1篇
您的检索式：作者名="C.W.Lambert"
|
|
|
题名
|
作者
|
年代
|
出处
|
被引量
|
| 1 | A continental back-arc setting for the Namaqua belt:Evidence from the Kakamas Domain显示文摘A study of the NW Kakamas Domain in South Africa/Namibia provides a new,unified lithostratigraphy and evolutionary history applicable to the whole Namaqua Sector.The Mesoproterozoic history ranges from~1350 Ma to 960 Ma,but isotopic evidence suggests it was built upon pre-existing Paleoproterozoic continental crust that extended west from the Archaean Craton.In eastern Namaqualand,early rift-related magmatism and sedimentation at~1350 Ma occurred in a confined ocean basin.Subsequent tectonic reversal and subduction at~1290–1240 Ma led to establishment of the Areachap,Konkiep and Kaaien Domains.In the Kakamas Domain,widespread deposition of pelitic sediments occurred at~1220 Ma(Narries Group).These contain detrital zircons derived from proximal crust with ages between~2020 Ma and 1800 Ma(western Palaeoproterozoic domains)and 1350–1240 Ma(eastern early Namaqua domains),suggesting pre-sedimentation juxtaposition.The pelites underwent granulite grade metamorphism at~1210 Ma(peak conditions:4.5–6 kbar and 770–850°C),associated with voluminous,predominantly S-type granitoid orthogneisses between~1210 Ma and 1190 Ma(Eendoorn and Ham River Suites)and low-angle ductile(D_(2))deformation which continued until~1110 Ma,interspersed with periods of sedimentation.This enduring P-T regime is inconsistent with the expected crustal over-thickening associated with the generally-accepted collision-accretion Namaqualand model.Rather,we propose the Namaqua Sector is a‘hot orogen’developed in a wide continental back-arc with subduction west of the present-day outcrop.The observed high geotherm resulted from thinned back-arc lithosphere accompanied by an influx of mantle-derived melts.Ductile D_(2)deformation resulted from'bottom-driven'tectonics and viscous drag within the crust by convective flow in the underlying asthenospheric mantle.This extended tectonothermal regime ceased at~1110 Ma when SW-directed thrusting stacked the Namaqua Domains into their current positions,constrained in the Kakamas Domain by late-to post-tectonic I-type granitoids intruded between~1125 Ma and 1100 Ma(Komsberg Suite).The thermal peak then shifted west to the Bushmanland and Aus Domains,where voluminous granites(1080–1025 Ma)were associated with high-T/low-P granulite facies thermal metamorphism and mega-scale open folding(D_(3)).Unroofing of the Namaqua Sector is marked by large-scale,NW-trending,sub-vertical transcurrent dextral shear zones and associated pegmatites and leucogranites at~990 Ma. | P.H.Macey R.J.Thomas A.F.M.Kisters J.F.A.Diener M.Angombe S.Doggart C.A.Groenewald C.W.Lambert J.A.Miller H.Minnaar H.Smith H.F.G.Moen E.Muvangua A.Nguno G.Shifotoka J.Indongo D.Frei C.Spencer P.le Roux R.A.Armstrong C.Tinguely | 2022 | Geoscience Frontiers2022，13，4： | 0 |
您所在的机构暂未开通此部分的功能，请联系管理员