大别山不同构造岩石单元中产出的白垩纪花岗岩Pb同位素对岩浆源区示踪的有力支持，因此南大别超高压变质带是发育在北大别杂岩之上的一个构造岩片，这对进一步确定扬子克拉通向华北克拉通俯冲－碰撞的缝合线位置具有重要意义。     

北山构造带南部上地壳二维初至波层析成像

花海盆地—北山构造带南部位于青藏高原东北缘以北地区,是特提斯洋和古亚洲洋两大构造域的交接部位,自新元古代晚期以来经历了多期次、多阶段的板块裂解-俯冲-碰撞-拼合的演化历史,尤其是中生代以来的逆冲推覆和走滑作用,以及受新生代以来印度板块和欧亚板块碰撞的远程效应影响,导致青藏高原东北缘的向北扩展,形成了现今复杂的地质地貌结构。其地壳结构记录了多期构造作用的叠加,上地壳结构更是促进我们理解青藏高原东北缘向外的扩展机制及其对周缘块体的改造作用的天然记录本。本文利用2018年中国地质科学院在北山构造带南部完成的180 km深反射地震剖面的初至波(Pg震相)数据,通过层析成像反演方法,获得了花海盆地—北山构造带4 km深度范围内的上地壳P波速度结构。其主要特征为:花海盆地、总口子盆地和扎格高脑盆地均表现为较低的速度和较小的垂向速度梯度;研究区内的晚古生代花岗岩体具有明显的高速异常和较大的垂向速度梯度特征;左行走滑的阿尔金断裂带在花海盆地内表现为向北倾的高角度走滑性质,深度至少切穿花海盆地基底;北山南缘断裂带的推测隐伏区呈现速度等值线下凹的低速异常特征。同时,反演揭示的多处低速异常区指示了北山构造带南部的多处断层发育情况。     

苏鲁造山带区域地壳山根结构特征

本利用苏鲁大别造山带及其邻区的三维P波速度资料,详细对比研究了苏鲁与大别超高压变质带莫霍面深度和深部P波速度结构分布特征。结果表明,尽管苏鲁、大别超高压变质带都具有上地壳明显高速且上凸;中地壳增厚;下地壳埋藏较深且下凹等共同的P波速度结构特征,与大别地区相比较,苏鲁超高压变质带还存在着独特的区域性特征。从地貌上看,苏鲁地区山脉已经基本消失。苏鲁超高压变质带的地壳厚度为32～33公里,深于其周围地区2～3公里,但是莫霍面下凹程度远不如大别地区,造山带地壳山根已逐步趋向消失。苏鲁地区上地壳P波速度高于大别,比其周围地区约快1～1．2km/s,有可能显示了该区有更多高速、高密度的超高压变质岩折返到上地壳与地表的岩石物性效果。大别造山带山脉依然存在,莫霍面下凹更明显,沿NWW向串状残留地壳山根最深为37～38公里,深于其周围地区3～4公里。对比研究结果表明,由于区域构造运动的作用,苏鲁大别造山带中的不同地段,在其造山、演化过程中也存在着差别。苏鲁的造山运动起始虽略晚于大别,但结束的更快,比大别更早进入了造山运动的后期。分析促使苏鲁造山运动进程加速的主要构造原因可能有两点,郯庐断裂带的左旋走滑运动以及通过中国华北区域的大范围NW-SE向扩张应力场的影响。大区域构造背景加速了苏鲁造山带地表高山侵蚀过程的同时,随着山根浮力的不断减弱,地壳深部山根逐渐趋向消失。地壳速度结构特征有可能反映了苏鲁造山带的地壳山根随着地表山脉的侵蚀而减弱,趋向消失的过程。     

南海东北陆缘的地壳速度结构及其构造意义:来自广角地震剖面的约束

南海东北部深部地壳结构蕴含着南海陆缘伸展张裂过程的重要信息。在南海东北陆缘布设的一条广角地震测线(DP13)沿NW-SE方向依次穿过东沙隆起和台西南盆地。本文利用射线追踪和正演走时拟合软件RayInvr构建地壳纵波速度结构,模型表明：沉积层速度1.6～4.6 km/s,厚度0.5～3.8 km,横向分布不均匀,沉积基底起伏剧烈;莫霍面埋藏深度由陆架区的25.5 km急剧减小到陆坡下方的13 km,随后向下陆坡远端增深至16 km;陆架处东沙隆起下方地壳厚度从～25 km减薄到～21 km,下陆坡远端地壳厚约10～13 km,地壳拉张因子分别为1.3～1.5和2.6～3.1,表现为轻微和中等减薄;陆坡区台西南盆地内地壳厚度从17 km急剧减薄至7～8 km,地壳拉张因子高达4.6,呈超伸展减薄;地壳厚度由陆向海非单调减薄,地壳伸展具有明显的空间差异性;陆架-上陆坡和下陆坡下地壳底部发现两个相对孤立的不连续高速体,速度分别为7.0～7.5 km/s和7.0～7.3 km/s,厚度分别3～5 km和1～3 km,前者位于古太平洋俯冲带前缘,几乎与南海东北部高磁异常重叠,推测由中生代古太平洋板...     

Upper crustal structure of the Tamworth Belt,New South Wales: constraints from new gravity data

New gravity data along five profiles across the western side of the southern New England Fold Belt and the adjoining Gunnedah Basin show the Namoi Gravity High over the Tamworth Belt and the Meandarra Gravity Ridge over the Gunnedah Basin. Forward modelling of gravity anomalies, combined with previous geological mapping and a seismic-reflection transect acquired by Geoscience Australia, has led to iterative testing of models of the crustal structure of the southern New England Fold Belt, which indicates that the gravity anomalies can generally be explained using the densities of the presently exposed rock units. The Namoi Gravity High over the Tamworth Belt results from the high density of the rocks of this belt that reflects the mafic volcanic source of the older sedimentary rocks in the Tamworth Belt, the burial metamorphism of the pre-Permian units and the presence of some mafic volcanic units. Modelling shows that the Woolomin Association, present immediately east of the Peel Fault and constituting the most western part of the Tablelands Complex, also has a relatively high density of 2.72 – 2.75 t/m³, and this unit also contributes to the Namoi Gravity High. The Tamworth Belt can be modelled with a configuration where the Tablelands Complex has been thrust over the Tamworth Belt along the Peel Fault that dips steeply to the east. The Tamworth Belt is thrust westward over the Sydney – Gunnedah Basin for 15 – 30 km on the Mooki Fault, which has a shallow dip (～25°) to the east. The Meandarra Gravity Ridge in the Gunnedah Basin was modelled as a high-density volcanic rock unit with a density contrast of 0.25 t/m³ relative to the underlying rocks of the Lachlan Fold Belt. The modelled volcanic rock unit has a steep western margin, a gently tapering eastern margin and a thickness range of 4.5 – 6 km. These volcanic rocks are assumed to be Lower Permian and to be the western extension of the Permian Werrie Basalts that outcrop on the western edge of the Tamworth Belt and which have been argued to have formed in an extensional basin. Blind granitic plutons are inferred to occur near the Peel Fault along the central and the southern profiles.     

Microbial dolomite crusts from the carbonate platform off western India

Abstract The occurrence of Late Pleistocene dolomite crusts that occur at 64 m depth on the carbonate platform off western India is documented. Dolomite is the most predominant mineral in the crusts. In thin section, the crust consists of dolomitized microlaminae interspersed with detrital particles. Under scanning electron microscopy, these laminae are made up of tubular filaments or cellular structures of probable cyanobacterial origin. Dolomite crystals encrust or overgrow the surfaces of the microbial filaments and/or cells; progressive mineralization obliterates their morphology. Well-preserved microbial mats, sulphide minerals (pyrrhotite and marcasite) and the stable isotope composition of dolomite in the crusts indicate hypersaline and anoxic conditions during dolomite formation. The crusts are similar to dolomite stromatolites, and biogeochemical processes related to decaying microbial mats under anoxic conditions probably played an important role in dolomite precipitation. The dolomite is therefore primary and/or very early diagenetic in origin. The dolomite crusts are interpreted to be a composite of microbial dolomite overprinted by early burial organic dolomite. The results of this study suggest that a microbial model for dolomite formation may be relevant for the origin of ancient massive dolomites in marine successions characterized by cryptalgal laminites. The age of the crusts further suggests that the platform was situated at shallow subtidal depths during the Last Glacial Maximum.     

Mantle flow-induced crustal thinning in the area between the easternmost part of the Anatolian plate and the Arabian Foreland (E Turkey) deduced from the geological and geophysical data

Eastern Anatolia consisting of an amalgamation of fragments of oceanic and continental lithosphere is a current active intercontinental contractional zone that is still being squeezed and shortened between the Arabian and Eurasian plates. This collisional and contractional zone is being accompanied by the tectonic escape of most of the Anatolian plate to the west by major strike-slip faulting on the right-lateral North Anatolian Transform Fault Zone (NATFZ) and left-lateral East Anatolian Transform Fault Zone (EATFZ) which meet at Karlıova forming an east-pointing cusp. The present-day crust in the area between the easternmost part of the Anatolian plate and the Arabian Foreland gets thinner from north (ca 44 km) to south (ca 36 km) relative to its eastern (EAHP) and western sides (central Anatolian region). This thinner crustal area is characterized by shallow CPD (12–16 km), very low Pn velocities (< 7.8 km/s) and high Sn attenuation which indicate partially molten to eroded mantle lid or occurrence of asthenospheric mantle beneath the crust. Northernmost margin of the Arabian Foreland in the south of the Bitlis–Pötürge metamorphic gap area is represented by moderate CPD (16–18 km) relative to its eastern and western sides, and low Pn velocities (8 km/s). We infer from the geophysical data that the lithospheric mantle gets thinner towards the Bitlis–Pötürge metamorphic gap area in the northern margin of the Arabian Foreland which has been most probably caused by mechanical removal of the lithospheric mantle during mantle invasion to the north following the slab breakoff beneath the Bitlis–Pötürge Suture Zone. Mantle flow-driven rapid extrusion and counterclockwise rotation of the Anatolian plate gave rise to stretching and hence crustal thinning in the area between the easternmost part of the Anatolian plate and the Arabian Foreland which is currently dominated by wrench tectonics.     

The crustal structure of the western Po plain: reconstruction from integrated geological and seismic data

A reflection/refraction seismic experiment performed in 1991 in the western Po plain gave basic data to constrain the interpretation of the crustal structures across the Alps/Apennines junction zones. Two different seismic domains, north and south of the western supposed prosecution of the Villalvernia-Varzi line, are evidenced from the interpretation of the data. The boundary between the two domains is characterized by strong lateral variations from southern high to northern low velocity layers. The northward abrupt deepening of the refractor/reflector basement is followed at depth by a similar deepening of the crust/mantle boundary. The geological interpretation evidences domains with coherent and independent evolution at surface level juxtaposed along oblique discontinuities cutting across the crust. A peculiar feature is the presence of both crust and mantle north-verging wedges into the crustal structure and the overthrust at depth of the 'alpine' metamorphic crust onto the 'apenninic' nappes (Monferrato region).     

Planktonic Foraminiferal and Alkenone Records of the Last Deglaciation from the Eastern Arabian Sea

The oxygen isotope record of planktonic foraminifera from tropical core MD77194 (Eastern Arabian Sea) exhibits a clear two-step deglaciation with a brief δ¹⁸O transient event. In the tropics, this δ¹⁸O maximum could correspond to a cooling or to a change in the δ¹⁸O content of sea water. In this study, past sea-surface temperature (SST) and primary production (PP) are reconstructed from foraminiferal transfer functions and compared to values estimated from alkenone measurements. SST and PP records from both proxies indicate a 1.5–2.5°C deglacial warming, coupled with a PP decrease, and a 0.5–1°C cooling during the Younger Dryas (YD). A detailed comparison between independent micropaleontological and geochemical proxies helps us identify potential biases and thus strengthen the paleo-reconstructions.     

鲁西泰山地区新太古代闪长岩及角闪石岩岩石成因及其对地壳演化的制约

泰山地区的闪长岩及角闪石岩与TTG片麻岩在空间上密切共生,是太古宙地体的重要组成部分,探究其母岩浆性质和岩石成因,对认识华北克拉通鲁西早期大陆地壳形成与演化具有重要意义。以泰山闪长岩和角闪石岩为研究对象,开展了详细的锆石U-Pb年龄、矿物化学和全岩-矿物Sr-Nd-Hf同位素研究。LA-ICP-MS锆石U-Pb定年结果显示,1件闪长岩和2件角闪石岩样品的207Pb/206Pb年龄加权平均值分别为2615 ±8 Ma、2627 ±14 Ma和2616 ±10 Ma,与全岩-矿物（角闪石和斜长石）Rb-Sr等时线定年得到的年龄结果（2621 ±7 Ma）一致,表明二者均属于新太古代约2.6 Ga岩浆作用的产物。2个岩体形成时代及矿物地球化学特征的相似性,表明它们应为同源岩浆不同演化阶段的产物,其母岩浆在后期上升侵位过程中受到分离结晶作用的影响,而率先形成的角闪石岩受分离结晶作用影响较小。利用角闪石的成分和已知的角闪石-熔体的分配系数计算得到的与闪长岩和角闪石岩中角闪石平衡的熔体表现为低Mg#值（平均值分别为31.9和43.4）,富集Ba、Pb等大离子亲石元素,亏损Nb、Ta、Zr、Ti等高场强元素,以及具有平坦的重稀土元素配分型式。此外,岩石具有低的87Sr/86Sr初始值和接近亏损地幔的εNd（t）（-0.01~2.87）、εHf（t）（-0.76~4.89）,且两阶段Nd模式年龄TDM2为2.97~2.73 Ga。综合来看,研究区闪长岩和角闪石岩的母岩浆可能来自于幔源岩浆底侵引起新生基性下地壳在角闪岩相条件下熔融形成的安山质母岩浆;该母岩浆经历了以斜长石、角闪石等矿物为主的结晶分异。鲁西地区在2.9~2.7 Ga经历了大规模的大陆地壳生长,新太古代晚期2.6~2.5 Ga经历了广泛的大陆地壳重熔再造,幔源岩浆的幕式底侵作用可能是华北克拉通新太古代早期（2.8~2.6 Ga）大陆地壳生长和分异的主要动力学原因之一。