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1.
The polymetallic Dushiling W-Cu deposit is a large, altered, skarn-type deposit, located in the northeastern part of the Miao'ershan-Yuechengling pluton, China. Two types of granite have been identified in the deposit: a medium-grained porphyritic biotite granite, and a medium- to fine-grained biotite granite. Both are spatially and temporally related to ore bodies, suggesting they may be the source of mineralization in the deposit. A medium- to fine-grained porphyritic biotite granite is exposed at the surface in the region of mineralization. U-Pb dating of zircons yielded magmatic ages of 423 Ma for the medium-grained porphyritic biotite granite and 421 Ma for the medium- to fine-grained porphyritic biotite granite, while a younger age(217 Ma) obtained for surface samples indicates later diagenesis. Thus, magmatism occurred during the Caledonian and Indosinian, respectively. The petrological and geochemical characteristics of the two Caledonian granites show that both are calc-alkaline and peraluminous.They are moderately enriched in Cs, Rb, U, and REE, and strongly depleted in Sr,Ba,P,and Ti; they show similar REE behavior,including negative Eu anomalies. These geochemical similarities suggest that the two granites were derived from the same source,although they were emplaced during different stages of the evolution of the magma. Furthermore, the granites are associated with mineralization, suggesting they were the source of mineralization in the Dushiling W-Cu deposit. Sm-Nd ages of scheelite from the Dushiling W-Cu deposit indicate that metallogenesis occurred at 417±35 Ma, while the two types of titanite, intergrown with scheelite, yield U-Pb ages of 423–425 Ma(in altered granite sample) and 218 Ma(in skarn sample). These ages place the main mineralization event in the late Caledonian, and later magmatic-hydrothermal activity occurred in the Indosinian. The ages obtained for the Dushiling W-Cu deposit in the western Nanling Range, northern Yuechengling, together with the occurrence and ages of the Niutangjie W deposit in southern Yuechengling, provide insight into the process of ore concentration during the Caledonian and Indosinian.  相似文献   

2.
The Zhuxi ore deposit is a super-large scheelite(copper) polymetallic deposit discovered in recent years. It grew above copper/tungsten-rich Neoproterozoic argilloarenaceous basement rocks and was formed in the contact zone between Yanshanian granites and Carboniferous-Permian limestone. Granites related to this mineralization mainly include equigranular, middle- to coarse-grained granites and granitic porphyries. There are two mineralization types: skarn scheelite(copper) and granite scheelite mineralization. The former is large scale and has a high content of scheelite, whereas the latter is small scale and has a low content of scheelite. In the Taqian-Fuchun Basin, its NW boundary is a thrust fault, and the SE boundary is an angular unconformity with Proterozoic basement. In Carboniferous-Permian rock assemblages, the tungsten and copper contents in the limestone are both very high. The contents of major elements in granitoids do not differ largely between the periphery and the inside of the Zhuxi ore deposit. In both areas, the values of the aluminum saturation index are A/CNK1.1, and the rocks are classified as potassium-rich strongly peraluminous granites. In terms of trace elements, compared to granites on the periphery of the Zhuxi ore deposit, the granites inside the Zhuxi ore deposit have smaller d Eu values, exhibit a significantly more negative Eu anomaly, are richer in Rb, U, Ta, Pb and Hf, and are more depleted in Ba, Ce, Sr, La and Ti, which indicates that they are highly differentiated S-type granites with a high degree of evolution. Under the influence of fluids, mineralization of sulfides is evident within massive rock formations inside the Zhuxi ore deposit, and the mean SO_3 content is 0.2%. Compared to peripheral rocks, the d Eu and total rare earth element(REE) content of granites inside the Zhuxi ore deposit are both lower, indicating a certain evolutionary inheritance relationship between the granites on the periphery and the granites inside the Zhuxi ore deposit. For peripheral and ore district plutons, U-Pb zircon dating shows an age range of 152–148 Ma. In situ Lu-Hf isotope analysis of zircon in the granites reveals that the calculated e_(Hf)(t) values are all negative, and the majority range from -6 to -9. The T_(DM2) values are concentrated in the range of 1.50–1.88 Ga(peak at 1.75 Ga), suggesting that the granitic magmas are derived from partial melting of ancient crust. This paper also discusses the metallogenic conditions and ore-controlling conditions of the ore district from the perspectives of mineral contents, hydrothermal alteration, and ore-controlling structures in the strata and the ore-bearing rocks. It is proposed that the Zhuxi ore deposit went through a multistage evolution, including oblique intrusion of granitic magmas, skarn mineralization, cooling and alteration, and precipitation of metal sulfides. The mineralization pattern can be summarized as "copper in the east and tungsten in the west, copper at shallow-middle depths and tungsten at deep depths, tungsten in the early stage and copper in the late stage".  相似文献   

3.
Precambrian basement rocks have been affected by Caledonian thermal metamorphism. Caledonian‐aged zircon grains from Precambrian basement rocks may have resulted from thermal metamorphism. However, Hercynian ages are rarely recorded. Zircon U–Pb Sensitive High Resolution Ion Microprobe (SHRIMP) dating reveals that zircon ages from the Huyan, Lingdou, and Pengkou granitic plutons can be divided into two groups: one group with ages of 398.9 ±5.3 Ma, 399 ±5 Ma, and 410.2 ±5.4 Ma; and a second group with ages of 354 ±11 Ma, 364.6 ±6.7 Ma, and 368 ±14 Ma. The group of zircon U–Pb ages dated at 410–400 Ma represent Caledonian magmatism, whereas the 368–354 Ma ages represent the age of deformation, which produced gneissosity. The three plutons share geochemical characteristics with S‐type granites and belong to the high‐K calc‐alkaline series of peraluminous rocks. They have (87Sr/86Sr)i ratios of 0.710 45–0.724 68 and εNd(t) values of ?7.33 to ?10.74, with two‐stage Nd model ages (TDM2) ranging from 1.84 Ga to 2.10 Ga. Magmatic zircon εHf(t) values range from ?3.79 to ?8.44, and have TDMC ages of 1.65–1.93 Ga. The data suggest that these granites formed by partial melting of Paleoproterozoic to Mesoproterozoic continental crust. A collision occurred between the Wuyi and Minyue microcontinents within the Cathaysia Block and formed S‐type granite in the southwest Fujian province. The ca 360 Ma zircon U–Pb ages can represent a newly recognized period of deformation which coincided with the formation of the unified Cathaysia Block.  相似文献   

4.
The samples from the hidden Daqiling muscovite monzonite granite, which has recently been recognized within the Limu Sn-polymetallic ore field, have been analyzed for zircon U-Pb ages and whole rock geochemical and Nd-Hf isotopic compositions to discuss its genesis, source, and tectonic setting. LA-ICP-MS zircon U-Pb dating indicates that the granite crystallized in the late Indosinian (224.8±1.6 Ma). The granite is enriched in SiO2 and K2O and low in CaO and Na2O. It is strongly peraluminous with the A/CNK values of 1.09–1.20 and 1.4 vol%–2.7 vol% normal corundum. Chondrite-normalized REE patterns show slightly right-dipping shape with strongly negative Eu anomalies (δEu =0.08–0.17). All samples show enrichment of LILEs (Cs, Rb and K) and HFSEs (U, Pb, Ce and Hf), but have relatively low contents of Ba, Sr and Ti. The zircon saturation temperatures (T zr) are from 711 to 740°C, which are slightly lower than the average value of typical S-type granite (764°C). The granite has negative ? Nd(t) and ? Hf(t) values, which change from ?9.1 to ?10.1 with the peak values of ?9.2 to ?9.0 and from ?3.7 to ?12.6 with the peak values of ?6 to ?5, respectively. The T DM C (Nd) and T DM C (Hf) values are 1.74–1.82 Ga with the peak values of 1.73–1.75 Ga and 1.49–2.04 Ga with the peak values of 1.5–1.6 Ga, respectively. These characteristics reveal that the source region of the granite is dominantly late Paleoproterozoic to early Mesoproterozoic crustal materials. Seven inherited magmatic zircons are dated at the age of 248.6±4.3 Ma, which suggests the existence of the early Indosinian granite in Limu area. These zircons have the ? Hf(t) values of ?6.7–?2.3, similar to those of the Daqiling granite, implying the involvement of the early Indosinian granite during the formation of the Daqiling granite. Inherited zircon of 945±11 Ma has the ? Hf(t) and T DM(Hf) values of 8.7 and 1.14 Ga, respectively, compatible with those of the Neoproterozoic arc magmatic rocks in the eastern Jiangnan orogenic belt. Therefore we inferred that Neoproterozoic arc magma might have been involved in the formation of the Daqiling granite, and that the Neoproterozoic arc magma belt and continent-arc collision belt between the Yangtze and Cathaysia Blocks might have extended westsouthward to Limu region. It is proposed that the underplating of mantle materials triggered by crustal extension and thinning resulted in partial melting of crustal materials to form the Daqiling granite in the late Indosinian under post-collisional tectonic setting.  相似文献   

5.
The large-scale Huangshaping Pb-Zn-W-Mo polymetallic deposit is located in the central Nanling min- eralization zone, South China. Six molybdenite samples from the Huangshaping deposit were selected for Re-Os isotope measurement in order to define the mineralization age of the deposit. It yields a Re-Os isochron age of 154.8±1.9 Ma (2σ ), which is in accordance with the Re-Os model ages of 150.9― 156.9 Ma. This age is about 7 Ma younger than their host granite porphyry, which was dated as 161.6±1.1 Ma by zircon U-Pb method using LA-ICPMS. All these ages demonstrate that the Huang- shaping granite and related Pb-Zn-W-Mo deposit occurred in the middle Yanshanian period, when many other granitoid and related ore deposits emplaced and formed, e.g. the Qitianling granite and Furong tin deposit, the Qianlishan granite and giant Shizhuyuan W-Sn-Mo-Bi deposit and Jinchuantang Sn-Bi deposit in the nearby area. They constitute the main part of the magmatic-metallogenic belt of southern Hunan, and represent the large-scale metallogeny in middle Yanshanian in the area. The lower rhenium content in molybdenite of Huangshaping deposit suggests that the ore-forming material was mainly of crust origin.  相似文献   

6.
The Nanling metallogenic belt in South China is characterized by well-developed tungsten-tin mineralization related to multiple-aged granitoids. This belt is one of the 5 key prospecting and exploration areas among the 19 important metallogenic targets in China. Important progress has been made in recent years in understanding the Nanling granitoids and associated mineralization, and this paper introduces the latest major findings as follows: (1) there exists a series of Caledonian, Indosinian, and Yanshanian W-Sn-bearing granites; (2) the Sn-bearing Yanshanian granites in the Nanling Range form an NE-SW trending aluminous A-type granite belt that stretches over 350 km. The granites typically belong to the magnetite series, and dioritic micro-granular enclaves with mingling features are very common; (3) the Early Yanshanian Sn- and W-bearing granites possess different petrological and geochemical features to each other: most Sn-bearing granites are metaluminous to weakly peraluminous biotite (hornblende) granites, with zircon ?Hf(t) values of ca. ?2 to ?8, whereas most W-bearing granites are peraluminous two-mica granites or muscovite granites with ?Hf(t) values of ca. ?8 to ?12; (4) based on the petrology and geochemistry of the W-Sn-bearing granites, mineralogical studies have shown that common minerals such as titanite, magnetite, and biotite may be used as indicators for discriminating the mineralizing potential of the Sn-bearing granites. Similarly, W-bearing minerals such as wolframite may indicate the mineralizing potential of the W-bearing granites. Future studies should be focused on examining the internal relationships between the multiple-aged granites in composite bodies, the metallogenic peculiarities of multiple-aged W-Sn-bearing granites, the links between melt evolution and highly evolved ore-bearing felsic dykes, and the connections between granite domes and mineralization.  相似文献   

7.
The Nanling Mountains lying in the southern part of South China are an economically important gran-ite-related multi-metallogenic province. The Nanling Mountains granites can be described as: temporally spanning from Caledonian to Yanshanian and spatially distributed as three EW trending zones: the north one in Zhuguangshan-Qingzhangshan, the middle one in Dadongshan-Guidong, and the south one in Fogang-Xinfengjiang with two neighboring zones’ midline having an interval of ca. latitude …  相似文献   

8.
Nd and Sr isotope determinations on late Precambrian to early Palaeozoic igneous and sedimentary rocks from the Arabian Shield are used to investigate the proportion of reworked “older” crust, and the rate at which new crust was generated during the Pan African event. Eight Rb/Sr whole rock isochrons on igneous suites yield ages in the range 770?590 Ma and initial 87Sr/86Sr ratios of 0.7038?0.7023. These data confirm that magmatism in this area was largely restricted to the period 850-550 Ma, and the initial ratios are sufficiently low to preclude significant contributions from a long-lived upper crustal source. The initial 143Nd/144Nd ratios of a variety of lithologies, including several samples of possible “basement”, are all higher than the contemporaneous values for CHUR (εNd = +1.6 to +6.9), suggesting that many were derived directly from the upper mantle, and that any inferred crustal source regions for the remainder could not have separated from likely LREE-depleted mantle reservoirs before 1200 Ma. The Arabian Shield therefore provides an example of rapid crustal growth during the Late Proterozoic, and contrasts with the Damara intracratonic belt of Namibia where Nd and Sr isotopes provide strong evidence for extensive reworking of older continental crust during the same period.  相似文献   

9.
The Nyainqêntanglha Group is traditionally viewed as the oldest metamorphic basement in the Lhasa block, but its formation age and tectonic setting remain debate. Zircons extracted from the metamorphic sequence of volcanics and intrusions of the Nyainqêntanglha Group, 10 km west of Nam Co in northern Lhasa block, have been investigated by cathodoluminescence (CL), backscattered (BSE) and dated by ion microprobe (SHRIMP). We conclude that the U-Pb age of 787 ê9 Ma of zircons from the trondhjemite imposes a constraint on maxi-mum protolith age, and minimum formation age of the Nyainqêntanglha Group is constrained by U-Pb age of 748 ê8 Ma of zircons from the granite. The formation age of the Nyainqêntanglha Group is consistent with sedimentary age of Greater Himalayan rocks, showing that they devel-oped coevally in an arc-basin tectonic setting of Neoproterozoic active continental margin along the northern margin of the India shield. The inherited zircons from the tholetiite and granite give older 207 Pb/206 Pb ages from 947 to 1766 Ma. The positive å Nd(t) value indicates that the mafic rocks were derived from the depleted mantle, but contaminated by the older continental crustal material. Integrated Nd model age and U-Pb age data provide excellent evidence for the existence of Mesoproterozoic basement in the Lhasa block during Neoproterozoic time.  相似文献   

10.
简介了江西崇义淘锡坑大型钨矿床的地质背景、矿化特征,详细叙述了淘锡坑岩体的形态、分布、矿物成分、化学成分,归纳了最新的同位素年龄及地球化学数据,探讨了淘锡坑岩体作为成矿母岩的成矿作用,并对其整体形态进行了预测,分析了下步的找矿有利地段。  相似文献   

11.
This paper summarizes the geochronological, geochemical and zircon Hf isotopic data for Mesozoic granitoids within the Erguna Massif, NE China, and discusses the spatial-temporal variation of zircon Hf isotopic compositions, with the aim of constraining the accretion and reworking processes of continental crust within the Erguna Massif, and shedding light on the crustal evolution of the eastern segment of the Central Asian Orogenic Belt. Based on the zircon U-Pb dating results, the Mesozoic granitic magmatisms within the Erguna Massif can be subdivided into five stages: Early-Middle Triassic(249–237 Ma), Late Triassic(229–201 Ma), Early-Middle Jurassic(199–171 Ma), Late Jurassic(155–149 Ma), and Early Cretaceous(145–125 Ma).The Triassic to Early-Middle Jurassic granitoids are mainly I-type granites and minor adakitic rocks, whereas the Late Jurassic to Early Cretaceous granitoids are mainly A-type granites. This change in magmatism is consistent with the southward subduction of the Mongol-Okhotsk oceanic plate and subsequent collision and crustal thickening, followed by post-collision extension. Zircon Hf isotopic data indicate that crustal accretion of the Erguna Massif occurred in the Mesoproterozoic and Neoproterozoic. ZirconεHf(t) values increase gradually over time, whereas two-stage model(TDM2) ages decrease throughout the Mesozoic. The latter result indicates a change in the source of granitic magmas from the melting of ancient crust to more juvenile crust. Zircon εHf(t)values also exhibit spatial variations, with values decreasing northwards, whereas TDM2 ages increase. This pattern suggests that,moving from south to north, there is an increasing component of ancient crustal material within the lower continental crust of the Erguna Massif. Even if at the same latitude, the zircon Hf isotopic compositions are also inconsistent. These results reveal lateral and vertical heterogeneities in the lower continental crust of the Erguna Massif during the Mesozoic, which we use as the basis of a structural and tectonic model for this region.  相似文献   

12.
Relict high-pressure granulite-facies rocks have been found in the Ami?tsoq gneisses and inclusions of the older Akilia supracrustal association, on islands south of Godthåb. Only amphibolite-facies assemblages have been found in Ameralik dykes and younger rocks from this area. The Ami?tsoq gneisses are depleted in Rb and U relative to those of Ameralik and Isua. Well-fitted Pb/Pb and Rb-Sr isochrons on Ami?tsoq granulites indicate that this depletion, correlated with the granulite-facies metamorphism, occurred ca. 3600 Ma ago. Textural features suggest that the present cpx + opc + gnt + plag + qtz + hbl assemblages evolved from earlierintermediate-P assemblages (cpx + opx + plag), probably during cooling from the metamorphic peak. Re-equilibrium of olderintermediate-P assemblages in local environments of low ?H2O, during the ca. 2800-Ma metamorphism of the Malene supracrustals, is feasible but is considered unlikely. Either interpretation requires crustal thickness of at least 20 km and geothermal gradients of?30°C/km, ca.3600Ma ago. The higher heat production of early Archaean times was apparently dissipated through oceanic, rather than continental, areas.  相似文献   

13.
The subduction of “hot” Shikoku Basin and the mantle upwelling related to the Japan Sea opening have induced extensive magmatism during the middle Miocene on both the back-arc and island-arc sides of southwest Japan. The Goto Islands are located on the back-arc side of northwestern Kyushu, and middle Miocene granitic rocks and associated volcanic, hypabyssal, and gabbroic rocks are exposed. The igneous rocks at Tannayama on Nakadori-jima in the Goto Islands consist of gabbronorite, granite, granite porphyry, diorite porphyry, andesite, and rhyolite. We performed detailed geological mapping at a 1:10 000 scale, as well as petrographical and geochemical analyses. We also determined the zircon U–Pb age dating of the igneous rocks from Tannayama together with a granitic rock in Yagatamesaki. The zircon U–Pb ages of the Tannayama igneous rocks show the crystallization ages of 14.7 Ma ± 0.3 Ma (gabbronorite), 15.9 Ma ± 0.5 Ma (granite), 15.4 Ma ± 0.9 Ma (granite porphyry), and 15.1 Ma ± 2.1 Ma (rhyolite). Zircons from the Yagatamesaki granitic rock yield 14.5 Ma ± 0.7 Ma. Considering field relationships, new zircon data indicate that the Tannayama granite formed at ~16–15 Ma, and the gabbronorite, granite porphyry, diorite porphyry, andesite, and subsequently rhyolite formed at 15–14 Ma, which overlaps a plutonic activity of the Yagatamesaki. The geochemical characteristics of the Tannayama igneous rocks are similar to those of the tholeiitic basalts and dacites of Hirado, and the granitic rocks of Tsushima in northwestern Kyushu. This suggests that the Tannayama igneous rocks can be correlated petrogenetically with the igneous rocks in those areas, with all of them generated by the upwelling of hot mantle diapirs during crustal thinning in an extensional environment during the middle Miocene.  相似文献   

14.
Granulite facies metamorphism and crustal anatexis exist in the East Cathaysia Block, the exact timing of granulite facies partial melting and its link with orogenesis have not been well constrained. In this study, we carried out petrography, whole rock geochemistry, and zircon U–Pb dating, trace elements and Hf isotopes analyses on Dazhe gneissic granite and banded migmatite from the Badu Group in southwest Zhejiang province in the East Cathaysia Block. The melts were produced through the dehydration of biotite, such as biotite + quartz + plagioclase = orthopyroxene + K-feldspar + melt and biotite + quartz + plagioclase + sillimanite = garnet + K-feldspar + melt. Zircons from these rocks show clear core-rim structure and yield rim and core concordant ages at 233 Ma and 1.83 Ga, respectively. The zircon rims suggesting the melts and the cores are suggesting the protolith of Dazhe gneissic granite and banded migmatite were crystallized from an evolving magma. The zircon cores and rims have negative εHf(t) = −2.2 ~ −6.3 and εHf(t) = −22.8 ~ −32.4, and they give suggestion of the presence of Neoarchean components. Although the major-element compositions of the gneissic granite and banded migmatite are slightly different, the trace-element spider diagram and REE pattern show they are similar, and then we find that the protoliths are A-type granodiorite/diorite. Combined with the published data, we suggested that the Dazhe gneissic granite and banded migmatite were formed through granulite facies partial melting at 233 Ma, which was promoted by crustal shortening and thickening of the collision orogeny between East Cathaysia Block and an unknown terrane with a NNE trend structure line. The protoliths (granite or granodiorite) of Dazhe gneissic granite and banded migmatite crystallized at 1.83 Ga by reworking of the Neoarchean components of East Cathaysia Block. The Paleoproterozoic (1912–1819 Ma) collisional orogeny and the later intraplate rifting stage are corresponding to the aggregation and breakup of the Columbia supercontinent.  相似文献   

15.
Carbonatites are rarely igneous rocks distributed on the earth. The rocks usually form ring complexes with alkalic rocks, occurring in the environments of continental rift, collisional oro-genic zone and oceanic island[1, 2]. Numerous facts and experiment…  相似文献   

16.
The Queershan composite granitic pluton is located in the north of the late Paleozoic Yidun arc collision-orogenic belt, eastern Tibetan Plateau. The main rock types are coarse-grained porphyritic alkalic-monzonite granite with minor fine-grained porphyritic monzogranite and granodiorite distributed in the eastern and southwestern regions. Here we report their zircon U-Pb ages and geo- chemical data. The intrusive contact relations indicate that granodiorite was formed earlier than the alkalic-monzonite granite(105.9±1.3 Ma) and monzogranite(102.6±1.1 Ma). These suggest that the Queershan composite granitic pluton was formed through three-stage magmatic events. The alkalic-monzonite granite(105.9±1.3 Ma) and monzogranite(102.6±1.1 Ma) are characterized by high SiO2(73.5%–77.7%), K2O+Na2O(6.9%–8.5%), Ga/Al ratios(2.6–3.4) and low Al2O3(11.8%–14.5%), CaO(0.25%–1.5%), MgO(0.18%–0.69%), negative Ba, Sr and Eu anomalies, showing A-type granite affinities. The granodiorite exhibits lower SiO2, P2O5 and K2O+Na2O contents, but higher Al2O3, CaO and MgO contents than alkalic-monzonite granite and monzogranite, showing I-type granite affinity. 176Hf/177 Hf ratios of the alkalic-monzonite granite and the monzogranite are 0.282692–0.282749 and 0.282685–0.282765, respectively, and with similar ?Hf(t) values(?0.56 to 1.43 and ?0.87 to 1.90 respectively). They also present similar TDM2 model ages(1.04–1.22 and 1.07–1.2 Ga respectively), indicating they may be sourced from a similar rock source, mostly like Kangding Complex. The homogeneity of the Hf isotopic compositions and the absence of the MMEs demonstrate that little depleted mantle materials have contributed to the source. We propose that the Mesoproterozoic crust materials of the Yangtze Craton exist beneath the Yidun arc terrane and support it was a dismembered part of the Yangtze Craton. The A-type granites of Queershan composite granitic pluton are most probably related to the closure of the Bangong-Nujiang Tethys ocean.  相似文献   

17.
The petrographic characteristics of Jingshan "migmatitic granite" and the occurrence of the magmatic zircons indicate that the granite was formed by normal crystallization of felsic melts. All zircons in the granite have inherited cores and fine-scale oscillatory zoning rims of magmatic origin. It is realized that the granite was formed at 160.2±1.3 Ma through dating magmatic zircons. The generation of the granitic magma could be related to the lithospheric mantle and/or lower crust delamination after the ultrahigh pressure metamorphism (UHPM) in Triassic. Most inherited zircons yield the ages of 217.1±6.6 Ma, which is consistent with the peak UHPM in the Dabie-Sulu orogenic belt. Some of the inherited zircons (433-722 Ma) constitute a discordia line with the upper intercept age of 850+85/-68 Ma and a lower intercept age of 261+100/-140 Ma. These ages imply that the granite could be derived from the partial melting of the crustal materials of the South China Block that was intensively superimposed by t  相似文献   

18.
江西省大湖塘石门寺矿区超大型钨矿的发现及找矿意义   总被引：4，自引：0，他引：4  
江西省武宁县大湖塘石门寺超大型钨矿的成功勘查是我国地质找矿工作的重大发现。矿化类型划分为细脉浸染型、隐爆角砾岩型和石英大脉型。前者占总储量的74％,该类型以晋宁晚期黑云母花岗闪长岩为容矿围岩,以燕山中期酸性深成至浅成花岗岩为成矿母岩。矿体厚大且产状平缓,大致平行于黑云母花岗闪长岩与似斑状黑云母花岗岩株顶部的接触面分布,以外接触带为主（I1矿体）,水平投影面积1．50km2,单工程最大厚度389．33m,平均厚度143．67m,平均品位0．193％,厚度变化系数63．7％,品位变化系数115．8％。工业矿物主要为白钨矿、黑钨矿、黄铜矿、辉钼矿。矿石组构类型主要有结晶结构、交代结构、细脉状构造、浸染状构造,常见近矿围岩蚀变为黑鳞云母化、云英岩化、绿泥石化,成因类型属岩浆期后高中温热液矿床,工业类型可划归为细脉浸染型白钨矿。石门寺矿区以黑云母花岗闪长岩为容矿围岩的细脉浸染状白钨的发现,改变了以往只专注评价石英大脉型黑钨矿的找矿思路,为矿区及九岭矿集区实现钨多金属找矿突破指明了新的方向。  相似文献   

19.
Abstract In northern Kazakhstan the WNW striking Kokchetav megamélange includes different crustal sequences with high‐pressure/ultrahigh‐pressure (HP/UHP) remnants of their 540–520 Ma subduction metamorphism. Two domains separated by the north‐east trending Chaglinka fault are distinguished. The western domain exhibits NE–SW structures within a single Kumdy–Kol megaunit of diamond‐bearing UHP metasediments and high‐temperature (HT) eclogites. The eastern domain consists of the composite Kulet megaunit with the Kulet UHP unit (coesite‐bearing metasediments, whiteschists and eclogites), the Enbek–Berlyk medium‐pressure (MP) unit (kyanite‐bearing, high‐alumina rocks with interleaved coronitic metagabbro), and ortho‐ and paragneisses with eclogites and amphibolites included. All eclogites in the eastern domain are of the relatively low temperature (LT) type. Sillimanite is common and appears after kyanite in the sheared MP unit. A regional and moderately ESE plunging linear fabric coincides with the fold‐axis of the foliation poles from the eastern domain. Whether this also reflects a regional top to the WNW transport, as inferred from the dextral strike‐slip on steeply to SSW dipping foliation, needs further study. Top to the WNW shear is shown by weakly inclined low pressure (LP) cordierite rocks that flank the eastern domain in the south. Some new 39Ar/40Ar mica cooling ages (519, 521 Ma) from the Kulet UHP micaschists reflect the same early stage evolutionary event as was previously shown for the Kumdy–Kol UHP rocks (515, 517 Ma) in the west. Similar 39Ar/40Ar ages (500, 517 Ma) are recorded by micas and amphibole that outline a top to NNW shear fabric in the non‐subducted Proterozoic basement, north of the megamélange. A 447 Ma overprint of the MP sequences is considered to reflect the strike‐slip deformation with sillimanite and the reworking of an early kyanite‐bearing tectonite. Biotites from the LP cordierite rocks yielded approximately 400 Ma 39Ar/40Ar ages. In case they reflect the WNW shear deformation, the latter is considered to be associated with a regional granite magmatism (420–460 Ma) extending south of the eastern domain. In their present different structural domains the Kulet and Kumdy–Kol UHP units display a similar early stage event. Subsequent LP deformation, which is likely to be associated with regional granite magmatism (420–460 Ma), is assumed to have obliterated any common or uniform early exhumation structure for the whole megamélange. The north‐east structured Kumdy–Kol domain is assumed to have preserved the most information about the early stage exhumation. This domain is at an angle to the regional WNW strike of the megamélange.  相似文献   

20.
The Indosinian Orogeny plays a significant role in tectonic background and magmatic evolution in Indochina and surrounding regions. Being a part product of the Indosinian magmatism in northwest Vietnam during late Permian–middle Triassic period, Muong Luan granitoid pluton dominantly consists of granodiorite, less diorite and granite. This pluton is located in the Song Ma suture and assigned to the Dien Bien complex. Geochemically, the Muong Luan granitoid rocks are characterized by a wide range of SiO2 contents (59.9–75.1 wt%) and high K2O contents. They display typical features of I‐type granites. The presence of hornblende and no muscovite and cordierite in the rocks further supports for I‐type character of granitoids. The emplacement age of the Muong Luan pluton obtained by LA–ICP–MS U–Pb zircon is at 242–235 Ma, corresponding to Indosinian time. Zircon εHf values of –5.6 to –10.4, in combination with moderate Mg values of 34–45 suggested that the Muong Luan granitoid was derived from partial melting of mafic crustal source rocks, which are probably Paleoproterozoic in age as revealed by Hf model ages (TDM2 = 1624–1923 Ma).  相似文献   

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