南秦岭旬阳盆地东部晚泥盆世岩浆成因钠长岩及其构造意义          下载免费PDF全文

罗金海  周亚军  徐欢  尤佳  李亦飞  车自成 《地质学报》2017,91(2):302-314

南秦岭旬阳盆地的钠长岩此前被认为是热水沉积或热液交代作用的产物。本文对南秦岭旬阳盆地东端黄石板地区侵入于下志留统梅子亚组浅变质岩中的钠长岩体进行了地球化学和锆石U-Pb LA-ICP-MS年代学研究,结果表明钠长岩具有富钠贫钾、铝不饱和、亏损大离子亲石元素K和Rb、高场强元素(Nb、Ta、Th、Hf)显著富集的地球化学特点,主体属于钙碱性系列岩石,反映幔源成因的特征。钠长岩中获得最年轻的锆石U-Pb年龄为364~376Ma,该年龄代表岩体的形成年龄,反映晚泥盆世时南秦岭旬阳盆地处于强烈的伸展构造环境。此项研究结果表明,在旬阳盆地的志留系中,岩浆成因与热水沉积成因的钠长岩可能是共存的。黄石板岩浆成因钠长岩岩体中含有大量前寒武纪和早古生代的捕获锆石,在捕获锆石中测得迄今为止在研究区及其邻区获得的最古老的锆石U-Pb年龄(3291Ma)。这些捕获锆石的测年数据说明,研究区所在的南秦岭地区可能从古太古代开始就与扬子地块具有明显的亲缘性。  相似文献   

Reconstructing the Cryogenian–Ediacaran evolution of the Porongos fold and thrust belt,Southern Brasiliano Orogen,based on Zircon U–Pb–Hf–O isotopes     

J. Pertille  L. A. Hartmann  J. O. S. Santos  N. J. McNaughton  R. Armstrong 《International Geology Review》2017,59(12):1532-1560

The Neoproterozoic geotectonic triad of the Brasiliano Orogen is reconstructed in southern Brazil from studies focused on the Porongos fold and thrust belt. We integrate field geology with isotopic studies of zircon U–Pb SHRIMP and Lu–Hf–O laser determinations in seven metasedimentary and three metavolcanic rock samples. The results indicate that the Porongos palaeo-basin was derived from mixed sources (3200–550 Ma), with major contributions from Rhyacian (2170 Ma) and Ediacaran (608 Ma) sources. Minor contributions from Archaean to Tonian sources are also registered. The maximum depositional age of the Porongos palaeo-basin is established by the age range of 650–550 Ma with T_DM model ages between 2.5 and 1.3 Ga. The reworked signature (ε_Hf values = ?34 to ?4) and the characteristic crustal magma reservoirs (δ¹⁸O ≥5.3 ‰) indicate that these sediments are equivalent to Neoproterozoic granites of the Dom Feliciano Belt. The episodic depositional history started in the Cryogenian (650 Ma) and lasted until the Ediacaran (most likely 570 Ma). A magmatic event of Tonian age is recorded in rhyodacite samples interleaved with the metasedimentary rocks and dated at 773, 801, and 809 Ma. The crustal evolution of the Sul-Riograndense Shield included mountain building, folding and thrusting and flexural subsidence in the foreland. An orogenic triad is revealed as the Pelotas Batholith, the Porongos fold and thrust belt and the Camaquã Basin, all part of the Dom Feliciano Belt.  相似文献   

Detrital zircon U–Pb ages and whole-rock geochemistry of the Neoproterozoic Paulistana and Santa Filomena complexes,Borborema Province,northeastern Brazil: implications for source area composition,provenance, and tectonic setting     

Felipe H. Santos  Wagner S. Amaral  Evilarde C. Uchôa Filho  Douglas T. Martins 《International Geology Review》2017,59(15):1861-1884

The Paulistana and Santa Filomena Complexes are situated in the southern part of the Borborema Province (northeastern Brazil), in the Riacho do Pontal Orogen, and represent meta-volcano-sedimentary sequences. We present compositional variations in the metasedimentary rocks and new U–Pb detrital zircon data. Major and trace elements indicate that the metasedimentary rocks from the Paulistana and Santa Filomena Complexes are composed mostly of immature to mature sediments derived from felsic-intermediate sources with moderate to slightly high chemical weathering. The geochemical signatures of the sediment protoliths for both complexes are characteristic of continental magmatic arc settings with minor contribution from recycled sediment sources. The source area for the Paulistana Complex rocks follow the compositional trend between calc-alkaline granites and granodiorites, whereas the Santa Filomena Complex rocks have a more restricted composition trending to more granodioritic sources. For the Paulistana Complex, two main source ages were identified: (1) Tonian (ca. 950 Ma – sample RPE-58) and Tonian–Stenian (ca. 1.0 Ga – sample RPE-103). These data coupled with geochemical information suggest that the Cariris Velhos arc system was the main source area for the Paulistana Complex. Regarding the Santa Filomena metasedimentary rocks, potential source-areas include: (1) Neoarchaean rocks (~2.6 Ga) represented by the adjacent basement rocks of the Riacho do Pontal Orogen; (2) Rhyacian–Orosirian rocks (2.2–2.0 Ga) of the Riacho do Pontal Orogen and the Pernambuco–Alagoas terrain, which include an augen-gneiss with arc-related geochemical signature; (3) Statherian granites (1.7–1.6 Ga); and (4) Cariris Velhos crust (1000–920 Ma). The metasedimentary rocks of the Paulistana Complex were deposited in a rift stage (ca. 900 Ma), which is related to the break-up of the Rodinia supercontinent. The metasedimentary rocks of the Santa Filomena Complex most probably were deposited in another rift stage (ca. 750–700 Ma) and could be correlatives of the rift formation of the Canindé Domain (Sergipano Orogen).  相似文献   

Chronological constraints on the tectonic evolution of the Chinese Tianshan Orogen through detrital zircons from modern and palaeo-river sands     

Rong Ren  Shu-Wei Guan  Bao-Fu Han  Li Su 《International Geology Review》2017,59(13):1657-1676

The Chinese Tianshan Orogen marks prolonged and complicated interactions between the southwestern Palaeo-Asian Ocean and surrounding blocks. New and previously published detrital zircon chronological data from modern and palaeo-river sands were compiled to reveal its tectonic evolution. It is characterized by predominant Palaeozoic as well as minor Mesozoic and Precambrian detrital zircon ages with a multimodal characteristic. The oldest Phanerozoic zircon population (peaking at 475 Ma) is a result of subduction and closure of the early Palaeozoic Terskey Ocean. However, the absence of this peak in the Chinese North and southern South Tianshan suggests that subductions of the North and South Tianshan oceans may not have initiated until the Late Ordovician with subsequent 460–390 and 360–320 Ma arc magmatism. Similar to the magmatic suite in classic collisional orogens, the youngest massive 320–270 Ma magmatism is suggested to be post-collisional. The North and South Tianshan oceans therefore probably had their closure to form the Chinese Tianshan Orogen during the late Carboniferous. The weak Mesozoic intra-plate magmatism further rejects a late Permian–Triassic Tianshan Orogen due to a lack of extensive syn- and post-collisional magmatism. Moreover, diverse Precambrian detrital zircon age patterns indicate that the surrounding blocks have distinct evolutionary processes with short-term amalgamation during the Meso- to Neoproterozoic.  相似文献   

Paleogene magmatism and gold metallogeny of the Jinping terrane in the Ailaoshan ore belt,Sanjiang Tethyan Orogen (SW China): Geology,deposit type and tectonic setting     

《Ore Geology Reviews》2017

The Jinping terrane is situated in the southern segment of the Ailaoshan ore belt, Sanjiang Tethyan Orogen (SW China). The Paleogene intrusions in Jinping consist of syenite porphyry, fine-grained syenite and biotite granite stocks/dikes, and contain relatively low TiO₂ (0.21–0.38 wt%), P₂O₅ (0.01–0.35 wt%), and high Na₂O (2.00–4.62 wt%) and K₂O (4.48–7.06 wt%), belonging to high-K alkaline series. Paleogene gold mineralization in Jinping comprises four genetic types, i.e., orogenic, alkali-rich intrusion-related, porphyry and supergene laterite. The NW–NNW-trending faults and their subsidiaries are the major ore-controlling structures. The orogenic Au mineralization, dominated by polymetallic sulfide-quartz veins, occurs in the diorite and minor in Silurian-Devonian sedimentary rocks. It contains a CO₂-rich mesothermal fluid system generated from the mixing of mantle-derived fluids with crustal-derived metamorphic fluids, and the ore-forming materials were upper crustal- or orogenic-derived. The alkali-rich intrusion-related Au mineralization is hosted in the Ordovician-Silurian sedimentary rocks and minor in the Paleogene alkaline intrusions, and the Au orebodies occur predominantly in the alteration halos. It contains a CO₂-bearing, largely metamorphic-sourced mesothermal fluid system, and the ore-forming materials were derived from the ore-hosting rocks and minor from the alkali-rich intrusions. The porphyry Cu-Mo-Au mineralization occurs in the granite/syenite porphyries and/or along their contact skarn, with the mineralizing fluids being magmatic-hydrothermal in origin. The former two hypogene Au mineralization types in Jinping were mainly formed in the late Eocene (ca. 34–33 Ma) and slightly after the porphyry Cu-Mo-Au mineralization (ca. 35–34 Ma), which is coeval with the regional Himalayan orogenic event. Subsequent weathering produced the laterite Au mineralization above or near the hypogene Au orebodies.  相似文献   

The Chalukou deposit in the North Great Xing’an Range of China: A protracted porphyry Mo ore-forming system in a long-lived magmatic evolution cycle     

《Ore Geology Reviews》2017

The Chalukou deposit is located in the North Great Xing’an Range of the Xing’an-Mongolia Orogen bordering and to the northeast of the North China Craton. The deposit is a high-F-type porphyry Mo deposit hosted by the Chalukou composite igneous body containing small intrusive bodies genetically related to Mo mineralization. The composite igneous body includes pre-mineralization dolerite, monzogranite and syenogranite, syn-mineralization rhyolitic porphyry, granitic porphyry and fine-grained monzogranite, and post-mineralization rhyolitic porphyry, quartz porphyry, dioritic porphyry and andesitic porphyry. Detailed laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U-Pb zircon dating of the igneous components of the composite igneous body was carried out to determine the temporal framework for magmatism in the Chalukou region. The new LA-ICP-MS U-Pb ages constraint documented here, together with the published ages, indicate that there was a protracted porphyry Mo ore-forming event of approximately 7 million years between ca. 152 when the ore related rhyolitic porphyry was emplaced and ca.145 Ma when molybdenite ceased being deposited. The dating reveals that the mineralization is a part of relatively long-lived magmatic cycle involving the emplacement of small doleritic stocks at ca. 165 Ma that progressively evolved into extensive granitic intrusions at ca. 164 Ma, and then diminished with the emplacement of mineralization-related porphyries to ca. 152 Ma. The emplacement of barren Early Cretaceous magmatism, represented by volcanic units in the ca. 136 Ma Guanghua Formation and porphyries, followed the mineralized magmatism.The syn-mineralization porphyry units associated with Mo contain zircons assaying ∼15 times higher in U and Th than the pre-mineralization magmatic phases. This indicates that there was a significant enrichment of Mo, U and Th in the magma, and directly associated with ore fluid exsolution. The return to their normal levels in the three elements in the post-mineralization magmatic phases indicates that they were exhausted from the magma chamber in the later phases. A genetic model is proposed for the enormous introduction of ore metals and enrichment at the Chalukou deposit. The protracted and multiphase igneous activity during the long-lived magmatism reflects a multistage enrichment of metal, and may play a crucial role in the formation of a volatile-enriched, fertile and large-volume magma chamber beneath the Chalukou deposit. Such a chamber is envisaged to be required for the formation of porphyry Mo deposits in general.  相似文献   

Mid to late Paleozoic shortening pulses in the Lachlan Orogen,southeastern Australia: a review   总被引：1，自引：1，他引：0  

C. L. Fergusson 《Australian Journal of Earth Sciences》2017,64(1):1-39

In the late Silurian, the Lachlan Orogen of southeastern Australia had a varied paleogeography with deep-marine, shallow-marine, subaerial environments and widespread igneous activity reflecting an extensional backarc setting. This changed to a compressional–extensional regime in the Devonian associated with episodic compressional events, including the Bindian, Tabberabberan and Kanimblan orogenies. The Early Devonian Bindian Orogeny was associated with SSE transport of the Wagga–Omeo Zone that was synchronous with thick sedimentation in the Cobar and Darling basins in central and western New South Wales. Shortening has been controlled by the margins of the Wagga–Omeo Zone with partitioning along strike-slip faults, such as along the Gilmore Fault, and inversion of pre-existing extensional basins including the Limestone Creek Graben and the Canbelego–Mineral Hill Volcanic Belt. Shortening was more widespread in the late Early Devonian to Middle Devonian Tabberabberan Orogeny, with major deformation in the Melbourne Zone, Cobar Basin and eastern Lachlan Orogen. In the eastern Melbourne Zone, structural trends have been controlled by the pre-existing structural grain in the adjacent Tabberabbera Zone. Elsewhere Tabberabberan deformation involved inversion of pre-existing rifts resulting in a variation in structural trends. In the Early Carboniferous, the Lachlan Orogen was in a compressional backarc setting west of the New England continental margin arc with Kanimblan deformation most evident in Upper Devonian units in the eastern Lachlan Orogen. Kanimblan structures include major thrusts and associated fault-propagation folds indicated by footwall synclines with a steeply dipping to overturned limb adjacent to the fault. Ongoing deformation and sedimentation have been documented in the Mt Howitt Province of eastern Victoria. Overall, structural trends reflect a combination of controls provided by reactivation of pre-existing contractional and extensional structures in dominantly E–W shortening operating intermittently from the earliest Devonian to Early Carboniferous.  相似文献   

The lithospheric transition between the Delamerian and Lachlan orogens in western Victoria: new insights from 3D magnetotelluric imaging     

K. E. Robertson  G. S. Heinson  D. H. Taylor  S. Thiel 《Australian Journal of Earth Sciences》2017,64(3):385-399

The magnetotelluric (MT) method was used to image the crust and upper mantle beneath the Delamerian and Lachlan orogens in western Victoria, Australia. During the Cambrian time period, this region changed from being the extended passive margin of Proterozoic Australia into an Andean-style convergent margin that progressively began to accrete younger oceanic terranes. Several broadband MT transects, which were collected in stages along coincident deep (full crust imaging) seismic reflection lines, have now been combined to create a continuous 500 km east–west transect over the Delamerian–Lachlan transition region in the Stawell Zone. We present the electrical resistivity structure of the lithosphere using both 3D and 2D inversion methods. Additionally, 1D inversions of long-period AusLAMP (Australian Lithospheric Architecture Magnetotelluric Project) MT data on a 55 km regionally spaced grid were used to provide starting constraints for the 3D inversion of the 2D profile. The Delamerian to Lachlan Orogen transition region coincides with the Mortlake Discontinuity, which marks an isotopic discontinuity in Cenozoic basalts, with higher strontium isotope enrichment ratios in the Lachlan Orogen relative to the Delamerian Orogen. Phase tensor ellipses of the MT data reveal a distinct change in electrical resistivity structure near the location of the Mortlake Discontinuity, and results of 3D and 2D inversions along the MT profile image a more conductive lower crust and upper mantle beneath the Lachlan Orogen than the Delamerian Orogen. Increased conductivity is commonly ascribed to mantle enrichment and thus supports the notion that the isotope enrichment of the Cenozoic basalts at least partially reflects an enriched mantle source rather than crustal contamination. Fault slivers of the lower crust from the more conductive Lachlan region expose Cambrian boninites and island arc andesites indicative of subduction, a process that can enrich the mantle isotopically, and also electrically, by introducing carbon (graphite) and water (hydrogen).  相似文献   

甘肃大佛寺、金佛寺花岗岩体的锆石U-Pb年龄、Hf-O同位素和全岩地球化学特征及地质意义   总被引：2，自引：0，他引：2  

孙宝璐  钱青  张建新 《岩石学报》2017,33(10):3091-3108

走廊过渡带大佛寺花岗岩为弱过铝质(A/CNK=1.03~1.06),SiO_2(76.7%~78.9%)、全碱(Na2O+K2O=7.7%~8.3%)、Rb(303×10~(-6)~383×10~(-6))、Nb(32×10~(-6)~42×10~(-6))、重稀土(Yb~8×10~(-6))含量以及和FeOT/MgO(6.3~7.6)、Ga/Al(3×10-4)、Rb/Ba(3.0~6.2)比值较高,MgO(~0.1%)、CaO(0.5%~0.6%)含量较低,Ba、Sr、Eu、Ti强烈亏损,属A型花岗岩,其源岩可能为泥质岩。大佛寺花岗岩中锆石δ18O和εHf(t)值分别为7.8‰~8.6‰(平均8.24±0.13‰)和-4.8~-2.0,Hf同位素两阶段亏损地幔模式年龄1540~1717Ma,岩浆温度达到~820℃以上。北祁连造山带北缘金佛寺花岗岩为过铝质(A/CNK=1.0~1.1),SiO_2(65.5%~75.0%)、MgO(0.6%~2.2%)、Fe2O3(1.9%~5.2%)、TiO_2(0.3%~0.8%)含量变化较大,其主量和微量元素特征与北祁连造山带的柴达诺花岗岩相似,源岩可能包括杂砂岩和角闪岩。金佛寺花岗岩的锆石δ18O为7.4%~9.7‰(平均8.03±0.36‰),εHf(t)在-0.5~+1.9之间,Hf同位素两阶段亏损地幔模式年龄为1289~1439Ma,岩浆温度达到800~900℃。走廊过渡带大佛寺花岗岩、北祁连造山带北缘金佛寺花岗岩的锆石U-Pb SIMS年龄分别为426.1±2.8Ma、424.0±1.6Ma,不同构造单元发育同时期岩浆活动以及A型花岗岩的出现,表明在~425Ma北祁连洋盆已经闭合,北祁连造山带及邻区进入到后碰撞拉伸阶段。  相似文献   

江南造山带东段九岭新元古代复式花岗岩源区性质的差异:来自地球化学及锆石Hf同位素的制约   总被引：2，自引：1，他引：1  

段政  邢光福  廖圣兵  褚平利  黄文成  朱延辉 《岩石学报》2017,33(11):3610-3634

江南造山带东段九岭新元古代花岗岩据其岩石学及野外产出特征可分为3个序次的侵入体,由早到晚依次为黑云母花岗闪长岩、英云闪长岩及黑云母二长花岗岩。本次研究的黑云母花岗闪长岩和英云闪长岩中等富硅(SiO_2分别为66.05%~75.78%和67.36%~73.94%),而黑云母二长花岗岩极富硅(SiO_2为73.96%~77.83%)。三者铝饱和指数A/CNK分别为1.53、1.71和1.32,A/NK分别为2.04、2.0和1.39,均显示典型过铝质花岗岩特征;三类岩石单元主体属高钾钙碱性系列。黑云母花岗闪长岩和英云闪长岩SiO_2与MgO、TiO_2、CaO、Fe_2O_3T、Al_2O_3、MnO、V成负相关,但黑云母二长花岗岩这种相关性不明显。黑云母花岗闪长岩和英云闪长岩均富轻稀土元素,(La/Yb)N分别平均为10.1和18.7,具弱Eu负异常(δEu分别为0.11～0.88和0.30～0.72),而黑云母二长花岗岩轻重稀土分馏弱((La/Yb)N=4.70),强烈Eu负异常(δEu=0.18～0.61)。三类岩石均富集大离子亲石元素Cs、Rb、Th、U、K、Pb,明显亏损高场强元素Nb、Ta、Sr、Ti,且锆石εHf(t)变化范围极大,分别介于-6.76～9.22、-1.08～6.63和-0.64～7.96之间。研究区北西侧和南东侧岩体锆石Hf同位素组成存在明显差异,表现为岩体北西部的锆石εHf(t)变化范围高于南东部,锆石tDM2模式年龄多集中在1.6～1.8Ga。综合研究推断本区黑云母花岗闪长岩、黑云母二长花岗岩的源区分别为砂质上地壳和泥质上地壳部分熔融产物,而英云闪长岩则为砂泥质源区部分熔融产物。同时,SE侧岩浆起源深度和岩体剥蚀程度均高于NW侧,且SE侧岩体的成岩时代也略早于NW侧,这暗示了新元古代华夏板块和扬子板块碰撞后的伸展过程中,研究区SE侧岩浆起源深度较深,且形成时代较早,并逐渐向NW侧迁移。另外,花岗质岩石源区由砂质向泥质转变的过程可能也是区域陆壳伸展作用逐渐增大的结果。  相似文献