Cherts and Siliceous Sediments

Question 1

The general name for the siliceous sedimentary rocks.

Answer 1

Chert

Question 2

What are the dominant minerals in a chert?

Answer 2

Quartz, Chalcedony, Opal

Question 3

What are the minor minerals in a chert?

Answer 3

Clay minerals, Hematite, Dolomite, Organic Matter

Question 4

Chert is commonly _________, deeper than CCD

Answer 4

Pelagic

Question 5

True or False: Chert is host to petroleum, phosphorites, uranium, and manganese.

Answer 5

True

Question 6

The types of quartz that comprises chert are:

Answer 6

MicroQuartz
MegaQuartz
Chalcedonic Quartz

Question 7

Some minor chemical elements in cherts are derived from four possible sources, which are:

Answer 7

-Biogenic
-Detrital
-Hydrogenous
-Hydrothermal

Question 8

It is a red colored chert, with trace amounts of hematite.

Answer 8

Jasper

Question 9

A chert that resembles unglazed/ unpolished porcelain.

Answer 9

Porcellanite

Question 10

Also known as nodular chert.

Answer 10

Flint

Question 11

A chert that is interbedded chert and hematite, BIF

Answer 11

Jaspilite

Question 12

A chert that is classified as dense and fine-grained

Answer 12

Novaculite

Question 13

Has low density, is light colored, associated with hot springs and is an exploration marker

Answer 13

Siliceous Sinter

Question 14

Cherts with crossbedding, laminations, ripple marks, sole marks, associated with siliceous ooze

Answer 14

Bedded Chert

Question 15

The two types of Diatomaceous Deposits are:

Answer 15

Diatomaceous Chert - Lenses pieces of diatomites in silica cement
Diatomites - Light colored, soft, friable

Question 16

Two types of Radiolarian Deposits are:

Answer 16

Radiolarian Chert - Well bedded, well developed, radiolarian fossils tend to survive diagenesis
Radiolarite - A bit harder than oozes

Question 17

Is a result of inadequate examinations, or severe diagenesis

Answer 17

Bedded Chert with few to no skeletal remains

Question 18

Cherts that are subspheroidal, masses, lenses, irregular layers, tan to black in color

Answer 18

Nodular Cherts

Question 19

Solubility of silica/chert

Answer 19

At 25°C ~11ppm for quartz, 116ppm for amorphous silica

Question 20

True or False: Silicic concentration in seawater is ~18 ppm

Answer 20

False, ~13 ppm

Question 21

The only mechanism capable of large-scale silica extraction from undersaturated seawater

Answer 21

Removal of silica from ocean water by silica-secreting organisms to build opaline skeletal structures

Question 22

Age of radiolarians

Answer 22

Cambrian/Ordovician to Holocene

Question 23

Age of Diatoms

Answer 23

Jurassic –Holocene

Question 24

Age of Silicoflagellates

Answer 24

Cretaceous –Holocene

Question 25

True or False: With undersaturated oceans, chalcedony and/or microquartz is highly unlikely to occur in purely inorganic processes

Answer 25

True

Question 26

Sufficient number of the siliceous skeletons may survive total dissolution to accumulate on the seafloor as?

Answer 26

Silicon Oozes