Crustal architecture of the Capricorn Orogen,Western Australia and associated metallogeny     

S. P. Johnson  A. M. Thorne  I. M. Tyler  R. J. Korsch  B. L. N. Kennett  H. N. Cutten 《Australian Journal of Earth Sciences》2013,60(6-7):681-705

A 581 km vibroseis-source, deep seismic reflection survey was acquired through the Capricorn Orogen of Western Australia and, for the first time, provides an unprecedented view of the deep crustal architecture of the West Australian Craton. The survey has imaged three principal suture zones, as well as several other lithospheric-scale faults. The suture zones separate four seismically distinct tectonic blocks, which include the Pilbara Craton, the Bandee Seismic Province (a previously unrecognised tectonic block), the Glenburgh Terrane of the Gascoyne Province and the Narryer Terrane of the Yilgarn Craton. In the upper crust, the survey imaged numerous Proterozoic granite batholiths as well as the architecture of the Mesoproterozoic Edmund and Collier basins. These features were formed during the punctuated reworking of the craton by the reactivation of the major crustal structures. The location and setting of gold, base metal and rare earth element deposits across the orogen are closely linked to the major lithospheric-scale structures, highlighting their importance to fluid flow within mineral systems by the transport of fluid and energy direct from the mantle into the upper crust.  相似文献   

Formation and emplacement of the Dolodrook serpentinite body,Lachlan Orogen,Victoria     

《Australian Journal of Earth Sciences》2013,60(5):709-723

Serpentinised peridotite and ultramafic breccia make up an approximately 5 km‐long, 1 km‐wide fault slice within turbidites in the Dolodrook River region of the central Lachlan Orogen. The serpentinite body is surrounded by juvenile, mafic‐ultramafic sedimentary rocks with Cambrian limestone olistoliths representative of locally derived debris flows, and Middle to Upper Ordovician black shale, chert, sandstone and mudstone. The antiformal geometry and nature of the ultramafic breccia and mafic‐ultramafic sedimentary rocks (Garvey Gully Formation) indicate that the serpentinite body may have been either a former oceanic transform fault zone, a Marianas‐style serpentine seamount or a combination of these. Observations of modern‐day forearc regions show that faulting processes have led to the exposure of serpentinised peridotite horst blocks and serpentine mud volcanoes that have intruded along fault conduits (e.g. Marianas and Izu‐Bonin forearcs). At Dolodrook, the structural and metamorphic relationships with the surrounding rocks, and the lithological associations, have much in common with these observations and indicate that Dolodrook may be an ancient, on‐land example of an accreted seamount or oceanic topographic high. Structural relationships, the very low metamorphic grade of all rocks at Dolodrook, and the presence of broken formation developed in not‐fully lithified Middle to Upper Ordovician sandstone and mudstone indicate that the serpentinite body was emplaced at shallow crustal levels within the turbidite wedge (Tabberabbera Zone), possibly as an offscraped topographic high during marginal basin closure. The Dolodrook serpentinite has previously been inferred as part of the Cambrian igneous sequence (‘greenstones’) exposed in the Governor, Mt Wellington and Heathcote Fault Zones, but structural and metamorphic relationships with surrounding rocks, and the Cambrian tectonic setting in which it formed, have remained speculative.  相似文献   

Beach sand of SE Australia traced by zircon ages through Ordovician turbidites and S-type granites of the Lachlan Orogen to Africa/Antarctica: a review     

J. J. Veevers 《Australian Journal of Earth Sciences》2013,60(4):385-408

The Quaternary beach sand of SE Australia, driven northward by southern swell, contains zircons with dominant U–Pb ages of 700–500 Ma, model ages (T_DMc) of 2.2 Ga to 1.0 Ga, and ?_Hf of +12 to –30, indicating a host rock type of granitoids with alkaline affinity. These properties match those of detrital zircons in the Middle Triassic (ca 240 Ma) Hawkesbury Sandstone (T_DMc of 2.1 to 1.0 Ga, ?_Hf of +8 to –40, alkaline granitoids) and the Ordovician (ca 460 Ma) turbidites and ca 430 Ma S-type granitoids of the Lachlan Orogen (T_2DM of 2.0 to 1.0 Ga, ?_Hf of +5 to –30), all of which are identified as proximal provenances. Superimposed are the ca 400 Ma zircons in beaches in the south backed by the 420–375 Ma I-type Bega Batholith, and ca 350 Ma and ca 250 Ma zircons in the north backed by the New England Orogen. The Ordovician turbidites, part of a deep-sea super-fan, were fed by the detritus of the exhumed 700–500 Ma Transgondwanan Supermountains atop the East African–Antarctic Orogen. At the same time, the ancestral Gamburtsev Subglacial Mountains of East Antarctica probably contributed a subsidiary fan of 700–500 Ma sediment. Primary zircons aged 600–500 Ma in igneous and metamorphic rocks in Australia and the ancestral Transantarctic Mountains are minor contributors of the Australian sediments. The properties of the 700–500 Ma primary zircons in the East African–Antarctic Orogen are traceable through the first-cycle Ordovician turbidite and intruding second-cycle granite, and younger sediment, such as the third-cycle Triassic Hawkesbury Sandstone and the third-cycle beach sand. The sand at the northern terminus of the coastal system off Fraser Island spills over the shelf edge into the Tasman Abyssal Plain to reflect in miniature the deep-sea depositional environment of the Ordovician.  相似文献   

Mid- to lower-crustal architecture of the northern Lachlan and southern Thomson orogens: evidence from O–Hf isotopes     

K. Waltenberg  S. Bodorkos  R. Armstrong  B. Fu 《Australian Journal of Earth Sciences》2013,60(7-8):1009-1034

Abstract

The nature of the substrate below the northern Lachlan Orogen and the southern Thomson Orogen is poorly understood. We investigate the nature of the mid- to lower-crust using O and Lu–Hf isotope analyses of zircons from magmatic rocks that intrude these regions, and focus on the 440–410 Ma time window to minimise temporal effects while focussing on spatial differences. Over the entire region, weighted mean δ¹⁸O values range from 5.5 to 9.8‰ (relative to VSMOW, Vienna Standard Mean Oceanic Water), and weighted mean ?Hf_t range from ?8.8 to +8.5. In the northern Lachlan Orogen and much of the southern Thomson Orogen, magmatic rocks with unradiogenic ?Hf_t (～?7 to ?4) and elevated δ¹⁸O values (～9 to 10‰) reflect a supracrustal source component that may be common to both orogens. Magmatic rocks intruding the Warratta Group in the western part of the Thomson Orogen also have unradiogenic ?Hf_t (～?9 to ?6) but more subdued δ¹⁸O values (～7‰), indicating a distinct supracrustal source component in this region. Some regions record radiogenic ?Hf and mantle-like δ¹⁸O values, indicative of either a contribution from arc-derived rocks or a direct mantle input. In the northeast Lachlan Orogen Hermidale Terrane, magmatic rocks record mixing of the supracrustal source component with input from a infracrustal or mantle source component (?Hf_t as high as +8.5, δ¹⁸O values as low as 5.5‰), possibly of Macquarie Arc affinity. Samples in the west-southwestern Thomson Orogen also record some evidence of radiogenic input (?Hf_t as high as ?0.5, δ¹⁸O values as low as 6.4‰), possibly from the Mount Wright Arc of the Koonenberry Belt. Overall, our results demonstrate a strong spatial control on isotopic compositions. We find no isotopic differences between the bulk of the Lachlan Orogen and the bulk of the Thomson Orogen, and some indication of similarities between the two.  相似文献   

Geology and geochronology of the Emu Creek Block (northern New South Wales,Australia) and implications for oroclinal bending in the New England Orogen     

D. Hoy  G. Rosenbaum  R. Wormald  U. Shaanan 《Australian Journal of Earth Sciences》2013,60(8):1109-1124

The southern part of the New England Orogen exhibits a series of remarkable orogenic bends (oroclines), which include the prominent Z-shaped Texas and Coffs Harbour oroclines. The oroclines are defined by the curvature of Devonian–Carboniferous forearc basin and accretionary complex rock units. However, for much of the interpreted length of the Texas Orocline, the forearc basin is mostly concealed by younger strata, and crops out only in the Emu Creek Block in the eastern limb of the orocline. The geology of the Emu Creek Block has hitherto been relatively poorly constrained and is addressed here by presenting new data, including a revised geological map, stratigraphic sections and new detrital zircon U–Pb ages. Rocks of the Emu Creek Block include shallow-marine and deltaic sedimentary successions, corresponding to the Emu Creek and Paddys Flat formations, respectively. New detrital zircon U–Pb data indicate that these formations were deposited during the late Carboniferous and that strata were derived from a magmatic source of Devonian to Carboniferous age. The sedimentary provenance and detrital zircon age distribution suggest that the sequence was deposited in a forearc basin setting. We propose that the Emu Creek and Paddys Flat formations are arc-distal, along-strike correlatives of the northern Tamworth Belt, which is part of the forearc basin in the western limb of the Texas Orocline. These results confirm the suggestion that Devonian–Carboniferous forearc basin rocks surround the Texas Orocline and have been subjected to oroclinal bending.  相似文献   

左权-赞皇变质杂岩的地球化学特征及其构造意义   总被引：3，自引：3，他引：0  

肖玲玲  刘福来  刘建辉  刘平华  施建荣  蔡佳 《岩石学报》2013,29(2):533-550

左权变质杂岩位于华北克拉通中部造山带的中南段,赞皇变质杂岩西南。两杂岩区出露的早元古代——晚太古代变质岩石类型主要有:长英质片麻岩、黑云斜长片麻岩、斜长角闪岩、石榴角闪岩、云母片岩和长石石英岩等。通过详细地野外地质调查、岩相学以及地球化学研究发现,左权变质杂岩与赞皇变质杂岩有类似的地球化学性质,其中,长英质片麻岩、黑云斜长片麻岩和角闪岩的原岩均有正、有副,按原岩性质可分为变质沉积岩、变质花岗质岩石和变质基性岩三类。变质沉积岩的原岩为粘土岩或杂砂岩,物源以上地壳的长英质成分为主,REE配分型式与PAAS以及上地壳平均成分类似,原岩在形成过程中经历了中——低等程度的风化作用,沉积背景为有演化岛弧发育的活动大陆边缘;变质花岗质岩石的原岩为中酸性侵入岩,形成于大陆边缘弧环境,与变质沉积岩呈侵入接触关系;变质基性岩的原岩是拉斑——钙碱玄武质岩石,其稀土总量较低、轻稀土轻微富集,地壳混染作用明显,总体形成环境类似于现代大陆边缘的岛弧构造环境。基于以上地球化学特征推测左权——赞皇变质杂岩形成于典型碰撞造山环境,卷入了华北克拉通东部陆块和西部陆块之间的俯冲——碰撞过程。  相似文献   

华山太华变质杂岩中LA-ICP-MS锆石U-Pb定年及角闪石⁴⁰Ar/³⁹Ar定年   总被引：2，自引：2，他引：0  

王国栋  卢俊生  王浩  陈泓旭  肖玲玲  第五春荣  季建清  吴春明 《岩石学报》2013,29(9):3099-3114

太华变质杂岩出露于华北克拉通中部造山带最南缘,整体呈近东西向展布。华山地区的太华变质杂岩区岩性复杂多样,保存了至少三个阶段的变质矿物组合。本文对其中的黑云斜长片麻岩和黑云二长片麻岩中的锆石,进行了详细的LA-ICP-MS U-Pb定年;对斜长角闪片麻岩中的变质角闪石,进行了常规40Ar/39Ar定年。定年结果表明:(1)黑云斜长片麻岩中的碎屑锆石记录了两期(~2.3Ga和~2.5Ga)明显的岩浆事件,变质锆石记录了一期(1.87~1.85Ga)变质事件;(2)黑云二长片麻岩中的岩浆锆石U-Pb年龄为2.33Ga和2.31Ga,变质锆石记录的变质年龄为1.96Ga;(3)两个斜长角闪片麻岩样品中,变质角闪石的40Ar/39Ar坪年龄和等时线年龄说明,该地区经历了一期~1.8Ga的变质热事件。这些数据说明,太华变质杂岩也记录了华北克拉通东部陆块与西部陆块之间的碰撞造山过程,不过比中部造山带其它变质杂岩区记录的时间更早,变质作用持续的时间也更长。这暗示了该地区在1.96~1.80Ga期间,经历了一次比较漫长而复杂的构造-变质演化过程。  相似文献   

Fault geometry as evidence for inversion of a former rift basin in the Eastern Lachlan Orogen     

D. R. Gray  R. T. Gregory 《Australian Journal of Earth Sciences》2013,60(4):513-523

Three major types of economic secondary iron ores occur in Western Australia, mainly in the banded iron-formation (BIF)-rich Hamersley Province of the Pilbara:

1. the dominant BIF-hosted bedded iron deposits (BID; ～40 billion tonnes (Bt); 58–65 wt% Fe); and the detrital ores, mainly in the three province-wide Cenozoic sequences that include coeval non-ore sediments:

2. Miocene channel iron deposits (CID; ～>15 Bt; 54–58 wt% Fe) of the Cenozoic Detritals 2 (CzD2); and

3. Eocene CzD1 and Pliocene CzD3 detrital iron deposits (DID; ～3.5 Bt; 40–60 wt% Fe).

Striking differences exist between the massive CID resources and the much smaller underlying and overlying DID. CID are essentially riverine alluvial ooidal rocks with abundant small fossil wood fragments and variable peloids, but with only extremely rare, recognisable lithic remnants. The original matrix is typically ramifying layered goethite. Eocene DID are mainly alluvial with only minor pisoids, whereas Pliocene–Quaternary DID are dominantly coarse colluvial gravels, with minor pisoids, both derived from and largely retaining the original textures of BID, hardcap or variably ferruginised surface BIF. The coluvial DID matrix is typically ferroan-aluminous soil, resulting in canga where replaced by goethite, which may be dehydrated to hematite in part by exposure. The Cenozoic deposits described in detail in this paper occur in two dominant geomorphological environments: the southern Marra Mamba to Brockman Iron Formation strike valleys (MBSV), containing all three Cenozoic sequences; and the much later northern Brockman IF plateau valleys (BPV) that include only the Miocene and Pliocene sequences. Minor basinal/deltaic alluvials occur in the Proterozoic. The Cenozoic detritals formed in different climatic regimes, with an extended dry period forming a prominent province-wide dehydrated carapace on the Eocene DID. The Miocene ‘optimum’ followed with its thick scrub-covered deep regolith that produced the fossil wood-rich CID, succeeded by the arid cool period of the Oakover limestone/calcrete. A major renewal of exposure and erosion in the Pliocene resulted in the extensive iron gravels of the Pliocene–Quaternary.  相似文献   

Stratigraphical evidence for the terrestrial age of australites     

J. F. Lovering  B. Mason  G. E. Williams  D. H. McColl 《Australian Journal of Earth Sciences》2013,60(4):409-418

Australites in an excellent state of preservation are common (up to 1 specimen per 300 m²) in lag gravels flooring corridors between seif dunes in the Motpena and Myrtle Springs areas of the Lake Torrens plain, South Australia. A study of the Quaternary stratigraphy of the region indicates that late Wisconsinan relict dunes (Lake Torrens Formation) are the most likely source of the australites. Radiocarbon dating indicates that the Lake Torrens Formation was deposited between about 24,000 and 16,000 years B.P. As the excellent preservation of most of the australites indicates that they have undergone negligible transport since their infall, it is concluded that the australites fell into the dune field sometime between about 24,000 and 16,000 years B.P.  相似文献   

The age of the lateritized summit surface on Kangaroo Island and adjacent areas of South Australia     

B. Daily  C. R. Twidale  A. R. Milnes 《Australian Journal of Earth Sciences》2013,60(4):387-392

Stratigraphic, geomorphological, and radiometric evidence shows that the laterite of the high plains and plateau of Kangaroo Island is older than the Middle Jurassic but younger than the Early Permian. Palaeoclimatic and palaeontological considerations suggest the Triassic as the most likely age of both the laterite and the surface on which it is developed. High‐level lateritized surfaces in the adjacent Mount Lofty Ranges and southern Eyre Peninsula are of similar age.  相似文献