Post Siberian P-T superplume dyke belt in northern margin of Siberian platform

Victor RyabovInstitute of Geology and Mineralogy, SB RAS, Novosibirsk, Russian

Federation

The Low Triassic dyke swarm belt is strengthening at about 500 km along the northern margin of Siberian platform D ike area spread is limited to the north rift structure of the Yenisei-Khatanga trough, and from the south - Kystyktah-Ayan-Ambardah uprise.   From west to east dyke belt is routed through Norilsk, Kamensky and Maimecha-Kotuiskaya province. In this regard, the composition of dykes varies from basic rocks through basic and alkaline-alkaline to alkaline-ultramafic. Power dykes varies from 0,5-10m up to 90 m, length - from 5-15 m to 140 km. The orientation of the bulk of dykes coincides with the direction of the major structural and tectonic elements of the region. dykes are often confined to the fault plane and along the strike of the dykes of different composition are replaced by dykes. Within dyke hundreds of small intrusions in the basalts are unevenly distributed. They form a compact package and swarms of dykes, stocks and subplastovye veins. An example is a portion of the package dykes p. Huor-Uyallah where at a distance of 2 km there are 20 subparallel dykes of different chemical composition. Power ranges from 1.5-2m dykes up to 15m, the distance between the dykes from 4-5 to 150 m. Lack of convincing some cases the intersection of dykes others on this and other sites gives reason to assume the formation of the dykes within a tectonic and magmatic cycle. dykes cross cut the entire incision plateau basalts volcanic strata. They are not for pokrovoobrazuyuschimi effusions and are at the final stage of the platform trap magmatism. Ar / Ar age of the youngest dykes in the province Kamenska 238-247 million years old, the age of minette dyke (LAMPROITES) in the province of Norilsk 235 million years.dykes are presented dolerite trachydolerites, syenite, Minetti, bostonitami, different in composition lamprophyres (camptonite, spessartite, Vosges), avgitite, melanephelinite, alnёite, limburgite alkaline picrites, meimechites. The content of major oxides in rocks of the dykes vary widely: SiO2 35,7-62,6 wt.%; TiO2 0,4-7,5 wt.%; Al2O3 4,4-17,5 wt.%; Fe2O3 4,6-20,6 wt.%; MnO 0,08-0,44 wt.%; MgO 0,8-31,5 wt.%; CaO 0,7-15,4 wt.%; Na2O 0,01-6,5 wt.%; K2O 0,8-5,3 wt.%; P2O5 0,1-1,2 wt.%. Most highly alkaline dykes of basic rocks Bolsheavamskaya volcanic basin, which is dedicated to Kamenskaja province. Here, among the dykes stand undifferentiated and layered dykes, glassy and crystalline, single and multi-phase, with symmetric and asymmetric internal structure, with family and / or contrasting composition of the rocks of the individual phases. Multiphase dykes in the area of the river. Namakan have a structure "in the dyke dyke" and symmetrical internal structure. Vitreous dykes are usually composed of olivine clinopyroxenites, sometimes they are in the center of picritic porphyry. The number of phases in the implementation of dykes reaches five. Symmetric with respect to the axis of the body structure creates similar in structure and composition of the left and right semi- dyke. Each phase of the implementation structure "in the dyke dyke" consists of the quench zone endocontact globules silicate glass and carbonate and the inner zone enriched Ozell K-feldspar, potassium feldspar with Kaersutite and / or mica. In crystalline dykes The contact zones are composed variolitic clinopyroxenites, central - Picritic porphyries. Clinopyroxene is present in the composition of various rocks. Endocontact zone composed of many dykes clinopyroxenites that have arisen as a result of heteromorphic crystallization at a supercooled melt. A feature of the composition of clinopyroxene are elevated content CaTi- and CaAl-tschermak components that support the alleged heteromorphic melt crystallization.

12345678910

Fig.1A. The location of the dyke zone Kamenskaya province alkali-basic rocks in the Northwest of the Siberian platform

Fig.1B The location of the dyke zone A plot of the dyke zone north of the Siberian platform in the Kamenskaya province. Bold lines- alkali-basic and ultrabasic dykes, bold dashed-dotted line - foults, dot dash dot- boundary of Siberian platform.

Kamenskaya province alkali-basic rocks in the Northwest of the Siberian platform. Dotted line border trap basalts fields of the Siberian platform and Taimyr orogen. Black rectangle - Kamenskaya alkali-basic province

Fig. 2. Schematic map of distribution of high-magnesium lavas at the Northwest of the Siberian Platform (Ryabov VV, Shevko AYa, Gora MP. Trap Magmatism and Ore Formations in the Siberian Noril'sk Region / Modern Approaches in Solid Earth Sciences 3. Vol.1. Trap Petrology. Springer. 2014. 390 Р. 1 – dykes of mafic (a) and alkali-mafic – ultramafic (b) rocks; 2 - paleovolcanoes; 3 – areas of maximum density of picritic basalts of the Gudchikhinsky Suite. Various hatching shows distributive areas and ages of high-magnesium lavas. Inset: the main abyssal faults are shown: 1 – Noril’sk-Kharaelakhsky; 2 - Letninsk-Imangdinsky; 3 - Pyasinsky; 4 - Kystyktakhsky; 5 - Changaginsky; 6 - Romanikhinsky; 7 - Bajkal-Taimyrsky; 8 - Enisej-Giulinsky; 9 - Rassokhinsky; 10 - Boganidsky; 11 - Mikchandin-Boruryakhsky; 12 - Kourejksky.

Fig. 3. Mica picrite Dyke N-59/72. Namakan River dyke landfill.

Fig. 4. Dyke alkali augite picrites- N-27/34. Namakan River dyke landfill

Fig. 6. Sketches of the internal structure of glassy and crystalline symmetrical dykes.Variolitic structure, porphyritic. Phenocrysts: augite (black plate and branched dendrites), plagioclase (unfilled rectangles), olivine (hexagons: black - fresh crystals unfilled - modified), small circles - the amygdala.

Fig. 5. Dyke dolerite NU-9/11. Polygon river dyke Uohir.

Fig. 7. Photomicrographs of some types of dyke rocks.

Fig. 12. Variation diagram oxides (content in wt.%) In the context of the multiphase dykes H-27/34. Broken lines shows the composition of rocks IV-V phase in the other section of the dyke. Roman numerals - the implementation phase of the melt.   

Fig. 8. Diagram (Na2O + K2O) - SiO2 dykes north of the Siberian platform (uploaded circles). Gray box - the composition of rocks layered intrusion Dyumtali in Taimyr.

Fig. 9. Composition diagrams (wt%) of high-magnesium magmatic rocks of the Northwest of the Siberian Platform (Ryabov VV, Shevko A.Ya, Gora M.P. Trap Magmatism and Ore Formations in the Siberian Noril'sk Region / Modern Approaches in Solid Earth Sciences 3. Vol.1. Trap Petrology. Springer. 2014. 390 R.On the diagrams, the dots for compositions of small intrusions (K) of the Kamensky and Ust'-Delkansky Complexes units are plotted. Suites: ar - Arydzhangsky; an - Ayansky; dl - Delkansky; gd - Gudchikhinsky; hn - Khonnamakitsky; mm -Maimechinsky; mr - Morongovsky; tk - Tuklonsky.

Fig. 10. Dykes alkaline core (red) and fundamental (green) rocks in basalts Mokulaevskoy Formation (purple box). Polygon river dyke Huor-Uyalllah. At a distance of 2 km from the 21 dyke.

0

4

8

0,0

0,1

0,2

3

5

7

9

11

0,04

0,08

0,12

0,16

0,2

0,4

0,6

0,7

1,1

1,5

1,9

0,5

0,9

1,3

1,7

8

12

16

10

15

20

25

0,1

0,3

0,5

12

14

16

4

6

8

2

3

4

34

36

38

40

SiO2 Na2O

TiO2 K2O

Al2O3 P2O5

Fe2O3 Ba

MnO П.п.п.

MgO Sобщ.

CaO CO2

| I | II | III | IV | V | IV | III | II | I | | I | II | III | IV | V | IV | III | II | I |

Рис.4. Вариационная диаграмма оксидов (содержание в мас.%) в породах по разрезу дайки Н-27/34. Штрих-пунктиром показан второй вариант строения IV-V фаз в другом сечении дайки. Цифрами обозначены фазы внедрения расплава.

Fig.13. Depending on the content of the chart some of the mineral-oxide (wt.%) In clinopyroxene glassy (box I) and crystalline (field II) dykes landfill Namakan. 1-4 - center (1), the edge (2) phenocrysts, microlite (3), dendrite (4) of the dyke H-27/34; 5-7 –Center (5), the edge (6) phenocrysts, microlite (7) of the dyke N-125; 8-10 - center (8), the edge (9) phenocrysts, microlite (10) from the dykes H-121, H-126, H-127, H-132, H-13.

Fig. 11. The chemical composition of subparallel dykes River Huor-Uyalllah. Oxide content in wt.%. Bathed in circles - the central part of the dyke, unfilled - edge parts of the same body.

dykes River Area Huor-Uyallah

Dykes in Namakan River Area. The composition of clinopyroxene rock dyke polygons Namakan and Huor-Uyallah the diagram Hess and features of the distribution of Ca-chermakitogo components in them I - glassy rock dykes Namakana,II - crystalline rock dykes Namakana,III - dykes Huor-Uyallah

0 ,711

0 ,70 7

26 025 024 023 00 ,7 0 3

0 ,71 5

1 006 0 8 04 02 00

В ы де л е н н ы й A r, %3 7

2 40

1 60

Воз

раст

, млн

лет

8 0

Т р а х и д о л е р и т Л П

1 006 0 8 04 02 00В ы де л е н н ы й A r, %3 7

2 40

1 60

Воз

раст

, млн

лет

В о г ез и т

8 0

1 006 0 8 04 02 00В ы де л е н н ы й A r, %3 7

2 40

1 60

Воз

раст

, млн

лет

8 0

Б о с то н и т

1 006 0 8 04 02 00В ы де л е н н ы й A r, %3 7

2 40

1 60

Воз

раст

, млн

лет

8 0

Т р а х и д о л е р и т Л Б -1

( S r/ S r)87 860

1 006 0 8 04 02 00В ы де л е н н ы й A r, %3 7

2 40

1 60

Воз

раст

, млн

лет

8 0

И К К - 6 3

0 ,711

0 ,70 7

26 025 024 023 00 ,7 0 3

0 ,71 5

1 006 0 8 04 02 00

В ы де л е н н ы й A r, %3 7

2 40

1 60

Воз

раст

, млн

лет

8 0

Т р а х и д о л е р и т Л П

1 006 0 8 04 02 00В ы де л е н н ы й A r, %3 7

2 40

1 60

Воз

раст

, млн

лет

В о г ез и т

8 0

1 006 0 8 04 02 00В ы де л е н н ы й A r, %3 7

2 40

1 60

Воз

раст

, млн

лет

8 0

Б о с то н и т

1 006 0 8 04 02 00В ы де л е н н ы й A r, %3 7

2 40

1 60

Воз

раст

, млн

лет

8 0

Т р а х и д о л е р и т Л Б -1

В о зр аст, м л н л ет

( S r/ S r)87 860

1 006 0 8 04 02 00В ы де л е н н ы й A r, %3 7

2 40

1 60

Воз

раст

, млн

лет

8 0

И К К - 6 3

М о н ц о н и т 5 0 2

М и н е т т а З П

0 ,7 0 3 0 ,7 0 5 0 ,7 0 7 0 ,7 0 9 0 ,7 0 113 5

4 5

5 5

6 5

( S r / S r )8 7 8 6

I

0 ,7 0 3 0 ,7 0 5 0 ,70 7 0 ,7 0 9 0 ,70 11

( S r / S r )8 7 8 6

I

3 0 0 0

2 0 0 0

1 0 0 0Sr,

pp

m

3 5 4 5 5 5 6 5

30 00

20 00

10 00

Sr, p

pm

3 5 4 5 5 5 6 5

0 ,80 ,6

1 ,0

0 ,2(FeO

+F

eO

)2

3

(FeO

+F

eO

+M

gO)

23

230 240 250 2600

5

10

15

20

25

Ar-Ar ages of the dykes

Melts in equilibrium with the phenocxrystsOf the dykes

Ar-Ar age spectra

DykesSills and flows Early

sills