Are volcanic glasses and tektites of the same origin ?

 

Norbert Brügge, Germany

Dipl.-Geol.

Update: 31.10.2017

It is urgently necessary to brake the currently raging impact crater hysteria. With the help of meanwhile established criteria many impact-events became postulated, mostly too quickly and not sufficient examined. All endogenous possibilities were ignored. Still worse, multiple is worked only with satellite pictures. Alone already the origin of so-called tektites or impact glasses is an important discussion. The question is, are volcanic glasses and tektites of the same origin ? Yes, I believe it. It is a disruptive theme, that is conceded.

All of natural glasses found on the earth are from amorphous structure and have a high to very high SiO2 capacity. They are divided in four classes: Tektite, impact glasses and volcanic glasses. However until today is not clarified, whether the practised division of glasses is right to such classes. There is no safety, that the locations of glass finds can be associated e.g. with impact structures, or such are the originally location of glasses.

For the existence of tektites - emerged by an impact event - there is practically no proofs. It has also up to now not been successful, to prove a satisfactory chemical equality between supposed target rocks and glass locations. It is not impossible, that most glasses found on the earth are volcanic of origin. Besides is not finally clarified whether such "typical" criteria for an impact, like the high temperature and high pressure minerals (e.g. Coesite, Stishovite), shatter cone structures, planar deformations in quartz grains or breccias (Suevite) also emerged by very high-dynamic volcanic events. Various localities, which were classified as impact structures, would be then endogenous origin. Striking examples for an uncertain origin are the Vredefort, Sudbury and Popigai structures with clear igneous intrusions.
What kind of enormous dynamics by the explosion of a supervolcano is to be expected, the idea would be, that the magma - chamber under the Yellow Stone Park explodes again. The thrown out masses would be exposed tremendous changes.
During an explosion of the powerful magma chamber a dynamic would emerge presumably, which we do not know up to now. Why should a such powerful explosion not be comparable the dynamics by an impact ?



Popigai structure, Siberia



Sudbury structure, Canada
 



Vredefort structure, RSA
 

The greatest question is however:
 

Can document the "flying glasses" furious volcanic outbreaks ? For that reason, if we believe to know already everything, then we make a mistake. The known example for the unsolved origin of a glass is the Libyan Desert Glass (LDG or LDSG). It has the highest SiO2 capacity of all natural glasses and is surely also no an impact glass.

 

Tektite and impact glasses should be of equal origin. Tektite should be impact glasses, which are found far from the origin location of the impact. In Europe are found the green Moldavite. Tektite of Indochina and Australia are mostly black, some forms are dumbbell-shaped, in part discus-shaped and flattened, also round and spherical in many forms. Tektite have therefore often an aerodynamic form, also a scarred surface with melted structures. The kind of the physical characteristics the tektite resemble of the volcanic Obsidian (the most known volcanic glass).
Tektite should differ from volcanic glasses by a higher SiO2 capacity as well as by an extremely poor water capacity. Also so characteristic inclusion of micro-crystals in volcanic glasses should be missing.To improve the scarce data base of H2O content in tektites and impact glasses, University Wien (Prof. KOEBERL) analyzed 26 tektites from all four strewn fields and 25 impact glass samples for their H2O content. The results show that the tektites have H2O contents ranging from 0.002 to 0.030 wt% (av. 0.014 ± 0.008 wt%). Ivory Coast tektites have the lowest H2O abundances (0.002-0.003 wt%); the Muong Nong-type indochinites and some North American tektites having the highest contents (up to approx. 0.03 wt%). Glasses from the Aouelloul and Zhamanshin craters have low H2O content (0.008 to 0.063 wt%). Libyan Desert Glasses have higher H2O content (approx. 0.11 wt%). Data confirm that all tektites found on land have very low H2O contents (<0,03 wt% H2O), while impact glasses have slightly higher H2O contents. Both glass types are very dry compared to volcanic glasses. Obsidians have water content higher as 0.20 wt%.
It becomes clear, that between all glasses in the capacity of water no separation is to be recognized.

Are this postulated differences between impact glasses/tektites on one hand and volcanic glasses on the other hand a so important characteristic ?
Emerged this differences by differently conditions before and during an eruption. Sure is, that all natural glasses - also tektite and impact glasses - can be associated with volcanic rock types. Extreme exceptions are the LDG, the Urengoite and the Aouelloul glass with very high or extreme high SiO2 content.


 

 

Short Lesson

There are two types of magmatic (igneous) rocks
There is a wide variety of igneous rocks types but only a few basic types of magma, because the asthenosphere and upper mantle have a fairly uniform composition.
Plutonic rocks (intrusive) form when the magma cools slowly beneath the surface, while eruptive volcanic rocks (extrusive) form when magma reaches the surface and cools rapidly.
The mostly igneous rocks are composed of approximately 50 - 80 wt% SiO2, 10 - 20 wt% Al2O3, 1 - 2 wt% MgO, 1 - 5 wt% FeO, 1 - 5 wt% CaO, 1 - 5 wt% K2O, 1 - 2 wt% Na2O.

Igneous rocks with a capacity of < 90 wt% of SiO2 (and that is the predominant part) can be classified in a QAPF - diagram of the presence from light parts in the mixture (felsic) in the rocks. This happens for plutonite and eruptiva in separate triangles after that equal principle.


1. Volcanic glasses

Volcanic glass emerges from quick cooling of gas-poor eruptiva. Volcanic glass can refer to any of several types of vitreous igneous rocks. Most commonly, it refers to Obsidian, a rhyolitic glass with high silica content. Rarer are
Tachylite, a basaltic glass with relatively low silica content.
Palagonite, a basaltic glass with relatively low silica content.
Pele's hair
, threads or fibers of volcanic glass, usually basaltic.
Pele's tears, tear-like drops of volcanic glass, usually basaltic.
Limu o Pele, thin sheets and flakes of brownish-green to near-clear volcanic glass, usually basaltic.


By virtue of the quick cooling can increase no regular crystals. The glass has with it a chaotic, amorphous structure.
The most volcanic glasses have a SiO2 capacity between 50 and 80 wt%, and are arranged in the rhyolith, trachytic, dacitic, andesitic and basaltic families of eruptive rocks.
Volcanic glasses can contain inclusions of radial increased structures, so-called spherolithes. These minerals, mostly feldspars or Cristobalit (a high temperature modification of quartz) increased spherical at a kernel in the surrounding melt, until stopped this process the cooling.

2. Tektite glasses
are similar in chemistry to terrestrial volcanic glass.
From the geochemical point of view the chemical analysis characterizes at all the tektite glasses as rhyolitic or dacitic (
as well as the Obsidian). The melt is oversaturated in SiO2 and molecular Al2O3 and their concentration is but clearly greater than the sum of Na2O + K2O + CaO in comparison to the Obsidian. The tektite glasses are peraluminous.
Also by the alkali-lime index (Na2O + K2O) and CaO in terms of SiO2 the tektite glasses are determined characterized by a rhyolitic composition.
Glasses were formed from a rhyolitic or dacitic volcanic melt. They are characterized as high polymerized network glasses in with respect to their glass structure by the chemical composition, (especially by the SiO2-content), as high polymerized network glasses.






3. "Impact glasses"
Glasses - as the result of an impact classified - have an extensive spectrum of their composition. Accordingly the silica/alkaline index are some glasses nearby the Obsidian or the Tektites. Most glasses can be associated however with volcanic lava or other fluid melts ("Impactite" melt glass).
 

Between Obsidian - the most frequent volcanic glass - and the tektites as well as impact glasses gives however a striking difference of chemistry.
The part of Na2O+K2O is at the volcanic Obsidian approximately doubly so much as at tektitic glasses. That means, that the Obsidian is emerged by rhyolitic-trachytic eruptions, and the tektites (incl. Moldavite) is emerged by rhyolitic-dacitic eruptions. It is not a feature to separate both.
Also is interesting, that the glasses of the El'gygytgyn - classified as impact glasses - have a clear affinity to the Obsidian.
With a great amount of chemical analyses of different glaziers (incl. mikrotektites) the thesis of the volcanic origin of all glasses can be proven (at least of the tektite). The here presented analyses are freely accessible in the internet.

1. Volcanic glass
 
 Hawaii Glass (Hawaii)

 Eruptiva type: Basaltic

 Age: Recently
  

Oxide   (wt%)

Hawaii glass

SiO2

51.80

Al2O3

10.20

TiO2

2.70

FeO

12.0

MgO

8.00

CaO

8.60

Na2O

1.60

K2O

0.40


Volcanic "Pele's tears"



Limu o Pele
   

 Chimgau "Tektite" (Germany)

 Type: Eruptiva

 Age: Pleistocene ?
The so-called tektites of the Chimgau strewn-field are the latest testimonies of a long-living vulcanism, of which numerous structures have been preserved in the southern German region. These include also the Nördlinger Ries and the Steinheimer Becken insistent classified as "impact" craters.

 
       
 

 Atacama "Tektite" (Chile)

 Eruptiva type:

 Age:
In 2014, a new strewn field of splash forms with clearly volcanic origin was found in the Atacama desert.

 
    
 

 Irghizite (Zhamanshin Crater, Kasakhstan)

 Eruptiva type: Dacitic-rhyolitic + Basaltic-andesitic

 Age: 0.9 - 1.1 Ma (Pleistocene)
The Zhamanshin structure is a circle depression ~6 km in diameter. The rim is formed of brecciated rocks. The structure include larger irregularly-shaped fragments and blocks of  glassy melt (Zhamanshinite), and three types of splash-form glasses (Irghizite). These glassy objects typically are up to 30 mm large and are shaped as teardrops, irregularly bent and curved glass rods and fibers. They can be subdivided into acidic types (typically 69–76 wt.% SiO2) and basic types (typically 53–56 wt.% SiO2). That mean, Irgizhite are of dacitic-rhyolitic and basaltic-andesitic origin. The Irghizite glass include bubbles and grains of lechatelierite in some places. The water content of these glasses is with maximum 0.059 wt% atypically for an impactite glass. A volcanic origin of these glasses is much more probable. The Zhamanshin crater would be an endogenous structure with two (?) different eruptions. The related glassy melt bodies (Zhamanshinite) are of the same different origin as the Irghizite.

Oxide (wt%)

Irghizite

Bouska et al. (1981)

Jonasova et al. (2016)

acidic type

acidic type basic type

range (31)

average

range (19)

average

range (5)

average

SiO2

70.00 79.44 74.12 68.04 75.41 72.95 53.48 55.68 54.27

Al2O3

9.45 13.60 10.19 8.49 11.50 9.73 19.93 20.62 20.20

TiO2

0.69 0.99 0.82 0.71 0.83 0.76 0.81 0.87 0.83

FeO

4.24 6.81 5.58 5.50 9.21 6.49 8.19 8.67 8.42

MgO

2.16 3.76 2.82 2.43 4.92 3.18 2.48 2.92 2.73

CaO

1.75 2.85 2.48 2.20 3.93 2.66 6.20 8.35 7.59

Na2O

0.85 1.22 1.09 0.56 1.09 0.97 4.01 4.31 4.17

K2O

1.58 2.14 1.96 1.65 2.04 1.94 1.25 1.44 1.33


        
 

 Glass of Azuara & Rubielos de la Cerida structures (Spain)

 Type: Eruptiva

 Age: Oligocene

Striking breccias rich structures ("Suevite") in Spain are interpreted as impact origin. In truth, they form a chain of probably violent volcanic explosions. The two photos were published by ENSTSON on his homepage and are "glass splashes". The chemical composition should be similar to that of andesites or basaltic andesites.



  

 Mimbral Glass (Mexico)

 Eruptiva type: Andesitic + Trachybasaltic

 Age: ~65 Ma



Glass from the Middle American volcanism
  


Source: Bell & Sharpton (1996)

 Beloc Glass (Haiti)

 Eruptiva type: Andesitic-dacitic

 Age: ~65 Ma


Glass from the Middle American volcanism



Source: Izett et al.(1990) & Stueben et al.(2002)
 

 Obsidian (world wide)  Eruptiva type: Rhyolitic-trachytic  Age: ?
The Obsidian is the classic worldwide occurring volcanic glass. Obsidian is a type of naturally-occurring glass formed as an extrusive igneous rock. It is produced when felsic lava erupted from a volcano cools rapidly through the glass transition temperature and freezes without sufficient time for crystal growth. Obsidian is commonly found within the margins of rhyolitic lava flows known as obsidian flows, where cooling of the lava is rapid.
Obsidian is mineral-like, but not a true mineral because it is not crystalline. It is sometimes classified as a mineraloid. While a rock like basalt is dark because of ferromagnesian enrichment, obsidian consists mainly of SiO2 (silicon dioxide), usually 70% or more. The most Obsidians are arranged in the trachytic and rhyolith families of eruptive rocks. Rhyolithe are the volcanic equivalents of the granites. Because obsidian is metastable at the earth's surface (over time the glass becomes fine-grained mineral crystals), no obsidian has been found that is older than Cretaceous age. Obsidian has a chaotic, amorphous structure. However can be embedded single crystals in more or less great quantities in the glassy mass. Obsidian glasses can contain inclusions of radial increased structures, so-called spherolithes. These minerals, mostly feldspars or Cristobalit (a high temperature modification of quartz) increased spherical at a kernel in the surrounding melt, until stopped this process the cooling. The breakdown of obsidian is accelerated by the presence of water. Obsidian contain approx. 0.2 -0.5 wt% water.
While pure obsidian is usually dark in appearance, the colour varies depending on the presence of impurities. Iron and magnesium typically give the obsidian a dark green to brown to black colour. A very few samples are nearly clear. In some stones, the inclusion of small, white, radially clustered crystals of cristobalite in the black glass produce a blotchy or snowflake pattern (snowflake obsidian). It may contain patterns of gas bubbles remaining from the lava flow, aligned along layers created as the molten rock was flowing before being cooled. These bubbles can produce interesting effects such as a golden (sheen obsidian) or rainbow sheen (rainbow obsidian).
Obsidian can be found in many locations around the world which have experienced rhyolitic eruptions. Obsidian can be found in North America, Mexico, Peru, Iran, Armenia, Turkey, Italy, Greece and Scotland.
The colours in obsidian result from the oxidation state of the chemical elements within the tiny minerals that are finely dispersed in the glass. Black colour results chiefly from magnetite, Fe304. If the obsidian is highly oxidized, then the glass may contain hematite, which provides a reddish hue. Variations in the oxidation state of the iron (Fe) varieties imparts a slight greenish hue. Some obsidian is banded, a consequence of oxidation on a flow surface being folded into the lava as it continues to move.

 

Oxide  (wt%)

Shahryri (Iran)

 Lipari Islands (Italia)

 Yellowstone (USA)

New Mexico (USA)

Nadooshan et al., 2007 Hunt et al., 1998 Hatch et al., 1972 Hölzle-Y., 1992 Rose et al.
range (12) average  range (45) average average (?) average (?) average (?)

SiO2

62.75 79.29 70.90 73.59 75.61 74.26 76.78 75.00 76.40

Al2O3

8.76 12.02 10.73 12.76 13.67 13.16 12.09 12.50 12.70

TiO2

0.09 0.12 0.11 0.03 0.14 0.08 0.08 0.11 0.10

FeO

0.66 1.35 0.96 1.27 1.67 1.50  2.61 1.00 0.58

MgO

0.02 0.23 0.07 0.02 0.07 0.04 0.10 0.03 0.40

CaO

 ? ?  ? 0.66 0.80 0.74 0.57 0.60 0.30

Na2O

3.58 4.10 3.80 2.44 4.27 3.84 3.79 2.90 4.10

K2O

3.48 4.15 4.00 5.00 5.33 5.13 4.93 5.10 4.57

 

Oxide  (wt%)

Anatolia (Turkey)

Bingöl Nenezidag  Erzincan Sakaeli-Orta  Acigöl (E) Acigöl (W) Göllüdag (E) Göllüdag (W)
 ave. (16) ave. (15)  ave. (3)  ave. (6) ave. (15)  ave. (6) ave. (11) ave. (11) ave. (15) ave. (7) ave. (8) ave. (6)

SiO2

74.70 70.90 73.60 72.80 75.70 74.20 74.90 76.10 75.80 75.50 76.30 75.30

Al2O3

11.60 15.70 14.50 14.90 14.10 14.70 14.10 13.80 13.40 13.30 13.00 13.70

TiO2

0.16 0.16 0.13 0.08 0.14 0.08 0.06 0.03 0.05 0.05 0.06 0.11

FeO

2.94 1.34 0.90 1.75 0.75 1.03 0.82 0.67 0.63 0.67 0.65 1.02

MgO

0.08 0.18 0.16 0.08 0.10 0.12 0.07 0.03 0.40 0.47 0.06 0.10

CaO

0.52 0.96 1.18 0.97 0.87 0.96 0.81 0.55 0.67 0.64 0.70 0.88

Na2O

5.80 5.14 4.84 4.36 3.57 4.63 4.46 4.45 4.57 4.94 4.52 4.27

K2O

4.06 4.93 4.40 4.32 4.75 4.34 4.45 4.27 4.58 4.63 4.56 4.14




Dark bands in the brownish matrix







 

 Apache Tears (Arizona, USA)  Eruptiva type: Rhyolitic ?  Age: ?
Apache Tears is Obsidian



 


 Colombianite (Colombia, Peru)  Eruptiva type: Rhyolitic ?  Age: 15 Ma ? (Miocene)
The Columbianite are unusual glasses. They become mainly found in the region of the Orinoco river, Colombia. The glasses were counted up to now among the tektite, because the structure at the surface is similar to tektites. The chemical composition however clearly should correspond the Obsidians.




  
 


     
 

 Darwin Glass (Tasmania, Mt. Darwin)  Eruptiva type: Rhyolitic  Age: ?
The Darwin Glass is found nearby the Mt. Darwin volcanic crater in Tasmania. Chemical analyses suggest the presence of 2 groups of glasses. The ranges in major element composition in group 1 are: SiO2 (80.62 - 93.9%), Al2O3 (3.14 - 10.6%), TiO2 (0.2 - 0.76%), FeO (0.8 - 4.23%), MgO (0.25- 2.31%) and K2O (0.7 - 2.7%). CaO and Na2O are almost completely absent in all analyses. Group 1 glass is predominantly light to dark green, white or sometimes black. The second population has a lower average abundance of SiO2 (81.16%). The average MgO (2.2%) and FeO (3.8%) content in this group is significantly higher than in group 1 glasses and Al2O3 is also slightly enriched. Group 2 glass is predominantly black to dark green and rarely light green in colour. The compositions of the Darwin glasses is similar to the Urengoites and Aouelloul glass. They are volcanic glasses.



  



 

 Libyan Desert Glass (Egypt)

 Type: Hydrovolcanic (like glassy Opal; Hyalite)

 Age: 28 -29 Ma (Oligocene)
The Libyan Desert Glass is classified still always as tektite or impact glass. That is nonsense. The LDG can be arranged in no known class up to now. No natural glass has a SiO2 content with more than 95 wt%. It is in all probability an orthomagmatic-hydrovolcanic glass and is unique on the world up to now. See my report here
 

Oxide (wt%)

Gucsik at al., 2004

Giuli et al., 2003

Guzzafame et al., 2009

bright variety

dark variety

bright

bright

dark streak

yellow

green

range (8)

average

range (6)

average

single

single

single

single

single

single

SiO2

96.40 

98.10

97.20

92.80

97.80

95.97

98.44

98.27

95.85

97.19

96.71

92.52

Al2O3

0.49

1.70

1.12

0.07

2.39

1.30

0.55

1.30

1.48

0.86

1.19

1.88

TiO2

0.06

0.38

0.21

0.15

0.85

0.36

0.08

0.17

0.18

0.07

0.20

0.81

MnO

0.08

0.44

0.24

0.09

0.92

0.31

0.01

0.01

0.02

-

-

0.03

FeO

0.04

0.55

0.22

0.09

1.06

0.36

0.09

0.12

0.98

0.06

0.14

2.09

MgO

0.09

0.51

0.32

0.03

0.58

0.32

0.01

0.01

1.38

0.08

0.11

0.13

CaO

0.04

0.18

0.13

0.09

1.88

0.47

0.01

0.01

0.08

0.08

0.06

0.85

Na2O

0.04

0.43

0.22

0.03

0.40

0.21

0.01

0.03

0.02

0.85

0.99

0.53

K2O

0.05

0.26

0.12

0.14

0.38

0.24

0.01

0.01

0.01

0.27

0.15

0.25







 

 

2. Tektite & Microtektite
 


Tektites
are a group of natural glasses occurring in at least four different strewn fields on earth. The largest strewn field includes Australia, Philippines, Indonesia, Vietnam, Thailand, Cambodia, Laos, Tibet and the southern China. Tektites are generally small, brownish to black, partly transparent, spherically symmetric, and sometimes aerodynamically ablated. Strewn fields are geographically restricted areas on earth where tektites are found, usually in association with microtektites.

Mikrotectites belonging to the Australasian, Ivory Coast, and North American tektite strewn fields have been found in marine sediments adjacent to the respective tektite strewn fields.
Australasian microtektites habe been recovered from approx. 50 cores taken in the Indian Ocean, western equatorial Pacific Ocean, and Philippine, Sulu, Celebes, and South China Seas. The Australasian microtektites are Middle Pleistocene in age.
North American microtektites have been found in Upper Eocene marine sediments on Barbados and in cores recovered from the Gulf of Mexico, Caribbean Sea, and north-western Atlantic Ocean (continental slope off New Jersey). The layers from Barbados indicates an age of ~35 Ma. The major oxide composition and age of the North American microtektites (and tektite fragments) suggest that they too belong to the North American tektite strewn field.
The Ivory Coast microtektites have been found in 11 cores in the eastern equatorial Atlantic Ocean. The layers is also Middle Pleistocene in age (~1.1 Ma). They have a restricted range in major element composition compared with the Australasian and North American microtektites.

 

 Moldavite (Europe)

 Eruptiva type: Rhyolitic

 Age: 14.4 - 15.1 Ma (Miocene)

The Moldavite are rhyolitic glasses. Their affinity to the supposed German impact structures  -- the Nördlinger Ries or the Steinheim basin -- is arbitrary. In the Bohemia and Moravia regions exist numerous Miocene volcanic structures, which come in consideration as source.
 

Oxide   (wt%)

Bouska et al. (1973) etc. Bouska et al. (1973) etc. Bouska et al. (1995) Koeberl et al. (1988)
Moravia Bohemia Cheb Austria
range (21) average range (61) average range (4) average range (7) average

SiO2

74.90 81.40 78.15 75.50 85.10 80.30 78.46 79.89 78.97 78.10 85.10 79.73

Al2O3

9.44 13.80 11.62 7.32 11.40 9.36 8.38 10.13 9.17 8.10 10.60 9.81

TiO2

0.31 1.40 0.85 0.24 0.74 0.49 0.28 0.40 0.33 0.24 0.35 0.30

FeO

1.72 3.50 2.61 1.08 2.93 2.00 1.34 1.86 1.54 1.02 1.78 1.54

MgO

1.13 2.06 2.00 1.34 2.74 2.04 1.86 2.75 2.34 1.10 2.03 1.72

CaO

0.95 3.17 2.06 1.21 3.96 2.58 2.35 4.56 3.60 1.46 3.30 2.41

Na2O

0.40 1.08 0.74 0.20 0.89 0.54 0.31 0.59 0.41 0.19 0.49 0.39

K2O

2.83 3.81 3.32 2.23 3.81 3.02 2.61 3.85 3.24 2.62 3.90 3.49

 

Oxide   (wt%)

Lange (1995)

Southern Bohemia

Radomilice

Western Moravia

Lusatian area

range (43)

average

range (3)

average

range (46)

average

range (15)

average

SiO2

71.90

81.00

78.60

80.00

84.70

82.60

74.91

83.10

79.28

77.2

84.10

79.30

Al2O3

8.96

12.70

10.10

7.27

9.36

8.22

9.27

13.18

11.01

8.94

11.80

10.50

TiO2

0.23

0.50

0.31

0.24

0.29

0.26

0.30

0.72

0.42

0.26

0.42

0.34

FeO

1.28

2.86

1.62

1.00

1.41

1.18

1.40

3.50

2.26

1.32

2.51

1.84

MgO

1.52

3.73

2.33

1.60

2.26

1.91

0.88

2.11

1.39

1.06

2.73

1.75

CaO

2.05

4.48

2.98

1.80

2.82

2.29

0.61

3.11

1.64

0.93

3.85

2.00

Na2O

0.25

0.60

0.42

0.19

0.32

0.24

0.27

1.08

0.57

0.28

0.70

0.47

K2O

2.88

3.77

3.40

2.20

2.97

2.53

2.60

3.81

3.38

3.06

3.75

3.46

 

             





 

 Indochinite (Indochina)

 Eruptiva type: Rhyolitic

 Age: 0.7 - 0.8 Ma (Pleistocene)

Indochinite are Fe-rich rhyolitic glasses. They are found far spreads in a region, in which since long time of the earth history volcanic activities intense presumably already ruled. The large strewn field includes Philippines, Indonesia, Vietnam, Thailand, Cambodia, Laos, Tibet and the southern China. Probable have thrown powerful volcanic explosions the glassy masses until on the Australian craton (Australite).
Within one strewn field, we can distinguish between splash-form tektites (normal tektites) and so called Muong Nong tektites, which differ from normal tektites in respect to a higher volatile content and greater inhomogeneity, besides being of generally larger size.
 

Oxide wt%)

Son & Koeberl (2004)

Chapman & Scheiber (1969)

Koeberl (1992)

Barnes & Pitakpaivan

Lee et al.

Philippines (splash-type)

Vietnam (MN-type)

Philippinite

MN-typ

splash-typ

Phang Daeng (Thailand)

East Asia

range (6)

average

range (11)

average

range (12)

average

average (19)

average (?)

range (5)

average

average (30)

SiO2

71.63

73.21

72.62

74.92

78.14

77.05

67.20

74.90

70.62

78.93

72.70

72.44

80.40

75.42

74.36

Al2O3

11.69

12.04

11.87

10.07

12.20

11.08

8.90

17.70

13.20

10.18

13.37

9.50

13.34

11.72

11.13

TiO2

0.67

0.74

0.71

0.65

0.77

0.71

0.50

1.00

0.76

0.63

0.78

0.62

0.76

0.70

0.78

FeO

3.89

4.30

4.16

3.67

4.21

3.88

3.87

5.87

4.80

3.74

4.58

3.00

4.29

3.72

4.99

MgO

2.08

2.14

2.13

1.52

1.77

1.79

1.87

3.15

2.44

1.43

2.14

1.30

2.00

1.76

2.59

CaO

3.68

3.81

3.77

1.18

1.39

1.27

1.37

9.77

4.08

1.21

1.98

1.10

2.24

1.85

2.14

Na2O

1.09

1.22

1.66

1.04

1.20

1.09

0.91

1.50

1.19

0.92

1.05

1.20

1.62

1.48

1.43

K2O

2.32

2.44

2.39

2.35

2.53

2.46

1.77

2.81

2.34

2.42

2.62

2.20

2.48

2.35

2.39

 

Oxide wt%)

Lee et al. (2003)

Wenchang
(China)

Penglei
(China)

Khon Kaen
(Thailand)

Bao Loc
(Vietnam)

Maoming
(China)

Rizal
(Philippines)

range (5)

average

range (5)

average

range (5)

average

range (5)

average

range (5)

average

range (5)

average

SiO2

72.12

72.69

72.49

71.84

74.49

73.06

72.18

74.07

73.25

72.26

73.61

72.93

77.26

80.61

78.53

75.10

76.95

75.87

Al2O3

12.88

14.32

13.73

12.47

14.61

13.54

13.19

14.47

13.75

12.35

12.81

12.61

5.15

8.46

7.06

5.35

6.99

6.07

TiO2

0.73

0.79

0.75

0.71

0.82

0.77

0.70

0.78

0.74

0.82

0.84

0.83

0.72

0.84

0.78

0.78

0.89

0.82

FeO

5.05

5.34

5.16

4.29

4.72

4.55

4.99

5.34

5.15

4.43

4.56

4.52

4.70

5.52

5.11

5.30

5.63

5.45

MgO

3.15

3.65

3.38

1.47

1.82

1.70

2.57

2.80

2.69

2.57

2.71

2.62

2.10

2.64

2.31

2.71

2.92

2.87

CaO

1.01

1.12

1.10

1.85

2.08

1.97

0.34

0.45

0.43

1.59

2.11

1.76

2.61

3.29

3.01

3.58

5.04

4.58

Na2O

1.33

1.45

1.40

1.40

1.63

1.53

1.33

1.48

1.40

1.24

1.35

1.32

1.18

1.43

1.30

1.57

1.76

1.62

K2O

2.14

2.34

2.30

2.53

2.65

2.61

1.98

2.26

2.15

2.38

2.53

2.45

2.12

2.38

2.27

2.44

2.68

2.54

 



Section through an Indochinite



Thin slice



Vietnam


             
Thailand


China



Philippines

        
China                                                                                            China                                                                                           China



Philippines
 


Philippines

 Tibetanite (Tibet)

 Eruptiva type: Rhyolitic

 Age: 0.7 - 0.8 Ma (Pleistocene)

The specimens from Tibet resembled typical Indochinites in superficial appearance and colour. The results of chemical analysis were essentially identical to Indochinites. By the K/Ar dating found to be 0.76 Ma. also consistent with the Australasian strewn field.
 



 

 Australite (Australia)

 Eruptiva type: Rhyolitic

 Age: 0.7 - 0.8 Ma (Pleistocene)

The Australite like the Indochinite are Fe- rich rhyolitic glasses. Both types belong to the strewn-field "Australasian".
 

Oxide   (wt%)

Australites
(Mason, 1979)

Australites
(Taylor & Sachs, 1964)

Australasian tektites
(Chapman & Scheiber, 1969)

Australasian
 MN-type
(Glass & Koeberl, 1989)

range (60)

average

 range (15)

average

range (51)

average

range (8)

average

average (?)

SiO2

67.30

78.90

 73.06

69.67

77.39

73.53

64.76

82.40

73.58

67.40

73.15

70.28

72.50

Al2O3

9.50

15.90

12.23

 9.84

13.96

11.90

8.20

17.70

12.95

10.90

12.90

11.90

12.94

TiO2

0.59

0.85

0.68

0.60

0.90

0.75

0.43

1.00

 0.72

0.64

0.76

0.70

0.76

FeO

3.55

6.10

4.14

 3.84

5.48

4.66

3.09

8.63

5.86

 5.65

7.82

6.74

4.76

MgO

1.31

3.53

2.04

1.60

2.89

2.24

1.13

7.95

4.54

 3.48

6.38

4.93

2.08

CaO

1.57

5.93

3.38

2.39

4.77

3.58

0.73

9.77

5.25

 2.10

3.47

2.78

2.49

Na2O

0.91

1.74

1.27

 1.05

1.50

1.28

0.62

1.70

1.16

0.62

1.22

0.92

1.42

K2O

2.08

2.78

2.20

 2.07

2.57

2.32

1.34

2.81

2.08

 1.44

2.23

1.84

2.64

 

Oxide   (wt%)

Australites  (Chapman & Scheiber, 1969)

Australites (Taylor &Sachs, 1964)

Australasian Microtektites (Glass et al., 2003)

range (11)

average

 range (23)

average

range (32)

average

range (30)

average

 range (7)

average

SiO2

66.90

79.70

71.13

66.90

 79.70

73.30

69.60

78.70

74.15

60.48

78.05

69.60

66.69

72.01

69.35

Al2O3

 9.30

 16.10

13.72

9.90

 16.10

13.00

9.35

14.00

11.68

10.25

21.46

14.90

12.48

14.94

13.54

TiO2

0.49

0.93

0.79

0.48

0.93

0.70

0.55

0.90

0.72

0.64

1.18

0.82

0.69

0.81

0.75

FeO

3.57

5.43

4.78

3.57

6.06

4.82

3.83

5.38

4.60

2.90

6.32

5.08

5.11

6.77

5.96

MgO

1.31

2.60

2.21

1.31

4.28

2.80

1.49

2.49

1.99

1.67

5.07

3.23

2.90

4.17

3.41

CaO

1.83

5.48

3.45

1.72

5.62

3.67

2.13

5.09

3.61

1.63

6.56

3.52

2.37

4.30

3.06

Na2O

1.00

1.56

1.24

1.00

1.58

1.29

1.05

1.52

1.28

0.28

1.70

0.92

0.98

1.59

1.30

K2O

2.14

2.62

2.39

2.00

2.62

2.31

2.07

2.57

2.32

0.67

2.86

1.83

2.22

2.86

2.57



Flying drops



 

 Ivorite (Ivori Coast)

 Eruptiva type: Dacitic

 Age: 1.1 Ma (Pleistocene)

The rare Ivorite in their chemistry are not absolutely comparable to the Indochinite and Americanite. They are Fe-rich dacitic glasses. The blisters-structure is remarkable, which is comparable with the volcanic Obsidian. As source is supposed the crater Bosumtwi in Ghana. The crater would be then no impact structure, but an explosive volcanic structure.
 

Oxide
(wt%)

King, 1976

Chapman & Scheiber
(1969) etc.

Koeberl et al. (1997)

Microtektites

Glass et al., 2003

Koeberl et al., 1998

average (?)

range (15)

average

average (11)

range (16)

average

average (4)

SiO2

71.05

67.00

69.30

68.15

67.58

63.32

69.30

66.38

67.40

Al2O3

14.60

15.80

17.10

16.45

16.74

15.82

17.62

16.86

17.10

TiO2

0.70

0.52

0.60

0.56

0.56

0.47

0.62

0.55

0.59

FeO

5.51

6.03

6.80

6.42

6.16

6.12

7.49

6.65

6.40

MgO

3.27

2.64

3.93

3.28

3.46

2.91

6.30

4.27

3.70

CaO

1.67

0.71

1.61

1.16

1.38

1.05

2.34

1.73

1.22

Na2O

1.71

1.54

2.44

1.99

1.90

1.60

2.19

1.92

1.63

K2O

1.53

1.70

2.07

1.88

1.95

1.00

2.03

1.60

1.86



 



 

 Zapotektite (Central America)

 Eruptiva type: Andesitic

 Age: 0.8 Ma (Pleistocene)

In the 1990s, three tektites found among glassy archaeological objects at Tikal, Guatemala were studied by Hildebrand et al. Subsequently, Izett and Meeker studied two similar western Belize tektites, one found by J. Cornec near San Ignacio and one found by A. Ford in an archaeological site a few km away. Both tektites have ages like those in and have andesitic compositions. Since 1990, J. Cornec and others have recovered hundreds of tektites, mostly in the 1-3 cm size range, from an area in western Belize.


          

Oxide   (wt%)

 Harris (2011)

Cornec et al. (2016)

SiO2

62.49

61.66

Al2O3

17.58

16.91

TiO2

0.98

0.91

FeO

6.45

7.76

MgO

0.17

1.84

CaO

4.47

4.79

Na2O

3.37

3.75

K2O

1.74

1.91

 

 Americanite (USA)  Eruptiva type: Rhyolitic  Age: 34.5 - 35.5 Ma (Eocene)
Tektites belonging to the North American strewn field are found in Texas (Bediasites), and found in Georgia (Georgianites). One tektite found in Massachusetts (Martha's Vineyard). They are found in Eocene sediments. Microglasses are found in marine sediments nearby the coast and in the Caribbian Sea. They all would be with it clearly the oldest glasses. There is a great amount of chemical analyses. The chemistry of both - the Caribbean glasses as well as the Bediasite and Georgianite - is identical. The Americanite like the younger Australasian are rhyolitic glasses. The Americanites also include the so-called Saffordites (Arizona) and Healdsburgites (California).
 

Oxide
(wt%)

Georgianites

Bediasites

Martha's Vineyard

Cuba
Albin et al. (2000)

Cuttitta et al. (1967)

Wittke & Barnes Chao (1963)

average (24)

range (9)

average

range (25)

average (35)

range (21)

average (21) single single

SiO2

81.80

79.80

83.60

81.50

71.89

81.31

76.36

71.90

80.20

76.37

80.50 74.80

Al2O3

11.20

9.50

11.7

10.71

10.96

17.56

13.77

11.20

17.60

13.78

11.20 15.00

TiO2

0.51

0.42

0.60

0.49

0.53

1.05

0.77

0.59

1.05

0.76

0.53 0.80

FeO

2.64

1.83

3.14

2.50

2.29

5.95

4.01

2.29

5.75

3.98

2.69 4.40

MgO

0.61

0.37

0.69

0.55

0.37

0.95

0.69

0.37

0.95

0.63

0.69 0.70

CaO

0.45

0.40

0.69

0.51

0.41

0.96

0.56

0.49

0.96

0.65

0.69 1.20

Na2O

2.44

1.00

1.53

1.19

1.20

1.84

1.51

1.20

1.84

1.54

1.00 1.10

K2O

0.94

2.22

2.51

2.39

1.60

2.43

2.04

1.60

2.43

2.08

2.37 2.00

 

Oxide
(wt%)

Microtektites, NA Mikrotektites

Tektite Barbados

Microtektites Barbados
Wittke & Barnes Glass et al.

Koeberl & Glass (1987)

Glass et al. (2003)

Koeberl & Glass (1987)

range (55) average (25) single single single aver. (9) aver. (27) single single single range (18)

SiO2

63.52 84.16 73.4

79.50

79.10

77.40

80.40 76.10

77.40

79.50

82.00

76.90 85.60

Al2O3

8.15 17.75 14.10

12.50

12.10

12.90

11.30 12.4

13.50

12.10

10.30

7.97 14.80

TiO2

0.30 1.08 0.73

0.62

0.43

0.69

0.56 0.55

0.71

0.59

0.41

0.40 0.71

FeO

2.06 6.24 4.37

2.35

2.42

3.02

2.75  4.27

3.98

3.45

2.48

1.37 3.98

MgO

0.00 3.26 1.73

0.74

0.92

0.80

0.46 1.08

0.64

0.58

0.48

0.13 1.13

CaO

0.27 2.97 1.64

0.19

0.74

0.75

0.68 1.12

0.59

0.57

0.65

0.52 0.87

Na2O

0.17 3.04 1.06

1.17

1.24

1.23

1.27  1.18

1.26

1.29

1.23

1.15 1.52

K2O

1.91 4.03 2.92

2.49

2.71

2.73

2.25 2.69

1.94

1.93

2.42

1.73 2.54

 

Oxide
(wt%)

Tektite, DSDP 612

Mikrotektite, DSDP 612

Microtektites DSDP 612

 Microtektites DSDP 904

Microtektites RC9-58

Koeberl & Glass (1987)

Glass et al. (2003)

 Glass et al. (2003)

Glass et al. (2003)
single single single single single single range (8) average (23) average (28) range (11) average

SiO2

72.30

74.20

77.60

71.36

73.37

75.28

71.90 77.80 72.30

74.60

62.74 77.05 72.17

Al2O3

15.10

14.00

13.10

15.44

14.47

13.19

13.00 15.10 15.40

13.90

12.17 17.72 13.44

TiO2

0.85

0.77

0.56

0.87

1.01

0.71

0.55 0.85 0.78

0.71

0.58 1.00 0.75

FeO

4.80

4.50

2.80

5.18

5.00

4.19

2.70 5.00 4.03

4.03

3.09 6.66 4.75

MgO

1.20

1.10

0.70

1.15

1.14

1.02

0.70 1.40 2.18

1.22

0.97 4.32 2.02

CaO

0.85

0.90

1.00

1.13

0.74

0.99

0.80 1.00 1.42

1.00

0.88 3.95 1.91

Na2O

0.30

0.20

0.50

1.47

0.57

0.78

0.20 0.60 1.04

0.65

0.62 1.42 0.99

K2O

3.80

3.60

3.10

2.95

3.61

3.02

3.00 3.80 3.27

3.21

2.64 3.70 3.04

 

Oxide
(wt%)

Microtektites DSDP 94 Microtektites DSDP 94, 149 Glass Shards DSDP 149 Microtektites DSDP 149 Microtektites DSDP 149
Glass et al. (2003) Glass & Swart (1979) Donelly & Chao Glass et al. (2003) Donelly & Chao
range (11) average average (29) range (5) average single single single range (7) average

SiO2

68.66 81.51 75.68  69.20 74.80 77.30 76.18 70.72 71.38 72.22 60.60 71.50 67.90

Al2O3

10.82 17.62 13.26 16.90 12.60 13.90 13.24 16.30 14.57 15.63 14.10 18.30 15.80

TiO2

0.46 0.92 0.68 0.59 0.31 0.39 0.35 0.84 0.73 0.85 0.64 0.98 0.81

FeO

2.28 5.98 3.77 5.12 2.60 3.10 2.84 4.68 4.29 4.90 4.00 6.60 5.11

MgO

0.80 2.62 1.41 2.25 0.26 0.48 0.37 1.68 1.95 1.48 1.27 10.20 3.18

CaO

0.43 2.66 1.40 1.65 1.88 2.30 2.03 1.56 1.55 1.15 1.21 3.60 2.01

Na2O

0.77 1.46 1.12 1.34 1.34 1.82 1.54 1.01 1.24 0.89 0.88 1.89 1.16

K2O

1.64 3.16 2.91 2.73 0.94 1.42 1.18 3.20 4.30 2.86 1.11 3.40 2.80


               

Bediasite

Georgianite


           

        Bediasite                                                                                                                                                     Georgianite


                     

 

3. Glassy lava

 Dakhla Glass (Egypt)

 Eruptiva type: Andesitic

 Age: 28 -29 Ma (Oligocene)

The Dakhla glass is found in the western desert, nearby the oasis Dakhla. The Dakhla Glass (DG) is a glassy andesitic lava (see my report here). The Dakhla  Glass (DG) has emerged at the same time like the Libyan Desert Glass. Both differ however by the chemistry significantly. The DG has nothing to do with the LDG. The Dakhla Glass after transport and destruction was deposited in a new position. Now it is found as clumps in younger sediments.

 

 



 

 Edeowie Glass (Australia)

 Type: Volcanic

 Age: 0.67 Ma (Pleistocene)

In the South Australian Outback between the Flinders Ranges and the salt pan of Lake Torrens, roughly 400 km north of Adelaide, irregular masses and flat slabs of visicular, slaglike and glassy silicate melt have been found, locally quite abundant. These slabs of melt are associated with outcrops of baked sediments exhumed by water erosion and deflation. Features in quartz grains and Lechatelierite are present in the Edeowie Glass

      
 

 Turkish Glass (Turkey)

 Type: Volcanic

 Age: Pleistocene ?

Two Turkish mining engineers, Fatih Yüksel and Mehmet Topay, recently found specimens of volcanic glassy lava in the Turkish territory. They sent me photos and a spectral report of it. The samples were found in the region of the western Taurus mountains (near Burdur). This glassy lava is very similar to the Australian Edeowie glass.

Donald Kasper, Lancaster, California, wrote me in this sense: "The images show a pahoehoe lava. This type is highly fluid lava that forms glassy surfaces by quick cooling. In the shown spectral report the main peak must be quartz. The peak to the left would be tridymite. Lava would have magnetite peaks, but they are not evident in infrared spectroscopy in volcanic glasses I have studied so far."



 



 

 

 "Flädle" from Nördlinger Ries (Germany)

 Eruptiva type: Dacitic-andesitic

 Age: 15 Ma (Miocene)

The Nördlinger Ries and the Steinheim basin are interpreted meanwhile as classical impact structures. The famous "Suevite" should be an impact breccias and no volcanic breakout masses. The glass-bombs and glass-inclusions in the suevite ("Flädle") are interpreted as impact-melts. Also the occurrence of Shatter Cones prove apparently an impact event. The analyses of glass-melts against it point to it, that a dacitic-trachytic eruptiva quickly cooled down. The volcanic origin of the Nördlinger Ries and the Steinheim basin is by no means impossible. The Nördlinger Ries is located within the both large volcano regions in Germany, to which belong Eifel, Westerwald, Vogelsberg, Rhön on one hand and on the other hand in south the Kaiserstuhl, Steinsberg, Hegau and Urach.
Also here the question again: Are shock-metamorphe criterias exclusively reserved for impact events ? Was the Nördlinger Ries against all opinions perhaps an explosive volcano ?



Suevite with "Flädle"

Oxide (wt%)

Engelhardt, 1966

average (9)

average (17)

average (6)

SiO2

63.54

64.04

62.07

Al2O3

15.10

15.28

14.72

TiO2

0.81

0.78

0.85

FeO

3.75

2.39

3.37

MgO

2.71

1.71

2.63

CaO

3.45

3.98

3.62

Na2O

2.86

3.59

3.53

K2O

3.71

3.50

3.29



Glass -"Flädle"



Glass bomb


Source: www.carionmineraux.com
 


Section of glass bomb
 

 Glass of Rio Cuarto & Centinela del Mar regions (Argentinia)

 Type: Differently eruptiva

 Age: between   0.5/  3.3/ 10 Ma

Three new strewn fields of "impact" glasses was located in Argentinia along the coastal sequences near Centinela del Mar and from near Rio Cuarto. These highly vesicular glasses contain evidence for an impact origin including temperatures sufficient to melt most mineral constituents (1700°C) and to leave unique quench products such as cristobolite. High-resolution 40Ar/39Ar dating methods yielded different ages of 0.5 Ma (Rio Cuarto) as well as 0.6 + 3.3 +10.0 Ma (Centinela del Mar).
All glasses are from similar chemical composition. The glass shards from the Rio Cuarto region (below) are an originally Fe-rich trachy-basaltic to trachy-andesitic eruptiva.

 

Oxide (wt%)

Glass scrap (1)

Sherules

clear part

brown p.

brown p.

brown p.

dark part

average (5)

SiO2

58.40

58.30

50.90

55.30

48.60

69.00

Al2O3

25.10

15.80

18.20

15.30

14.50

16.30

TiO2

0.00

2.00

1.40

2.70

3.50

0.64

FeO

1.40

10.30

13.70

14.00

20.10

3.80

MgO

0.34

1.70

2.30

2.80

2.30

1.40

CaO

6.50

4.15

8.00

4.80

5.00

3.40

Na2O

5.40

4.30

3.10

3.70

3.00

3.50

K2O

3.20

2.80

1.80

2.40

1.80

2.60



Glass scrap from the Rio Cuarto region


4. "Impact" glassy melt
 

 Fluidal glass of Sudbury structure (Canada)

 Eruptiva type: Andesitic

 Age: 1850 Ma (Proterozoicum)

 

 

The Vredefort and Sudbury structures are probably the remains of the oldest supervolcanos on the earth. In the Sudbury structure (Slave Kraton) the oldest glassy melts are found in breccias. The SiO2 / Na2O + K2O ratio is of andesitic to dacitic composition. This correlates not with the noritic magma but with glasses of  intrusions in the "Onaping" formation.

 

 "Impact" melt glass of Chicxulub crater (Yucatan, Mexico)

 Eruptiva type: Andesitic

 Age: ~65 Ma

Why the Chicxulub-impact was an explosive supervolcano


                     

Glassy melt from Yaxcopoil-1 borehole (-864/834 m)

Pure andesitic melt from borehole Yucatan-6 (-1400 m)

 Fluidal glass of El'gygytgyn crater (Chukotka, Siberia)

 Eruptiva type: Dacitic-trachytic

 Age: 3.6 Ma (Pliocene)

Chemical analyses of the glasses points to a dacitic-trachytic eruptiva. The chemistry has a high affinity to the Obsidian. The crater El'gygytgyn has a diameter of 18 km. The crater was formed in volcanic rock strata, which include tuffs and tuff-breccias as well as eruptive rocks of "basalts". The crater should be an impact - structure, because shock methamorphe features were shown. An explosive volcanic origin of the El'gygytgyn is much more probable however.
Also here the question again: Are shock-metamorphe criterias exclusively reserved for impact events ? No !
 

Oxide   (wt%)

Gurov & Koeberl (2003) Gurov & Koeberl (2003)  Gurov et al. (2005)
Melt glass Glass bombs Melt glass Glass bombs
range (9) average single single single single single single average (25)

SiO2

68.60 70.44 69.63 70.50 71.91 71.62 70.22 73.07 69.37 69.70

Al2O3

14.41 15.84 15.22 15.41 14.23 15.21 15.79 14.30 14.69 15.12

TiO2

0.29 0.47 0.38 0.38 0.36 0.42 0.37 0.25 0.39 0.36

FeO

2.30 3.08 2.53 3.23 2.94 3.00 2.86 1.92 3.31 2.72

MgO

0.69 1.77 1.38 1.17 1.03 1.20 0.90 0.47 0.97 1.20

CaO

2.61 3.14 2.86 2.68 2.32 2.68 2.73 1.46 2.63 2.74

Na2O

2.66 3.16 2.87 2.72 2.74 2.17 3.13 2.62 3.24 2.90

K2O

3.30 4.37 3.72 4.00 3.91 3.94 4.36 4.12 4.10 3.76



Glass bomb


Fluidal inhomogeneous glass



Source: impactites.net
 



 

 Fluidal glass of Zhamanshin crater (Kasakhstan)

 Eruptiva type: Dacitic-rhyolitic + Basaltic-andesitic

 Age: 0.9 - 1.1 Ma (Pleistocene)

The Zhamanshin structure is a circle depression ~6 km in diameter. The rim is formed of brecciated rocks. The structure include larger irregularly-shaped fragments and blocks of  glassy melt (Zhamanshinite), and three types of splash-form glasses (Irghizite). These glassy objects typically are up to 30 mm large and are shaped as teardrops, irregularly bent and curved glass rods and fibers. They can be subdivided into acidic types (typically 69–76 wt.% SiO2) and basic types (typically 53–56 wt.% SiO2). That mean, Irgizhite are of dacitic-rhyolitic and basaltic-andesitic origin. The Irghizite glass include bubbles and grains of lechatelierite in some places. The water content of these glasses is with maximum 0.059 wt% atypically for an impactite glass. A volcanic origin of these glasses is much more probable. The Zhamanshin crater would be an endogenous structure with two (?) different eruptions. The related glassy melt bodies (Zhamanshinite) are of the same different origin as the Irghizite.

 

Oxide (wt%)

Zhamanshinite

Zhamanshinite (Si-rich)

Zhamanshinite (Si-poor)

Bouska et al. (1981)

Bouska et al. (1981)

Bouska et al. (1981)

range (12)

range (5)

average

single

range (16)

average

single

single

SiO2

62.90

88.10

75.50

71.46

77.80

73.89

 72.01

52.42

56.73

54.34

55.34

53.79

Al2O3

14.80

21.20

18.00

10.99

15.55

13.25

15.55

19.61

22.16

20.59

22.16

20.07

TiO2

0.23

1.10

0.66

0.58

0.81

0.70

0.78

0.69

1.09

0.87

0.69

0.79

FeO

1.98

8.05

5.02

4.05

5.50

4.84

5.50

4.68

8.15

7.45

4.68

7.68

MgO

0.34

1.16

0.75

0.71

1.11

0.87

1.11

1.82

3.23

2.73

3.23

2.74

CaO

0.55

2.16

1.36

0.55

1.81

0.89

0.55

6.68

9.07

8.45

6.68

8.91

Na2O

0.57

1.84

1.20

0.88

1.85

1.43

1.10

3.24

4.55

3.94

4.55

3.48

K2O

0.10

3.07

1.58

2.70

2.99

2.89

2.89

1.22

1.85

1.40

1.84

1.42

 


      
      
 

 Glassy Tagamite  (Popigai structure, Siberia)

 Eruptiva type: Andesitic-dacitic

 Age:  35.7 Ma (Late Eocene)