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Judge tells mom: Don’t breastfeed in courtroom
posted: November 10,
“I felt like I was being attacked for breastfeeding.”
So says Michigan mom Natalie Hegedus, who claims that she was left “humiliated” this week when a district court judge openly admonished her for breastfeeding her 5-month-old baby in the courthouse.
Natalie hadn’t planned on bringing her son Landon with her when she went to court this past Tuesday, but had to pull him out of daycare after he came down with an ear infection. So when he became hungry after a 2-hour wait, she did what most moms would do – she fed him.
Making sure that “nothing was showing,” Natalie says that she discretely nursed Landon as she continued to wait in the courtroom. When her name was finally called, she asked the Honorable Robert T. Hentchel for a moment as she collected herself and her son. According to Natalie, the judge then asked her if she thought the courtroom was an appropriate place to breastfeed her baby.
Showing considerable calm, Natalie says that she pointed out that her son was hungry and that nursing in public is not against the law so she didn’t feel it was inappopriate to feed him there. She claims that the judge disagreed, citing, “My court, my law and I feel it is.” Apparently it was then that the mortified mom noticed a note that a court employee had passed to the bench that warned, “There is a woman breastfeeding in court.”
“Needless to say I left in tears, I have never felt so humiliated,” Natalie wrote as she later related the experience in a post in the . She was so outraged that she’s contacted lawyers and plans on filing a formal complaint.
As disappointing as Natalie’s story is, what makes it all the more frustrating is the fact that it’s not exactly a one-off incident. She is just one of many moms who have felt judged and criticized for simply feeding their children. Despite the fact that just about everybody encourages moms to breastfeed these days, we still hear stories of women being ,
for daring to nurse their babies in public.
Is it any wonder that new moms like BabyCenter blogger
might have a few jitters at the prospect of breastfeeding in public?
If we really want to encourage nursing, then it can’t be shrouded in mystery and shielded from sight, something that good moms do while huddled behind closed nursery doors. Natalie’s story just goes to show that despite all of our best intentions, society’s collective hang-up over breastfeeding still exists.
What do you think of Natalie’s story? And of breastfeeding in public?
Photo: Flickr ()
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Latest in Tips & Tricks364Vol. 75 No. 4ACTA GEOLOGICA SINICADec. 2001A Study of the Kunlun-Qilian-QinlingSuture SystemBIAN Qiantao&#39;, GAO Shanlin&#39;, LI Dihui2,YE Zhengren&#39;, CHANG Chengfa&#39;, LUO Xiaoquan&#39; 1 Institute of Geology and Geophysics,
Chinese Academy of Sciences, Beijing
Science Press, Chinese Academy of Sciences, Beijing I &I71 7Abstract The Late Neoproterozoic-Early Palaeozoic suture zones within the Central Orogenic Belt of China can be considered a system-the Kunlun-Qilian-Qinling suture system (KQQ suture system). It is basically divided into the western, central and eastern sectors. The western sector consists of the KUda-Subashi suture zone, the MazarKangxiwar suture and the central West Kunlun microblock. The cenbal sector covers the following five suture zones: the Altun,North Qilian, Qaidam northern marginal, Qimantag-Wutuo and East Kunlun southern marginal sutures, in addition to some microblocks such as the mid-south Qilian. Qaidam. Ayakkum and Maqen microblocks. The eastern sector is composed of the Shangdan suture zone, Mianlile suture zone and central Qinling-Dabie microblock. The KQQ suture system experienced (1) extending-rifting of the Rodinia supercontinent in the early-middle Sinian (-78(Moo Ma); (2) the formation and evolution of the KQQ archipelagic ocean during the Late Sinian-ordovician (-600-440 Ma), and (3) closing of the KQQ Ocean and forming of the KQQ suture system during the Late Ordovician-early Silurian (-440400 Ma). As a system comprising many suture zones and microblocks. the KQQ suture system constitutes the foundation of the Central Orogenic Belt of China. 1 Tectonic Location and Construction of the KQQ Suture SystemAs the principal part of the Central Orogenic Belt of China, the well-known Kunlun, Qilian and Qinling (KQQ) orogenic belts can be regarded as a unifying orogenic belt in terms of tectonics (Wang et al., 1995; Xiao et al., 1995; Xu et al., 1996;Zhang et al., 1998; Y m et al., 1998). A number of late Sinian-early Palaeozoic suture zones and microblocks are widely distributed in the KQQ suture system. Based on the researches of previous geologists as well as the authors, an attempt is made in this paper to unite those suture zones and microblocks surrounded by the suture zones as a system, o study their formation, evolution and and further t tectonic significance and their relationships.1.2 Construction of the KQQ suture system The KQQ suture system can be generally divided into three sectors: the west sector, equivalent to the west K the bulky and complicated middle sector, covering approximately the north Qilian, east Kunlun and Altun (Altyn) orogenic belts and e and the east sector, analogous approximately to the Qinling orogenic belt (Fig. 1).1.2.1 The west sector of the KQQ suture system The west sector of the KQQ suture system is composed of the Kiida-Subashi and Mazar-Kangxiwar sutures and central West Kunlun microblock. The two sutures are connected with the AItun suture, Qimantag-Wutuo suture and East Kunlun southern marginal suture in the east and stretch in a WNW direction into the northern Pamirs in the west. There is a suture knot, the AltunKunlun suture knot as named by the authors, at the intersection of the Altun Mountains and the Kunlun Mountains. The Kiida-Subashi suture is more than 1000 km long and a few or more than ten km wide. Dismembered ophiolites outcrop along the suture, including the Wuyitage, Kegang, KUda, Subashi and Arpa ohiolites. Taking the KUda ophiolite as an example, the rock units are dominated by metaperidotite, diabase dykes, pillow1.1 Tectonic location The KQQ suture system i s located in central China. It borders the Tarim and North China blocks on the north and adjoins the Palaeotethyan suture system on the south (Bian et al., 1997), extending westerly through the Pamirs and west lianshan to the Sudetian orogenic belt in Europe and easterly through Wulian and Rongcheng in Shandong Province to Korea, being cut off by the Tanlu Fault (Jiang et al., 2000).Vol. 75 No.4ACTA GEOLOGICA SINICADec.2001365Fig. 1. A sketch map showing the structure and tectonic setting of the Kunlun-Qilian-Qinling suture system.Ophiolites: 1,Wuyitage: 2. Kegang: 3. KUda 4. Subashi: 5. Arpa 6. Hongliugou: 7. T 8. Mangnai: 9. south of the Altun peak: 10. Dangjin M o u n t a i n Pas3 1 1 . Dadaorji 12. Jiugequan 13. Dachadaban 14. Bianmagou 15. Yushigou 16. Laohushan 17. Honggou 18. Lajishan 19. Wusushan 20. Sertengshan 21. LUliangshan: 22. Xitiahan: 23. Chakananshm 24. Qimantag 25. Sanchako~~ 26. Wutua 27. Qingshuiquan: 28. Zanahem 29. Mu~tag 30. H 31. Buqingshan: 32. Tatu: 33, Xia Dawo: 34. Majixueshan: 35. Dur&#39;ngoi: 36. Yuanyangzhen 37. Yanwan: 38. Sujiahe: 39. Sifangtai: 40.Songshugou: 41. Erlangping: 42. Tongbbaidahe: 43. Raobozhai: 44. MianlUe: 45. Zhoujiawan. Suture zones: U S - KUda-S MKS - Mazar-KALS A NQS - North Q QNS - Qai QWS - QiaantagW EKSS - East Kunl SDS - S MLS.MianlUe. Microblocks: WK - central West K MSQ - mid-south Q QDM - Q AK - Ayakkum: MQ - M W-D - Central Qinling-Dabie.-basalt, massive basalt and siliceous rocks and the metaperidotite shows clearly plastic rheological fabrics in a high-temperature environment of the upper mantle (Bian et al., 1995). Most of the geologists believe that the ophiolites were formed in the late Neoproterozoic-early Early Palaeozoic period (Xu et al., 1994; Deng, 1995; Ding et al., 1996), while a few argue that they were formed in the late Palaeozoic (Jiang et al., 1992; Yang et al., 1996). The Kiida-Subashi ophiolite belt, however, is probably a composite ophiolite belt composed of Neoproterozoic-early Early Palaeozoic and late Palaeozoic ophiolites. The siliceous flysh in the Kiida ophiolite belongs to deep-sea ophiolite-related turbidites (Wang et al., 1989). Based on the discovered MORB, IAB, CAB and vitric andesite in the Kiida ophiolite, many researchers think that the Kuda ophiolite was formed in a supra-subduction zone (SSZ) (Jiang et al., 1992; Deng, 1995; Yang et al., 1996; Zhang and Zhou, 2000). Calc-alkaline granites of two stages, 400-450 Ma and 200-270 Ma, are developed in the central West Kunlun micrblock, which means a superposition of two-stage island-arcs: the Caledonianand Hercynian. No ophiolites have been found yet in the MazarKangxiwar suture. It is considered a suture in view of two facts: (1) on its north side there are distributed island-arc belts of two stages, the Caledonian and Hercynian-Lndosinian, and the Wu yitage-Kiida-Subashi SSZtype ophiolite belt, which is characterized by strong deformation and Caledonian folds (Jiang et al., 2000); and (2) the strata on its two sides have distinct stratigraphic, magmatic, tectonic deformation and metamorphic features. Furthermore, it also stretches eastwards to join the Altun-Kunlun knot.1.2.2 The central sector of the KQQ suture system The central sector of the KQQ suture system has the following structural pattern: the North Qilian suture, Altun suture and Qaidam northern marginal suture surround the south-central Q the Altun suture, Qaidam northern marginal suture and QimantagWutuo suture circle the Q and the Qimantag-Wutuo and East Kunlun southern marginal sutures sandwich the Ayakkum and Maqen microblocks.366Study of the Kunlun-Qilian-Qinling Suture SystemBian et al.Moreover, a number of small microblocks are sandwiched within the North Qilian and Altun sutures.(1) The Altun suture zone The Altun suture zone includes the HongliugouLapeiquan ophiolitic mClange in the north and the ArpaMangnai ophiolitic mClange in the south, as well as the Milanhe-Jinyanshan microblock in between (Cui et al., 1999; Wang et al., 1999). The Hongliugou-Lapeiquan ophiolitic mClange is composed of metaperidotite, cumulate gabbro, diabase, basalts, siliceous rocks etc. Its Sm-Nd isochronal age is 508k41.4 Ma (Liu, 1999). The basalts are mainly the MORB and secondarily the IAB. The HongliugouLapeiquan ophiolitic mClange is comparable with those in North Qilian, and they probably resulted from the same ocean basin. The complex stretches westwards beneath thick Mesozoic-Cenozoic sediments. Magnetic data seem to show that it turns sharply to the southwest after crossing the Qiemo-Heijianshan fault and tends to join the early-Palaeozoic West Kunlun ophiolitic mClange (Cui et al., 1999). The Arpa-Mangnai ophiolitic mClange starts from southern and eastern Yutian County and stretches eastwards to the Dangjin Mountain Pass. The ophiolitic mClange consists of ophiolites in Arpa, &Ma, Mangnai, the Dangjin Mountain Pass and the south of the Altun Peak. The ophiolites are composed dominantly of ultramafte and epimetamorphic basic volcanic rocks including mantle peridotite associated with small amounts of gabbros, andesites and siliceous rocks. The Sm-Nd isochronal age of the basic volcanic rocks is 481.3k53 Ma (Liu et al., 1998). The mantle peridotite consists mainly of depleted harzburgite and dunite, and the basalt is mainly the E-MORB formed in ocean ridges (Wang et al., 1999).(2) The North Qilian suture zone The North Qilian suture is sandwiched between the Alxa and south-central Qilian blocks, and westerly joins the Altun suture and easterly with the Shangdan suture zone in the North Qinling region. This suture zone includes four ophiolite belts from&#39;south to north (Feng et al., 1996; Xia et al., 1996; Zhang and Zhou. 2000) as follows. The Yushigou ophiolite belt, including the Chuancigou and Xiaobabao ophiolites in the east, is composed primarily of metaperidotite (mainly harzburgite),cumulate gabbro, homogeneous gabbro, pillow basalt, plagiogranite and radiolarian siliceous rocks. The basalt has MORB characteristics (Feng et al., 1995) and a SmNd isochronal age of 522-495 Ma (Xia et al., 1996). The Late Cambrian-Early Ordovician fossils discovered in interbedded radiolarian chert indicate that the ophiolite was formed in the Cambrian-Early Ordovician (Feng et al., 1996a). The Bianmagou ophiolite belt connects easterly with the Qingshuiquan and Baijingsi blueschist belts and is part of the subduction complex (Xu et a]., 1994; Feng et al., 1996; Xia et al., 1996). It is predominated by metaperidotite (mainly harzburgite and dunit), gabbro, diabase and basalt. The basalt and diabase were formed in ocean ridges (Zhang et al., 199%). The Dachadaban ophiolite belt is composed of metaperidotite, gabbro, diabase and pillow basalt and is characterized by developed vitric andesite (Chen et al., 1995). The diabase shows the characteristics of the NMORB. The pillow lava and intrusive gabbro and diabase also have the characteristics of vitric andesite, which indicates that the ophiolite was formed in a forearc or interarc spreading environment. The Jiugequan (Tadungou) ophiolite belt meets the Laohushan opholite in the east. The latter is composed of serpentinized harzburgite, gabbro, pillow basalt and silicolite. The harzburgite is equivalent to the strongly depleted mantle peridotite (Zhang and Zhou, 2000) and the basalt to the N-MORB. The relict clinopyroxene in the basic rocks has the characters of the VAB and OFB, which suggests that the Laohushan ophiolite was formed in a back-arc spreading ridge (Fen et al., 1995). A SmNd isochronal age of 453k4 Ma was determined from the volcanic rocks. and Middle-Late Ordovician radiolarian fossils were found in the overlying siliceous rocks (Xia 1996; Zhang et al., 1997), which imply that the ophiolite was formed in the Early-Middle Ordovician. The Jiugequan ophiolite contains mantle peridotite, cumulativegabbro, homogeneous gabbro and pillow basalt (Zhang et al., 1997b). The relict clinopyroxene intermediate-basic rocks have the characteristics of volcanic arc basalt (Feng et al., 1995). The formation environment and time of the Jiugequan ophiolite, therefore, should be very similar to those of the Laohushan ophiolite (Feng, 1995; Xia 1996; B a n g et al., 199%). In a word, the North Qilian suture is a large accretionary wedge composed of ophiolitic melange,Vol. 75 No. 4ACTA GEOLOGICA SINICADec. 2001367bluechist and eclogite formed in ocean ridges, ocean islands, trenches, arcs, back-arc basins, and microblocks. The ophiolites were formed in the period from the late Neoproterozoic to early Palaeozoic, particularly in the Late Cambrian-Ordovician (Xiao et al., 1978; Xia et al., 1996; Feng et al., 1996; Zhang and zhou, 2000).(3) The Qaidam northern marginal suture zone The WNW-stretching northern marginal suture zone is about 600 km long and 20-30 km wide. It is interbedded with the south-central Qilian block and Qaidam block and links the Altun and the Qimantag-Wutuo sutures in the north and the south respectively. Along the suture, ultramafite, gabbro, oceanic abyssal tholeiite, semimature and mature arc volcanic rocks and island-arc alkali basalts are developed (Lai et al., 1996; Cui et al., 1999). The early Palaeozoic UHP subduction complex (Yang et al., ; Xu et al., 1999; Zhang, 1999) and the dating of single-grain zircon indicates that the main metamorphic age of the eclogite is 487462 Ma in the north while 495-443 Ma in the south of the Dulan belt of the suture zone, which is in accordance with those from Dachaidan (495 Ma) and Qiemo in Altun (504 Ma) (Xu et al., 1999). Coral and brachiopod fossils in the Tanjianshan Group and the Rb-Sr isochronal age of 464.6 Ma in the metamorphic volcanic rocks (Wu et al., 1987) suggest that the ophiolites were formed in the Early-Middle Ordovician and emplaced in the Late Ordovician.(4) The Qimantag-Wutuo suture zone The Qimantag-Wutuo suture zone is located to the south of Qaidam and north of East Kunlun. It meets the Altun suture zone westerly and the North Qilian-Shangdan suture zone easterly around Yuanyangzhen in the west Qinling region after crossing the Qaidam northern marginal suture. This implies that there should be an ophiolite knot around Yuanyangzhen. The Qimantag subduction complex (Qimantag Group) stretches mainly NNW and joins the Wutuo ophiolite to the south of Golmud. The complex is composed of low-grade metamorphic clastic rocks, volcanic rocks and carbonate rocks. The volcanic rocks consist of pillow basalt, massive basalt and basaltic andesite, intercalated with acid volcanic and volcaniclastic rocks. Near the west end of the zone, the Qimantag Group is 3500 m thick and contains ultramafite and siliceous rocks (Jiang et al.,1992). The Middle-Late Ordovician coral and Cephalopoda in the upper carbonate sedimentary unit suggest that the volcanic rocks in the middle of the group may belong to the Early-Middle Ordovician. The Rb-Sr isochronal age of the biotite granite intruded in the Qimantag Group is 425.92f41 Ma (Xu et al., 1994) and most of the volcanic rocks are calk-alkaline rocks and arc-tholeiite with some similar to the OIB (Cao et al., 1999). The Wutuo ophiolite consists of serpentinized ultramafite, harzburgite, gabbro, diabase, pillow basalt, massive basalt, volcaniclastic rock, siliceous rocks, greeschist and slate. Ordovician and Silurian acritarchs have been found in the slate. The obtained diabase Rb-Sr isochronal age is 426.5k2.9 Ma and the siliceous rocks Rb-Sr isochronal age, 438f46 Ma. Recently, the Neoproterozoic-Early Cambrian acritarch was found in the slate by the authors. All these suggest that the Wutuo ophiolite was formed in the late Neoproterozoic-Late Ordovician. Some basic rocks (diabase and basalt) have characteristics of the E-MORB and some show transitional characteristics between island-arc and NMORB.Massive lavas are mainly calc-alkaline basaltic trachyandesite and the trachyandesite, exhibiting continental marginal arc characteristics (Pan et al., 1996). A geochemical study of the Wutuo ophiolite to the north of Qingshuiquan recently conducted by the authors also indicates the island-arc characteristics of the basic rocks, which have been changed to greeschist. All these lead to the conclusion that the ophiolite and volcanic rocks in the suture may have resulted from a supra-subduction zone (SSZ).(5) East Kunlun southern marginal suture zone The East Kunlun southern marginal suture zone is more than 1200 km long and stretches nearly E-W. It intersects the Kunlun-Altun ophiolite knot in the west and links up with the Mianliie suture zone in the east. Ophiolite mainly outcrops in its east part, the A&#39;nydmaqCn suture belt. The ophiolite consists of serpentinized metaperidotite (mainly harzburgite), pyroxenite, banded cumulate gabbro, homogeneous gabbro, diabase, pillow basalt, massive basalt, radiolarim chert etc., as well as some island arc-type moderate acid volcanic rocks and OIB. Some researchers believe that the suture is the result of the closure of the Permian-Middle Triassic A&#39;ny6maqCn Ocean (Jiang et al., 1992; Xu et al., 1996; Yang et al., 1996;Zhu et al., 1999). Recently, the authors found a well preserved early Palaeozoic ophiolitic slice368Study of the KunlunQilian-Qinling Suture SystemBian et al.in the Buqingshan ophiolitic mtlange. The ophiolitic slice is composed from the bottom to the top of serpentinized harzburgite, gabbro, diabase dykes, basalt, siliceous rocks, silty slate interbedded with black slate, in conjunction with a few thin limestone layers. The black slate found by the authors contains the MiddleLate Ordovician acritarchs (Bian et al., 2001a). The single zircon U-Pb age of the gabbro is 467.2M.9 Ma and the gabbro-diabase Rb-Sr isochronal age is 495.32k80.6 Ma (Bian et al., 1999a). which means that the ophiolite was formed in the Early-Middle Ordovician. Also, granodiorite-tonalite bodies with a single-zircon U-Pb age of 402f24 Ma are seen intruding into the slice (Bian et al., 1999a).In addition, the authors discovered Early and Late Carboniferous radiolarian fossils from the siliceous rocks and pelitic siliceous rocks in other slices in the Buqingshan ophiolitic mtlange. The former includes Callella parvipinosa ? Won and Entactinia variospina ? Won, and the latter Albaillella amplijkata Nazarov et Ormiston, Camptoalatus cf. Benignus Nazarov, and CamptoalarUs sp. In the ophiolitic slices, pillow basalt, massive basalt and metaperidotite are developed. These indicate the existence of the Early Carboniferous-Early Permian ophiolitic slices. Therefore, the East Kunlun southern marginal suture zone is a composite ophiolitic melange zone, which comprises ophiolites of the following three periods: the early Palaeozoic, Early Carboniferous-Early Permian and Late Permian-Middle Triassic (Bian et al., 1999b). The metaperidotite in the Buqingshan ophiolite came from a depleted oceanic mantle. Most of the gabbro, diabase and basalt in the Eerly Palaeozoic ophiolite and the basalts in the Early Carboniferous-Early Permian ophiolite have the characteristics of the N-MORB, while a few have those of the T-MORB. They were all formed in an ocean ridge, which means that mature the early Palaeozoic and Palaeotethyan ocean basins were once developed in the area (Bian et al., 2001b). The Palaeotethyan ophiolitic mklange was superposed on the early Palaeozoic KQQ ocean subduction complex and then covered by the Triassic flysh sediments to form the East Kunlun southern marginal ophiolite&#39; mtlange belt due to tectonic intermixing. The Jinningian ophiolites may also be found in the belt.1.23 The eastem sector o P the KQQ suture systemThe eastern sector of the KQQ suture zone, including theDabie orogen, is almost equivalent to the Qinling orogen. It is composed of the Shangdan and Mianliie suture zones with the central Qinling-Dabie microblock in between. The Shangdan suture zone stretches along the Danfeng, Shangnan, Tongbai, Xinyang, Shangcheng and Jinzhai areas (Jiang et al., 2000) eastwards from the Yuanyangzhen suture knot in western Qinling towards the Tanlu fault, where it is probably offset to eastern Shandong. Ocean-island, island-arc and minor oceanridge ophiolitic slices are developed in the suture zone. These ophiolites, along with large amounts of island-arc volcanic rock blocks, made up an ophiolitic structural complex zone. Isotopic ages of the ophiolites are mostly the early Palaeozoic, from 447 to 357 Ma B.P., and partly the Neoproterozoic, from 1250 to 983 Ma B.P. (Zhang et al., 1996). indicating that the suture zone is also an ophiolitic mtlange, consisting of both the Jinningian and the Caledonian ophiolites. In addition, Middle Ordovician-Early Silurian radiolarias were found in the silicolite in the suture zone (Cui et al., 1995). The Cambrian-Silurian passive continental marginal sedimentary system is developed on the southern side of the suture zone, while banded island-arc granites, whose earliest U-Pb age is 444 Ma, are distributed on the northern side (Zhang et al., 1994). The Mianlue suture zone is an E-W-trending ophiolitic mtlange zone lying at the south edge of the Qinling orogenic belt. It extends eastwards to the south edge of the Dabie Mountains and then is possibly cut by the Tanlu fault to move to eastern Shangdong. More than 100 ultramafic rock blodks, dominated by strongly serpentinized harzburgite and dunite, outcrop along the suture zone, which show geochemical features similar to those of typical ophiolite (Lai et al., 1999). And also, there outcrop gabbro, diabase, N-BORB volcanic rocks, island-arc volcanic rocks (Lai et al., 1999), bimodal volcanic rocks (Lie et al., 1996),radiolarian chert (Yin et al., 1996) etc. The Mainlue suture zone is debatable as regards its development and tectonic background and there have been several arguments in this aspect as follows. The suture zone is the product of the closure of a Carboniferous-Early Triassic ocean basin (Palaeotethys)in the Middle Triassic (Zhang et al., 1996; Meng et al., 1999); it is the product of the closure of a Devonian-Triassic small ocean basin (Lai et al., 1999); it was formed when an early Palaeozoic small basin was partly closed in the late Caledonian-early Hercynian andVOl. 75 NO.4ACTA GEOLOGICA SINICADec. 2001369partly (western Qinling) continued to the late Palaeozoic to complete its closure in the late Hercynian-early Indosinian (Du et al., 1997; Yin et al., 1999); and this suture zone is composed of the Late Palaeozoic and older ophiolites (Xu et al., 2000), and even those of the Jinning Stage. The Mianlue suture zone, therefore, is probably an ophiolite mklange zone comprising ophiolites of three periods: the Jinning, Caledonian and late Hercynian-early Indosinian Stages.2 Evolution of the KQQ Ocean and Formation of the KQQ Suture SystemThe KQQ suture system indicates the existence of the KQQ ocean (Fig. 2). There are abundant records in the KQQ suture system to demonstrate the formation and evolution of the KQQ ocean, which can be basically divided into 3 stages.2.1 Extension-rifting stage of the Rodinia super-continent (in the early-middle Sinian, about 780-600 Ma B.P.) The Neoproterozoic Rodinia super-continent existed in the period of
Ma B.P., and then underwent a rifting process during 780-560 Ma B.P. (Hoffmen, 1991; Li, 1996; Dalziel, 1997; Wang, 1998; Lu, 1998). A suite of Sinian strata, composed of intercalated greenschist and stromatolitic limestone outcrop at the Akazi Pass of the West Kunlun Mountains. The former originated f r o m the continental rift-type basic volcanic rocks and is a typical indicator of continental rifting (Integrated Scientific Expedition to the Qinghai-Tibetan Plateau, Chinese Academy of Sciences, 2000). There are continental rift-type volcanic rocks of the Neoproterozoic Wanbaogou Group in the East Kunlun Mountains. Extensive Neoproterozoic-Cambrian continental rift volcanism was developed in the North Qilian Mountains (Xia et al., 1999) and Neoproterozoic (750-782 Ma) basic dyke swarms were formed in a continental extension-rifting setting in the Wudang microblock and Sui-Zao microblock of the South Qinling Mountains (Zhou et al., 2000). The age and geochemical characteristics of intermediate-basic volcanic rocks in the Yaolinghe Group of the South Qinling Mountains are similar to those of the basic dyke swarms (Zhang et al., 1999). Many continental rifts were formed during the stage (Fig. 3a). 2.2 Formation and evolution of the KQQ ocean Oate Sinian-Ordovician, -600 440 Ma) (Fig. 3b) Some of the rifts formed previously continued their expansion to initiate ocean basins while some faded. As a result, some initial Ocean basins were connected to each other to finally form an archipelagic ocean, consisting of many microblocks, mid-ocean ridges, oceanic islands, island arcs and back-arc basins. Besides ophiolites, many arc-type granite bodies of 5 17-384 Ma developed to the north of the Mazax-Kangxiwar suture tone in the West Kunlun Mountains (Integrated Scientific Expedition to the Qinghai-Tibetan Plateau, Chinese Academy of Sciences, 2000; Jiang et al., 2000) indicate oceanic crust subduction took place in the Late Cambrian. The same arctype granite bodies with ages of 583-402 Ma-60&#39; SOceanic spreading centreFig. 2. Sketch map showing the geographical reconstruction of the Early Ordovician Kunlun-Qilian-Qinling ocean (modified from Scotese et al.. 1990;Zhao et al., 1992;Cheng et al., 1995 and Huang et al.. 1999, except for the KQQ ocean). NA - North A SB - S KZ - K NC - Nofih C TA - Tnrim block: SC - South C AUS - A R I TB - T AR - A I N - I ANT - Antarcticplnte: AFR - A SA - South Amcricnn plate. Microblock I . Central Wtst Kunlun: 2. south-cenual Q 3. Q 4. A 5. M 6. Central QinlingDabie.370Study of the Kunlun-Qilian-QinlingSuture SystemBian et al.b. Late Sinian -Ordovician (600-440 Ma)c. Late Ordovician-Late Silurian (440-400 Ma)&#39;aContinental crust Accretional wedgeaOceanic crustContinental rift GranitoidVolcanic arcFig. 3. N-S schematic tectonic sections through the central sector of the KQQ suture system, showing the formation and evolution of the KQQ Ocean and the KQQ suture system.found to the north of the East Kunlun southern marginal suture zone (Xu et al., 1990; B a n g et a]., 1998; Bian et al., 1999) indicate northward oceanic crust subduction from the terminal Sinian to the early Palaeozoic in the East Kunlun Mountains. Volcanic arc-type granite with an age of 540 Ma was developed in the south-central Qilian microblock on the south side of the North Qilian suture zone (Wen et al., 2000). The subduction-accretion and island-arc magmatism went through the whole Ordovician (Xia et al., 1996; Zhang et al., 1998; Yang, 2000). The Cambrian-Silurian passive epicontinental sedimentary system was developed in the South Qinling Mountains and Cambrian trilobites in the South and North Qinling Mountains belong to two different biogeographical regions, which implies that there existed a fairly large ocean between the North and South Qinling Mountains (Li, 1994). The discovery of the Middle Ordovician-Early Silurian ridiolarians in cherts in the Shangdan suture zone (Cui et a]., 1995) indicates that the Qinling ocean stiil existed in the Early Silurian. A column of island arc-type granite bodies with ages of 444-357 Ma and northward component polarity are distributed along the north side of the Shangdan suture zone (Zhang et al., 1996), whereas island arc-type granite bodies with ages of 380-485 Ma are developedin the central Qinling-Dabie microblock (Jiang et al., 2000). These facts show that the Qinling oceanic crust began to be subducted in the Early Ordovician and that the KQQ oceanic crust was subducted mainly northwards.2 3 The closure of the KQQ ocean and the formation of the KQQ suture system during the Late Ordovician-Late Silurian (-440400 Ma) (Fig. 3c) The biotite from the shist in the northern Kiida area ofthe West Kunlun orogenic belt yields an Ar plateau age of 400.883273 Ma and an Ar-Ar isochronal age of 399.55*4.46 Ma (Jiang et al., 2000). which indicates that the Caledonian orogeny and related metamorphism took place in the area. The Late Ordovician-Early Silurian (445-428 Ma) volcanism characterized geochemically by continental volcanic rocks took place in the North Qilian area because of the closing of the ocean basin (Xia et al., 2000). The North Qilian ocean basin was mostly closed at the end of the Ordovician except for the Ocean remnants in the north part of the area (for example, the Nannigou area of Wuwei County), and the principal part of the North Qilian area came into a collisional orogenic stage in the Early Silurian. The Ocean basin was completely closed in the Late SilurianVol. 75 No. 4ACTA GEOLOGICA SINICADec. 200137 1(Cui et al., 1999). Great changes took place with the sedimentation in the North Qinling ocean basin during the MiddleLate Ordovician. The upper Erlangping Group and the Taowan Group were changed into neritic deposits and the Early Ordovician South China-type biota, consisting of conodonts, cephalopod and brachiopoda, changed into the South China-North China-Qilian type biota in the Middle-Late Ordovician (Li et al., 1994), which indicates that the Qinling ocean was not an obstacle to the intercommunication between the North and South biotas and entered into the closing stage in the MiddleLate Ordovician. By the end of the Late Ordovician, the north Qinling ocean basin had been closed, and the northern and central Qinling was uplifted to become a continent with the Late OrdovicianSilurian deposits being absent. The south Qinling ocean basin was closed and collision and orogeny took place at the end of the Silurian, accompanied by strong metamorphism and magmatism at about 400 Ma B.P. (Zhang et al., 1996). The KQQ suture system was eventually formed, which was overlain unconformable by the Devonian molasse.ophiolitic zones. Therefore, the Jinningian ophiolites from the Rodinia super-continent can exist in ophiolitic zones of the KQQ suture system. The south part of the KQQ suture system was cut and overlapped by the Palaeotethyan suture system. It is not certain that the present Mazar-Kangxiwa-East Kunlun southern marginal-Mianlue suture zone is the original south boundary of the KQQ suture system. Palaeotethys started to open in the KQQ suture system (continent) in the Devonian. Part of the KQQ suture system, including microblocks and suture zones, were involved in the Palaeotethys suture zone, so were the Jinningian ophiolite blocks, thus forming the composite ophiolite zones. The mechanism can also be used to interpret the formation of the above-mentioned Mazar-KangxiwaEast Kunlun southern marginal-Mianliie suture zone. However, there have been arguments on the age and nature of some ophiolites in the KQQ suture system. And, what is more, whether those rocks are really ophiolites is still disputable. The authors hope that their preliminary study, especially the discussion on the relations among the ophiolite zones, could lead to better understanding of the suture system.3 Discussion and New ThoughtsThe KQQ ocean and the Palaeo-Asian ocean were formed by the rifting of the Rodinia super-continent in approximately the same period and can be considered one great ocean. The Tarim block and the North China block located in the ocean were just two super-large islands. The KQQ and Palaeo-Asian oceans were connected then. One evidence for this is that the Middle-Late Ordovician radiolarian assemblages in North Qilian, North Qinling and Kazakhstan have almost identical features (Cui et al., 2000). A suture zone should come into being between the Tarim block and the North China block when the great ocean was closed in the terminal early Palaeozoic. A number of Jinningian ophiolites with ages of 780-1 100 Ma were found in the east sector of the KQQ suture system (Li et al., 1991; Zhang et al., 1994; Dong et al., 1997; Zhou et al., 1998) and have been reported to occur in the central sector of the KQQ suture system (Zhang et al., 1998; Zhu et al., 1999). The Rodinia supercontinent may consist of many blocks and suture zones. The KQQ suture system engulfed and altered the Jinningian ophiolites originating from the suture zones of the Rodinia super-continent to form compositeAcknowledgementsThis study was supported by the National Natural Science Foundation of China (grants
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Earth Science, 24(2) 134-138 (in Chinese with English abstract).About the first author Born in 1945; graduated from the Bian Qiantao Department of Geology, South-Central University of Technology in 1970, and obtained his master’s degree and doctor’s degree at the Graduate School and the Institute of Geology, Chinese Academy of Sciences in 1981 and 1987, respectively. He is currently a professor of the Institute of Geology and Geophysics, Chinese Academy of Sciences, and has long been engaged in the research of tectonics, petrology, mineral deposits and (010) : E-mail: geochemistry. Tel: bianqt@ igcas..
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